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Previous studies from this and another laboratory demonstrated that in utero ethanol exposure reduces 5-HT neurons and S100B-immunopositive glia that are proximal to these neurons. Our laboratory also found that these effects are prevented by maternal treatment with a 5-HT(1A) agonist. Because of S100B's important role in the development of 5-HT neurons, the present study used both in vivo and in vitro models to investigate the potential involvement of S100B with the damaging effects of ethanol and with the protective effects of 5-HT(1A) agonists. We used in situ hybridization to address whether a 5-HT(1A) agonist could potentially affect S100B mRNA in vivo. Maternal treatment with buspirone between gestation days 13 and 20 significantly increased S100B mRNA in neuroepithelium of G20 offspring of control (40%) and ethanol-fed dams (20%). However, S100B mRNA was not altered in neuroepithelium from ethanol-exposed offspring. In astroglial cultures, we examined whether ethanol reduces the release of S100B and whether a 5-HT(1A) agonist could stimulate the release of this protein. We also evaluated the effects of ethanol and ipsapirone on astroglial content of S100B. Neither the concentration of S100B in astroglial media nor astroglial content of S100B were affected by ethanol. However, treatment with 100 nM ipsapirone, a 5-HT(1A) agonist, between the 6th and 7th day in vitro, increased astroglial release of S100B 2- to 3-fold. Thus, the protective effects of a 5-HT(1A) agonist on ethanol-treated 5-HT neurons might be associated with the ability of these drugs to release the neurotrophic factor S100B from astrocytes.

Studies have shown that 5-HT1A receptor ligands modulate antipsychotic-induced catalepsy. Here, we further examined the role of intrinsic activity at 5-HT1A receptors in these effects. The anti-cataleptic effects of 5-HT(1A) receptor ligands with positive intrinsic activity [from high to low: 3-chloro-4-fluorophenyl-(4-fluoro-4-[[(5-methyl-6-methylamino-pyridin-2-ylmethyl)-amino]-methyl]-piperidin-1-yl-methanone fumaric acid salt (F 13714), eptapirone, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), 2-[4-[4-(7-methoxy-1-naphtyl) piperazino]butyl]-4-methyl-2H,4H-1,2,4-triazin-3,5-dione maleic acid salt (F 11461), buspirone, 2-[4-[4-(7-benzofuranyl)piperazino]butyl]-4-methyl-2H,4H-1,2,4-triazin-3,5-dione (F 12826), ipsapirone, and (s)-N-tert-butyl-3-(4-(2-methoxyphenyl)piperazine-1-yl)-2-phenylpropanamide hydrochloride (WAY 100135)] and negative intrinsic activity [N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide dihydrochloride (WAY 100635)] were examined. Catalepsy was induced by the classical antipsychotic haloperidol (0.63 mg/kg) and measured in the cross-legged position test and in the bar test. All 5-HT1A receptor agonists, except WAY 100135, significantly attenuated the effects of haloperidol in the cross-legged position test. All agonists had similar effects in the bar test, except ipsapirone, which failed to attenuate haloperidol-induced catalepsy. In contrast to the effects observed with the agonists, the inverse agonist WAY 100635 appeared to enhance haloperidol-induced catalepsy in both tests, in agreement with earlier findings. The maximal effects of the 5-HT1A receptor ligands to attenuate catalepsy correlated positively with the rank order of their intrinsic activity at 5-HT1A receptors (either catalepsy test: r(S)=0.92, P0.001). F 13714, which had the highest intrinsic activity, maximally inhibited haloperidol-induced catalepsy in the cross-legged position and bar tests (100% and 99% inhibition, respectively). Because the magnitude of the anti-cataleptic effects of 5-HT1A receptor ligands correlates positively with their intrinsic activity, it is likely that F 13714 has marked anti-cataleptic effects because of its high intrinsic activity at 5-HT1A receptors.

Electrophysiological studies have led to the proposal that the neurobiological mechanism(s) underlying drug therapy of anxiety and depression involve(s) regionally specific adaptations in 5-HT(1A) receptor sensitivity. Depending on the drug utilized, a decrease in sensitivity of inhibitory somatodendritic autoreceptors, an increase in sensitivity of postsynaptic receptors, or both alterations, occur after several weeks of treatment. This hypothesis was tested using N,N-dipropyl-5-carboxamidotryptamine-stimulated guanosine-5'-O-(3-thio)triphosphate ([(35)S]GTPgammaS) binding assessed by autoradiography. Rats were treated for 21 days with one of four different anxiolytic/antidepressant drugs (in mg/kg): fluoxetine (10), imipramine (10), clorgyline (1), ipsapirone (2 x 20) or saline. Three brain regions rich in 5-HT(1A) receptors were examined: the dorsal raphe (somatodendritic), the dorsal hippocampus (postsynaptic) and the lateral septum (postsynaptic). Only imipramine (+17%) and fluoxetine (+54%) significantly increased agonist-stimulated binding in the dorsal hippocampus; all drugs except imipramine significantly decreased binding in the dorsal raphe (-19 to -41%). These results generally support the concept of a net enhancement of hippocampal 5-HT neurotransmission via one or more 5-HT receptor subtypes. The most consistent effect, however, was a significant decrease in stimulated [(35)S]GTPgammaS binding in the lateral septum after all four treatments (-14 to -23%), suggesting that this may be a heretofore unrecognized common outcome of antidepressant treatment deserving further study.

Background: Serotonin (5-HT) 1A receptors are of interest in the pathophysiology of schizophrenia (SCH) and the mechanism of action of atypical antipsychotic drugs. To test the hypothesis that 5-HT 1A receptor responsivity is significantly different in patients with SCH compared to normal control subjects, the neuroendocrine study was performed using ipsapirone (IPS), a 5-HT 1A partial agonist, as a probe. Methods: Ipsapirone 0.5 mg/kg, p.o. or placebo were administered, in random order, to patients with SCH (n = 43; 32 male) and normal controls (n = 33; 21 male). Blood samples for plasma cortisol and body temperature were obtained from 30 min before to 180 min after administration of IPS or placebo. Results: Female normal control subjects had markedly greater increases in plasma cortisol following IPS than did male control subjects. The placebo response-corrected plasma cortisol response to IPS was significantly blunted in female SCH compared to female normal control subjects (p = .0001). The IPS-stimulated plasma cortisol response in male SCH did not differ from that of male normal control subjects or female SCH. There were no significant differences in the IPS-induced hypothermia in men and women or between patients with SCH and normal control subjects. Behavioral responses to IPS, including nausea, dizziness, irritability, and feeling less well, did not differ between groups. Conclusions: These results suggest that the post-synaptic 5-HT 1A receptor mediated endocrine response is diminished in female SCH compared to female normal control subjects, possibly secondary to an abnormality in intracellular signal transduction mechanism.

Previously, this laboratory demonstrated that the development of serotonin (5-HT) neurons and S100B-immunopositive glia proximal to these neurons is impaired in the offspring of ethanol-fed rats. However, maternal treatment with a 5-HT(1A) agonist, e.g., buspirone or ipsapirone, between gestational days 13 and 20 prevented most of the ethanol-associated changes to developing 5-HT neurons and S100B-immunopositive glia in offspring. The present in vitro studies examined the hypothesis that the protective effects of a 5-HT(1A) agonist on ethanol-exposed, developing 5-HT neurons are mediated in part by astrocyte-produced factors such as S100B. Primary cultures of fetal 5-HT neurons were maintained in conditioned medium (CM) that was obtained from ethanol- and buspirone-treated astrocytes. In order to assess the potential contribution of S100B to the protective effects of buspirone, a mouse monoclonal antibody to S100B was added to the CM to block the biological effects of this protein. These studies demonstrated that CM, obtained from ethanol-treated astrocytes, was unable to support normal development of 5-HT neurons; there was a significant reduction in the number of 5-HT neurons/well. However, CM that was obtained from astrocytes that were co-treated with buspirone and ethanol prevented the ethanol-associated reduction, and the protective effects of buspirone required S100B. We also investigated whether exogenous S100B could protect 5-HT neurons from damage caused by direct exposure to ethanol. Direct exposure of fetal brainstem neurons to ethanol in chemically-defined medium was associated with a significant reduction in the number of 5-HT immunopositive neurons/well. However, exogenous S100B protected 5-HT neurons from the ethanol-associated reduction. Our observations suggest that the protective effects of buspirone on ethanol-exposed, developing 5-HT neurons are mediated in part by the astrocyte-produced factor S100B.

Antagonists at substance P receptors of the neurokinin 1 (NK1) type have been shown to represent a novel class of antidepressant drugs, with comparable clinical efficacy to the selective serotonin (5-HT) reuptake inhibitors (SSRIs). Because 5-HT1A receptors may be critically involved in the mechanisms of action of SSRIs, we examined whether these receptors could also be affected in a model of whole-life blockade of NK1 receptors, i.e. knock-out mice lacking the latter receptors (NK1 -/-). 5-HT1A receptor labeling by the selective antagonist radioligand [3H]N-[2-[4-(2-methoxyphenyl)1-piperazinyl]-ethyl]-N- (2-pyridinyl)-cyclohexanecarboxamide (WAY 100635) and 5-HT1A-dependent [35S] GTP-γ-S binding at the level of the dorsal raphe nucleus (DRN) in brain sections, as well as the concentration of 5-HT1A mRNA in the anterior raphe area were significantly reduced (-19 to -46%) in NK1-/- compared with NK1+/+ mice. Furthermore, a ∼10-fold decrease in the potency of the 5-HT1A receptor agonist ipsapirone to inhibit the discharge of serotoninergic neurons in the dorsal raphe nucleus within brainstem slices, and reduced hypothermic response to 8-OH-DPAT, were noted in NK1 -/- versus NK1 +/+ mice. On the other hand, cortical 5-HT overflow caused by systemic injection of the SSRI paroxetine was four- to sixfold higher in freely moving NK1 -/- mutants than in wild-type NK1 +/+ mice. Accordingly, the constitutive lack of NK1 receptors appears to be associated with a downregulation/functional desensitization of 5-HT1A autoreceptors resembling that induced by chronic treatment with SSRI antidepressants. Double immunocytochemical labeling experiments suggest that such a heteroregulation of 5-HT1A autoreceptors in NK1 -/- mutants does not reflect the existence of direct NK1-5-HT1A receptor interactions in normal mice.

An earlier study from this laboratory found a significant reduction in the density of serotonin (5-HT) neurons in the dorsal and median raphe and in the B9 complex of postnatal day 5 (PN5) offspring of female rats that consumed ethanol on a chronic basis prior to parturition. In addition, we demonstrated that maternal treatment with the 5-HT 1A agonist ipsapirone (3 mg/kg) prevented the ethanol-associated reduction in 5-HT neurons. The present investigation examined whether there was a persistent deficit of 5-HT-immunopositive neurons in the dorsal and median raphe of the offspring of ethanol-fed dams. We also evaluated whether a lower ipsapirone dose (1 mg/kg) was protective to developing 5-HT neurons in the offspring of ethanol-fed dams. The offspring of ethanol-fed dams exhibited an apparent lasting reduction in the density of 5-HT neurons in the dorsal and median raphe. The density of 5-HT neurons in control offspring was comparable at PN5 and PN19, but at both ages the offspring of ethanol-fed dams had a significant deficit of 5-HT neurons in the dorsal and median raphe. The lack of recovery in the density of 5-HT-immunopositive neurons in the offspring of ethanol-fed dams between PN5 and PN19 suggests and that the reduction was long lasting. The protective effects of ipsapirone appeared to be dose dependent. The density of 5-HT neurons in the dorsal and median raphe of PN5 (prior study) and PN19 offspring of ethanol-fed dams that were treated with 3 mg/kg of ipsapirone between gestational day 13 (G13) and G20 was comparable to that of control offspring. However, the effects of maternal treatment of ethanol-fed dams with the 1 mg/kg dose were variable, and some abnormalities were detected in the offspring of ipsapirone-treated control dams.

The effect of 1A-serotonin receptor agonist ipsapirone (3 mg/kg) on mouse behavior was studied in the "wall" and Porsolt tests. The effects of the test drug were compared in intact animals and mice previously defeated in 20 intermale encounters (victims). Ipsapirone was ineffective in victims and effective in intact mice in the wall test. In the Porsolt test the drug prolonged stupor in victims.

Previous studies have suggested that 5-HT(1A) receptor function is linked to aggression. We studied 12 healthy men selected to have high trait levels of aggression. They filled in various self-rating measures of aggression, and underwent a double blind, crossover challenge with ipsapirone (20 mg orally) and a placebo. On both occasions, we measured the endocrine (ACTH, cortisol, growth hormone and prolactin), hypothermic and bodily symptom responses every 30 min for 180 min. We found that subjects with blunted neuroendocrine responses to the ipsapirone challenge had significantly higher self-ratings of aggression on a number of measures. The same relationship held using the bodily symptom response to ipsapirone: blunted responses were associated with higher ratings of aggression. We conclude that impaired 5-HT(1A) receptor function is associated with increased aggressiveness.

To elucidate the relative contribution of somatodendritic 5-HT1A autoreceptors and postsynaptic 5-HT1A receptor the specific anti-aggressive properties of 5-HT1A receptor agonists, the influence of the novel benzodioxopiperazine compound S-15535, which behaves in vivo as a competitive antagonist at postsynaptic 5-HT1A receptors and as an agonist at 5-HT1A autoreceptors, upon offensive and defensive aggression was investigated in wild-type rats using a resident-intruder paradigm. S-15535 exerted a potent dose-dependent decrease in offensive, but not defensive, aggressive behavior (inhibitory dose (ID)(50) = 1.11 mg/kg). This anti-aggressive profile was roughly similar to that of the potent pre- and postsynaptic 5-HT1A full agonist alnespirone (ID50 = 1.24). The drug's profound anti-aggressive actions were not accompanied by sedative side effects or signs of the "5HT-(1A) receptor-mediated behavioral syndrome," which are characteristically induced by prototypical 5-HT1A receptor agonists like 8-OH-DPAT and buspirone. The selective pre- and postsynaptic 5-HT1A antagonist WAY-100635, which was inactive given alone, abolished the anti-aggressive effects of S-15535 and alnespirone, thereby confirming the involvement of 5-HT1A receptors. Furthermore, combined administration of S-15535 and alnespirone elicited an additive anti-aggressive effect, providing further support for somatodendritic 5-HT1A receptor involvement. Finally, the postsynaptic 5-HT1A antagonistic properties of S-15535 were confirmed by showing blockade of the alnespirone-induced hypothermia, a postsynaptic 5-HT1A mediated response in the rat. These data provide extensive evidence that the anti-aggressive effects of 5-HT1A receptor agonists are expressed via their action on somatodendritic 5-HT1A autoreceptors, thereby most likely attenuating intruder-activated serotonergic neurotransmission. [Neuropsychopharmacology 23:20-33, 2000] (C) 2000 American College of Neuropsychopharmacology. Published by Elsevier Science Inc. All rights reserved.

Serotonin (5-HT) receptor agonists with high affinity for the different subtypes (i.e. 5-HT(1A-1F), 5-HT(2A-2C)) of the 5-HT(1)- and 5-HT(2) receptor families have been shown to affect ingestive behavior. It has been assumed that: (1) stimulation of hypothalamic 5-HT(2C) or 5-HT(1B) receptors leads to a behaviorally specific hypophagic effect by accelerating satiety processes; (2) stimulation of 5-HT(2A) receptors leads to a disruption of the feeding cascade; and (3) stimulation of 5-HT(1A) and 5-HT(2B) receptors leads to a hyperphagic effect. The present paper reviews studies performed with the relatively selective receptor agonists ipsapirone (5-HT(1A)), CP-94,253 (5-HT(1B)), BW 723C86 (5-HT(2B)) and ORG 37684 (5-HT(2C)), as well as the nonselective receptor agonists TFMPP (5-HT(1B/2C)), m-CPP (5-HT(2C/1B)) and DOI (5-HT(2A/2C)) in a variety of feeding paradigms in rats, both after systemic and local injection. These studies support a role for other neuroanatomical regions (i.e. brain stem) and behavioral mechanisms (i.e. appetitive processes) in the hypophagic effects of these compounds, possibly as a function of the administered dose. Studies with 5-HT receptor antagonists indicate that the proposed role of particular 5-HT(1/2) receptor subtypes in the hypophagic effects of these 5-HT receptor agonists may be more complicated than originally thought. Further characterization of the role of 5-HT(1/2) receptor subtypes in the control of ingestive behavior will require extensive pharmacological and behavioral studies, using more selective receptor agonists and antagonists and different behavioral procedures, as well as verification in transgenic animals.

Although the serotonin (5-HT)1A receptor agonist ipsapirone reduces ethanol intake in a variety of animal models of alcoholism, such effects have only been reported in models based on nonoperant behavior (e.g., two-bottle choice procedures). It was the aim of the present study to characterize the effects of ipsapirone in an operant model of alcohol self-administration. Rats were trained during daily 30-min sessions to respond for oral delivery of an ethanol solution (10% w/v) or water in a two-lever, fixed-ratio:1, saccharin-fading procedure. After establishment of stable responding, ipsapirone (0, 2.5–20 mg/kg, intraperitoneal) was tested in combination with different ethanol unit doses (0, 1.25–20%). Ethanol-reinforced responding was related to the ethanol unit dose in an inverted U-shaped manner. Ipsapirone dose-dependently decreased the number of ethanol- and water-reinforced lever responses, irrespective of the ethanol unit dose, and failed to affect ethanol preference. As there was only a minor difference between the minimal effective dose which reduced operant responding for ethanol and water (i.e., 10 and 20 mg/kg, respectively), and there was no evidence for a drug-induced left- or rightward shift of the ethanol unit dose–response curve, the effects of ipsapirone are considered to be nonselective. It is suggested that the ethanol intake-reducing effects of ipsapirone are not the result of a drug-induced interference (either of an attenuating, or potentiating, nature) with the positive reinforcing stimulus properties of alcohol.

ELECTROPHYSIOLOGICAL and biochemical approaches were used to assess possible changes in central 5-HT neurotransmission in mice that had been subjected to chronic ultramild stress for 8 weeks. This treatment produced a significant decrease in the potency of the 5-HT 1A agonist ipsapirone to inhibit the electrical activity of serotoninergic neurons in the dorsal raphe nucleus, without modifying 5-HT 1A receptor binding in various brain areas. These data demonstrate that chronic ultramild stress triggers a long term and durable functional desensitization of somatodendritic 5-HT 1A autoreceptors in mice.

Rationale: Tolerance to delay of gratification, taken to reflect impulsiveness, has been proposed to be under the preferential control of central serotonin (5-HT) processes. Objective: The present study further examined the effects of drugs which directly or indirectly alter 5-HT transmission, on behaviour controlled by a delayed positive reinforcer. Methods: Rats were given the choice in a T-maze between two magnitudes of reward: small (two food pellets) and immediate versus large (ten pellets) but delayed. When a 15-s waiting period was imposed in the arm leading to the large reward, rats selected this arm on 65–70% of the trials. This frequency was reduced to less than 40% when the large reward was delayed by 25 s. Results: In rats whose ascending 5-HT pathways had been lesioned by infusion of 5,7-dihydroxytryptamine (5,7-DHT) into the dorsal raphe, the introduction of the 15-s delay contingency resulted in a transient larger reduction of the frequency of choice of the now-delayed reward, compared to sham operated controls. In contrast, choice behaviour of rats given 5,7-DHT into the substantia nigra did not differ from controls. para-Chlorophenylalanine (pCPA, 150 mg/kg IP, daily for 3 days), a 5-HT synthesis inhibitor, bretazenil (0.5-8 mg/kg IP), a benzodiazepine (BZD) receptor partial agonist, and muscimol (0.25-1 mg/kg IP), a GABAA receptor agonist, induced a shift toward immediate reward. In contrast to the other BZDs, alprazolam (1–2 mg/kg IP) enhanced the frequency of choice of the large-but-25 s-delayed reward. Similar increased preference for the large-but-delayed reward was induced by the selective 5-HT reuptake inhibitors, fluoxetine (4–8 mg/kg IP) and fluvoxamine (4 mg/kg IP). The full 5-HT1A receptor agonist, 8-OH-DPAT (0.015–0.5 mg/kg IP) enhanced the frequency of choice of the large reward delayed by 25 s, whereas the partial agonists, buspirone (1–4 mg/kg IP), ipsapirone (0.5–1 mg/kg IP) and MDL 73005EF (1–2 mg/kg SC), and the antagonist, WAY 100635 (4 mg/kg SC), reduced the number of choices of the large reward delayed by 15 s. Unexpectedly, WAY 100635 (2 mg/kg), which had no effect on choice whatever the delay, did not counteract the increased tolerance to delay induced by 8-OH-DPAT (0.06 mg/kg) and further reduced the frequency of choice of the large-but- 15 s-delayed reward induced by ipsapirone (0.5 mg/kg). Conclusions: These effects on tolerance to delay may be accounted for by a subtle balance between the opposing functional consequences of pre- versus post-synaptic 5-HT1A receptor activation or blockade. Overall, the present results provide further support to the idea that 5-HT processes participate in the control of impulsive-related behaviour, as assessed from tolerance to delay of reward in this particular T-maze procedure.

Prior studies from this laboratory showed that in utero ethanol exposure severely retards the development of the serotonin (5-HT) system; we demonstrated a reduced concentration of 5-HT and 5-HT reuptake sites and alterations in the concentration of 5-HT 1A receptors in ethanol-exposed offspring. These investigations also found that maternal treatment with a 5-HT 1A agonist, buspirone, prevented most of the ethanol-associated damage to the developing 5-HT system. In the present investigation, we investigated whether the ethanol-associated changes in the 5-HT system are due to a reduction of 5-HT neurons and whether any changes in the density of 5-HT neurons can be prevented by maternal treatment with another 5-HT 1A agonist, ipsapirone. Using immunocytochemistry, we found that in utero ethanol exposure reduced the density of 5-HT immunopositive neurons in the dorsal raphe, median raphe and B9 neurons of postnatal day 5 (PN5) rats. In all three brain areas, the offspring of ethanol-fed, saline-treated dams exhibited a 28%–40% reduction in 5-HT neurons. Ipsapirone prevented the ethanol-induced reduction in 5-HT immunopositive neurons in the dorsal raphe, median raphe and B9 neurons. In the dorsal and median raphe of control offspring, ipsapirone did not alter the concentration of 5-HT neurons. However, this drug did reduce 5-HT neurons in the B9 region of the offspring of control-fed rats.

Serotonin (5-hydroxytryptamine, 5-HT)(1A) receptor agonism and 5-HT(2A) receptor antagonism are components in the action of some of the recently developed antipsychotic drugs, e.g., clozapine and ziprasidone. However, studies of the role of 5-HT(1A) receptor agonism in the ability of these drugs to modulate dopamine (DA) release in the nucleus accumbens (NAC), which may be relevant to antipsychotic action, are lacking. Thus, we examined the effect of clinically available agents, ipsapirone, a 5-HT(1A) receptor partial agonist, and the mixed 5-HT(1A/1B)/beta receptor antagonist S(-)-pindolol, on DA release in the NAC compared to the striatum (STR). Ipsapirone produced a biphasic effect; low dose (0.1 mg/kg) decreased, high dose (3 mg/kg) increased and intermediate doses (0.1 and 1 mg/kg) did not change DA release in the NAC, respectively. However, ipsapirone, at all doses (0.3, 1, 3, but not 0.1 mg/kg) increased striatal DA release. S(-)-pindolol (3, 10, but not 1 mg/kg) produced a comparable increase in DA release in the NAC and STR. These results suggest that the ability of lower dose of ipsapirone to decrease DA release in the NAC is more likely to be due to 5-HT(1A) receptor agonism. On the other hand, the effect of higher dose of ipsapirone on striatal DA release may be due to 5-HT(1A) receptor antagonism, as is the case with S(-)-pindolol. The mechanism and clinical significance of these results for developing antipsychotic drugs is discussed.

A reduction in core body temperature is one of the characteristic consequences of 5-HT1A receptor activation in rodents. In this study, we characterized the hypothermic effects of four 5-HT1A receptor ligands with varying affinity and selectivity at the 5-HT1A receptor. 8-OH-DPAT and flesinoxan (full agonists); ipsapirone (selective partial agonist) and eltoprazine (non selective partial agonist), all induced a dose-dependent reduction in core body temperature, which was maximal 30 min subsequent to administration. This response differed quantitatively between the agonists, in both the extent and the duration of its effects. The selective 5-HT1Areceptor antagonist WAY 100635 (0.15 mg/kg), attenuated the hypothermia induced by the partial agonists, ipsapirone (10 mg/kg) and eltoprazine (10 mg/kg). In contrast, the higher dose of WAY 100635 (1mg/kg) antagonized the effects of all agonists. This study therefore further confirms the utility of hypothermia as a simple, robust in-vivo probe of 5-HT1A receptor function.This paradigm, which was enhanced by use of specific antagonists such as WAY 100635, may prove useful for the detection and characterization of novel 5-HT1Areceptor ligands.

Extracellular and intracellular recording techniques were used to assess possible changes in the functional properties of 5-hydroxytryptamine-1A receptors in brain slices prepared from rats subjected to different stress paradigms. Whereas a 30-min restraint stress did not alter the inhibitory influence of ipsapirone on the firing of serotoninergic neurons in the dorsal raphe nucleus, the same session followed by a 24-h isolation produced a significant decrease in the potency of the 5-hydroxytryptamine-1A agonist to inhibit the electrical activity of these cells. Similarly, exposure of the animals to novel uncontrolled environmental conditions for 16 h significantly reduced the potency of ipsapirone to decrease the firing rate of serotoninergic neurons in brain stem slices. The effects of the latter two stressful paradigms were observed in slices from intact rats, but not in those from adrenalectomized animals. Intracellular recording showed that exposure of the animals to novel uncontrolled environmental conditions markedly reduced the potency of 5-carboxamidotryptamine to hyperpolarize serotoninergic neurons in the dorsal raphe nucleus and to decrease the input resistance of their plasma membrane. In contrast, the same stressful paradigm exerted no significant influence on the membrane effects of this 5-hydroxytryptamine-1A agonist on pyramidal cells in the CA1 hippocampal area. These data show that, like the direct application of corticosterone on to brain slices [Laaris N. et al. (1995) Neuropharmacology 34, 1201–1210], the stress-induced in vivo elevation of serum levels of endogenous corticosterone is associated with desensitization of somatodendritic 5-hydroxytryptamine-1A receptors in the dorsal raphe nucleus. The differential changes in 5-hydroxytryptamine-1A receptor sensitivity due to stress in the latter area versus the hippocampus further support the idea that somatodendritic and postsynaptic 5-hydroxytryptamine-1A receptors are regulated differently in the rat brain.

Winter depressions in seasonal affective disorder (SAD) are associated with central serotonergic (5-HT) dysfunction. SAD patients demonstrate rather specific, state-dependent, abnormal increases in 'activation-euphoria' ratings following intravenous infusion of the 5-HT receptor agonist meta-chlorophenylpiperazine (m-CPP). Several studies are also consistent with abnormal serotonergic regulation of the hypothalamic-pituitary-adrenal (HPA) axis in SAD. Here, we investigated the effects of the 5-HT1A receptor partial agonist ipsapirone, which produces behavioral effects and HPA-axis activation, to further characterize the 5-HT receptor subtype-specificity of these disturbances in SAD. Eighteen SAD patients and 18 control subjects completed two drug challenges (ipsapirone 0.3 mg/kg and placebo) separated by 3-5 days in randomized order. We measured behavioral responses with the NIMH self-rating scale, and plasma ACTH, cortisol, and prolactin concentrations. Compared with placebo, ipsapirone was associated with significant increases in self-rated 'functional deficit' and 'altered self-reality', and in each of the hormones. There were no differences between groups on any measures. The level of depression in SAD patients was inversely correlated with their ipsapirone-induced cortisol responses. There were significant drug x order effects on baseline 'anxiety' scores, ACTH and cortisol concentrations, such that subjects were significantly more stressed (higher 'anxiety', ACTH and cortisol) prior to their first challenge compared with their second. In conclusion, post-synaptic 5-HT1A receptors appear to function normally in SAD. The previously observed m-CPP-induced behavioral abnormality may be mediated by either 5-HT2C or 5-HT7 receptors.

The effect of the 5-HT1A agonists ipsapirone (5 mg/kg), buspirone (5 mg/kg) and 8-OH-DPAT (0.5 mg/kg) on experimental anxiety was examined in sham-operated, adrenalectomized and adrenally demedullated male rats. The animal model of anxiety used was the defensive burying test. At the doses selected, all 5-HT1A compounds produced an anxiolytic-like action by reducing the burying behavior in both sham-operated and demedullated rats. However, in adrenalectomized subjects, while 8-OH-DPAT still reduced burying behavior, ipsapirone and buspirone lost their action. Data suggest that adrenocortical secretions play a role in the anxiolytic-like actions of buspirone and ipsapirone, but not in those of 8-OH-DPAT. Buspirone and ipsapirone also produced a reduction in burying behavior latency in sham-operated animals that was not observed in adrenalectomized or adrenally demedullated rats. These data suggest that adrenaline may be participating in the action of these compounds on the burying behavior latency. Present findings support possible direct relationships between the stimulation of 5-HT1A receptors and adrenal secretions.

The present study investigated the behavioral effects of five 5-HT agonists and antagonists in the rat elevated-plus-maze using conventional and ethologically derived measures. An anxiolytic effect of the 5-HT1A agonist ipsapirone (0.25, 0.75, and 2.25 mg/kg) was detected by risk-assessment and scanning but not by percentage of open-arm entries and time spent on open arms. Anxiogenic effects of the 5-HT2C agonist TFMPP (0.1, 0.2, and 0.4 mg/kg) and 5-HT2A antagonist SR 46349B (1, 3, and 10 mg/kg) were detected by percentage of open-arm entries, time spent on open arms, scanning, end exploring, but not by risk assessment. Finally, the effects of the 5-HT3 antagonist BRL 46470 A (0.001, 0.01, and 0.1 mg/kg) and 5-HT2A/2C antagonist RP 62203 (0.25, 1, and 4 mg/kg) were scarce in both conventional and ethologically derived measures. These results are indicative that ethological measures may sometimes be more sensitive than the standard ones, and should be used together with them when assessing serotonergic or any other novel drugs in the elevated plus-maze.

The neuroendocrine effects of 5-hydroxytryptamine-1A (5-HT1A) receptor stimulation remain uncertain in humans, in respect to both anterior and posterior pituitary hormone release. This is important because these endocrine responses are often used as indications of 5-HT1A receptor sensitivity. The link between receptor stimulation and subsequent hormone release is more direct with posterior pituitary hormones because there is no intermediate hypothalamic peptide in the pathway. Theoretically, therefore, posterior pituitary hormones should be more valid indicators of central 5-HT1A receptor sensitivity. We used the 5-HT1A receptor partial agonist ipsapirone (20 mg) as an oral serotonergic challenge drug in a random-order, double-blind placebo-controlled study of 12 healthy men. Blood sampling occurred at 30 min intervals up to 180 min after the administration of drug or placebo. Ipsapirone caused clear and significant elevations in adrenocorticotrophin (ACTH), cortisol (CORT), prolactin (PRL), and growth hormone (GH) release. Peak hormone and ipsapirone blood levels both occurred at 60 min after ipsapirone administration. Release of the posterior pituitary hormone oxytocin was also stimulated, but less robustly and with more baseline variation. Temperature fell significantly more after ipsapirone than placebo. These results contrast with previous studies, which found no effect of ipsapirone on PRL and GH release in humans, but are in accordance with data using other 5-HT1A agonist drugs. The presence of an oxytocin response to ipsapirone suggests that oxytocin is a potential marker for serotonergic function in neuroendocrine challenge studies, but this awaits further study.

Buspirone and other drugs that act as 5-HT1A agonists appear to be clinically effective anxiolytics in humans, yet their anticonflict effects, though robust in pigeons, are equivocal in rodents. In the present study we examined the effects of the benzodiazepine midazolam and a series of 5-HT1A agonists on punished responding of squireel monkeys. Lever presses were reinforced according to a fixed-interval 3-min schedule; in addition, each thirtieth lever press was punished. Midazolam produced large increases in response rates, whereas none of the 5-HT1A compounds produced any increases in responding. Most of these drugs decreased response rates at the higher doses examined. Although the reasons for the discrepancy between species in the anticonflict effects of serotonergic anxiolytics cannot be specified, the different anatomical distribution of 5-HT1A binding sites across species may suggest a different functional role for this receptor.

The selective 5-HT1A receptor ligand ipsapirone (IPS) caused dose-related hypothermia in humans. The response was attenuated by the nonselective 5-HT1/2 receptor antagonist metergoline and was completely antagonized by the nonselective beta-adrenoceptor antagonist pindolol, which interacts stereoselectively with the 5-HT1A receptor. The selective beta 1-adrenergic antagonist betaxolol had no effect. The findings indicate that IPS-induced hypothermia specifically involves activation of (presynaptic) 5-HT1A receptors. Therefore, the hypothermic response to IPS may provide a convenient in vivo paradigma to assess the function of the presynaptic 5-HT receptor in affective disorders and its involvement in the effects of psychotropic drugs.

Several clinical studies suggest antidepressive and anxiolytic effects of regular aerobic exercise. To study the effects of exercise on central serotonergic receptor sensitivity, we performed neuroendocrine challenges using oral doses of meta-chlorophenylpiperazine (m-CPP, 0.4 mg/kg), ipsapirone (0.3 mg/kg) and placebo in 12 marathon runners and 12 healthy controls not practicing regular exercise. After administration of the nonselective serotonergic agonist m-CPP, which exerts a number of well-reproducible effects mainly by means of its action on 5-HT2C receptors, marathon runners showed a significantly reduced cortisol response in comparison to the control group. There was also a statistical trend toward a blunted prolactin response after m-CPP in the athlete group. In contrast, the increase of cortisol and the hypothermia observed after administration of the 5-HT1A agonist ipsapirone were of the same magnitude in both groups. The behavioral response to m-CPP or ipsapirone and the mean maximal increases of plasma adrenaline and noradrenaline did not differ between the marathon and the control group. In conclusion, exercise-induced downregulation of 5-HT2C receptors could play an important role in mediating the anxiolytic and antidepressive effects of exercise.

The anti-anxiety agent ipsapirone has been shown to have modest affinity for alpha-1 receptors. We disclose the discovery of potent alpha-1a receptor subtype selective antagonists based on the ipsapirone structure which possess selectivity versus the 5-HT receptors tested. These antagonists were obtained by tethering a saccharin ring to 4-phenyl-3-carboxyethyl piperidines. The design principles which led to this structural motif are discussed. The synthesis of key analogs, their SAR, as well as results of selected in vitro and in vivo studies are described.

Genetically selected short attack latency (SAL) and long attack latency (LAL) male wild house mice behave differently in the defensive burying test. When challenged, SAL males respond actively with more time spent on defensive burying, whereas LAL males are more passive with more time remaining immobile. The first aim of this study was to find out whether the nonpairing part of the Y chromosome (Y(NPAR)) affects the behavioral stress response in this paradigm. Second, to determine if the differential behavioral profile found in males is also present in females, SAL and LAL females were tested. Third, nonattacking and attacking LAL males were compared. Five behavioral elements were recorded: defensive burying, immobility, rearing, grooming, and exploration. Males were first tested for attack latency. The results show that the Y(NPAR) influences defensive burying. However, the size of this effect is overshadowed by the background of the mice. Furthermore, although females differed from males, they tended to demonstrate the same behavioral profile as males. Nongenetic factors may also play a role, as attacking LAL males showed more defensive burying than nonattacking LAL males. Copyright (C) 1999 Elsevier Science Inc.

Thirty-one human subjects were administered a neuroendocrine challenge with the 5-HT 1a agonist ipsapirone after completing six sessions of a laboratory measure of aggression, the Point Subtraction Aggression Paradigm © (PSAP), in order to determine if a laboratory measure of aggression was related to serotonin function. Subjects who showed more aggressive responding on the PSAP ( n =11) had a significantly blunted temperature response to ipsapirone compared to those with less aggressive responding ( n =20). There was no difference between the two groups on the cortisol response to ipsapirone. This study supports a relationship between serotonin function and aggression as measured in the human laboratory, similar to the well-documented association between self-reported aggression and serotonin.

Background: To test the hypothesis that depression is associated with an increased ratio of cholinergic to serotonergic neurotransmission, we compared the effects of pilocarpine, a muscarinic agonist, and ipsapirone, a serotonin (5-HT) 1A agonist, on electroencephalographic (EEG) sleep in depressed and healthy subjects. We hypothesized, adopting the reciprocal interaction model, that the effects on REM sleep of these probes within the same individuals are negatively correlated and unmask neurobiological changes in depression. Methods: Polysomnographic recordings were obtained in 12 unmedicated patients with a current major depression and 12 normal controls. They received placebo, pilocarpine 25 mg, or ipsapirone 10 mg (orally, 15 min before bedtime, after premedication with the peripheral anticholinergic probanthine 30 mg, double blind, counterbalanced) on three occasions. Results: Pilocarpine shortened and ipsapirone prolonged REM latency equally in both groups. These effects were not correlated. Pilocarpine decreased slow-wave sleep and EEG delta power during the first nonREM episode more in controls than in patients, and enhanced EEG sigma power equally in both groups. Ipsapirone had no significant effects on EEG power. Conclusion: These data do not support the postulate of muscarinic receptor up-regulation and 5-HT 1A receptor down-regulation in depression. The significance of blunted delta power suppression in patients following pilocarpine warrants further investigations.

FERNANDEZ-GUASTI, A. AND C. LOPEZ-RUBALCAVA. Modification of the anxiolytic action of 5-HT1A compounds by GABA–benzodiazepine agents in rats. PHARMACOL BIOCHEM BEHAV 60(1) 27–32, 1998.—The general purpose of the present study was to analyze the possible interactions between the GABA–benzodiazepine and the serotonin systems in the mediation of the antianxiety actions of 5-HT1A compounds. The anxiolytic effect of buspirone (5 mg/kg), ipsapirone (5 mg/kg), indorenate (5 mg/kg), and 8-OH-DPAT (0.5 mg/kg) was established in the rat burying behavior test. Flumazenil (5 mg/kg), but not bicuculline (2.5 mg/kg), effectively counteracted the reduction in burying behavior produced by buspirone, ipsapirone, and 8-OH-DPAT. These same 5-HT1A compounds, at subthreshold doses, produced an important reduction in burying behavior when combined with diazepam (0.25 mg/kg). The effect of indorenate was not altered by any of the antagonists and, when combined with diazepam it produced large increases in burying behavior latency. Only buspirone alone and in combination with bicuculline or flumazenil impaired motor coordination as tested in the rota rod. Data are discussed on the bases of the interaction between the GABAergic and serotonergic systems, stressing species differences and variations due to the animal model of anxiety.

Background: Lamotrigine, a new anticonvulsant, has recently been reported to be effective in treating patients with bipolar mania, depression, and schizoaffective disorder, suggesting that it is perhaps a mood stabilizer with antimanic and antidepressant properties. However, the mechanism of action underlying its efficacy in mood disorders is still unknown. Methods: To explore the role of 5-HT 1A receptors in the mechanism of action of lamotrigine, we measured the body temperature and plasma cortisol responses to a challenge with a selective 5-HT 1A receptor agonist ipsapirone in ten healthy human males. Each subject received 0.3 mg/kg of ipsapirone hydrochloride tablets at time “0”. Body temperature readings and blood samples for cortisol levels were obtained at 0, 30, 60, 90, 120, 150, 180 min. The ipsapirone challenge tests were repeated after 1 week treatment with lamotrigine (100 mg/day). Results: Treatment with lamotrigine for 1 week did not significantly alter the hypothermic or cortisol responses to ipsapirone. Limitations: The limitations of this study included small sample size, low treatment dose, short treatment interval, and lack of placebo control. Conclusions: Our findings might suggest that 5-HT 1A receptor function is not involved in the mechanism of action of lamotrigine in humans. Further placebo-controlled studies with a higher lamotrigine dose and a longer treatment interval in a larger number of subjects are needed to verify this.

The effects of the new chroman derivative, alnespirone (S 20499), which is a selective 5-HT1A receptor agonist, were investigated in an animal model of depression, the learned helplessness test. Rats previously submitted to a session of 60 inescapable electric foot shocks (learned helpless controls) exhibited a deficit in escape performance in three subsequent shuttle-box sessions. Alnespirone was administered twice daily via the oral route (2.5, 5, 10, 20 mg kg(-1) day(-1)). It was shown to protect against the elevation in escape failures caused by exposure to the uncontrollable aversive situation at 5 and 10 mg kg(-1) day(-1) p.o. (13+/-2 and 10+/-3 escape failures, respectively, vs. 9+/-2 escape failures in control rats). In addition, alnespirone had a tendency to elevate the number of intertrial crossings during the resting periods, depending on the dose and day on which the avoidance task was performed (15+/-2 intertrial crossings at the dose of 5 mg kg(-1) day(-1), vs. 5+/-2 intertrial crossings for the helpless control rats, on the second day). In comparison, imipramine (64 mg kg(-1) day(-1) p.o.) provided marked protection on all three days of the avoidance task and tended to increase the number of intertrial crossings during the resting periods on the second and the third days. It is concluded that alnespirone exerts antidepressant-like properties in the learned helplessness test in rats, in a manner similar to 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin), buspirone and ipsapirone, other 5-HT1A receptor agonists.

General anxiety in humans is treated with azaspirodecanedions, which act through a reduction of serotonin transmission. Ipsapirone also represents a serotonin (5-HT1A) receptor agonist and was under development as an anxiolytic drug. Histopathologic evaluation of animal experiments revealed cellular swelling and/or vacuolation of renal papillary and medullary collecting duct (MCD) epithelium in rats but not in dogs or mice. The changes ensued already after 1 wk of dosing and were first localized in the inner MCDs. Longer treatment periods showed that these changes proceeded from proximal to distal, approaching the papillary collecting ducts. The changes were most likely the result of altered hemodynamics in the papillary tip. Swelling resulted in partial or total papillary necrosis in some cases. Furthermore, rats treated with ipsapirone showed a sharp and transient rise in urinary endothelin excretion. Concomitantly, urinary PGE2 levels were elevated. In contrast, no elevated levels of endothelin were detected in urine samples of patients from a volunteer study, leading to the conclusion that the human kidney is not susceptible to the ipsapirone-induced alterations seen in the collecting ducts of rats.

Clinical studies suggest that 5-HT1A receptor function may be blunted in depression, while 5-HT1A agonists may possess antidepressant activity. Preclinical findings implicate changes in 5-HT1A receptor sensitivity in the mechanism of antidepressant action. The hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis in depression could be related to these observations, since 5-HT1A receptors are inhibited by glucocorticoids. To evaluate the interaction of the HPA and 5-HT1A systems, we pretreated 15 unipolar depressed patients and 12 healthy control subjects with the antiglucocorticoid ketoconazole (KTCZ) prior to administration of a test dose of the 5-HT1A agonist ipsapirone (IPS). Neuroendocrine (ACTH, cortisol, growth hormone), physiological (hypothermia), and behavioral responses to IPS were assessed. As expected, KTCZ inhibited cortisol biosynthesis, but non-HPA responses to IPS were not enhanced. This study failed to show that glucocorticoid modulation of 5-HT1A receptor function is altered in depression.

The behavioural element, stretched attend posture (SAP), is an important component of the "risk-assessment" repertoire of defensive behaviour in rodents. The present experimental paradigm was devised as a novel and simple method of eliciting high levels of SAP in mice and rats. The SAP test apparatus comprised an elevated black Perspex circular platform. A smaller clear red Perspex circular "Canopy" was supported directly above the platform by a central pillar, thus dividing the platform into an inner, dimly lit covered zone and an outer, brightly lit exposed zone. In both the rat and mouse version of this model, vehicle-treated animals exhibited a marked preference for exploring the covered zone and also exhibited high baseline levels of SAP, particularly at the covered zone boundary whilst they investigated the exposed zone. In the mouse SAP test, the benzodiazepine receptor agonists, diazepam (0.5 mg/kg s.c.) and chlordiazepoxide (2 mg/kg s.c.), and the 5-HT1A receptor agonists, buspirone (1 and 3 mg/kg s.c.), ipsapirone (3 mg/kg s.c.) and 8-OH-DPAT (0.2 mg/kg s.c.), all significantly decreased the frequency of SAP without impairing motor activity. In the rat SAP test, diazepam (0.5 mg/kg s.c.) significantly decreased, whilst the anxiogenic 5-HT2C/1B receptor agonist, mCPP (0.25 and 0.5 mg/kg s.c.), significantly increased, the frequency of SAP. Ipsapirone (3 mg/kg s.c.) induced a non-specific behavioural inhibition. These data suggest that the "Canopy" SAP test is a useful paradigm to investigate risk assessment behaviour in both rats and mice, and may provide a sensitive novel rodent model of anxiety.

The present study was aimed at examining the adaptation of presynaptic 5-HT1A autoreceptors in the dorsal raphe and of postsynaptic 5-HT1A receptors in the dorsal hippocampus during long-term administration of the 5-HT1A receptor agonist ipsapirone given either repeatedly or in a sustained fashion. Concurrent microiontophoretic application of ipsapirone did not attentuate the suppressant effect of 5-hydroxytyptamine (5-HT) on 5-HT neurons, but markedly decreased it when co-applied on CA3 pyramidal neurons in the dorsal hippocampus. Thus, ipsapirone acted as a full agonist in the dorsal raphe and as a partial agonist in the dorsal hippocampus. Ipsapirone (15 mg/kg/day, s.c. × 2 days) delivered by osmotic minipumps markedly decreased the firing activity of the dorsal raphe 5-HT neurons. After 14 days of treatment, there was a complete recovery of their firing activity and a desensitization of their somatodendritic 5-HT1A autoreceptors, as assessed using microiontophoretic applications of 5-HT and 8-hydroxy-2(di-n-propylamino)tetraline (8-OH-DPAT) onto 5-HT neurons. The same degree of desensitization was obtained when ipsapirone was administered with repeated injections (7.5 mg/kg b.i.d., s.c. × 14 days). In contrast, the two modalities of ipsapirone adminsitration left unaltered the responsiveness of CA3 pyramidal neurons to microiontophoretic applications of 5-HT and 8-OH-DPAT. In conclusion, long-term administration of ipsapirone most likely increases 5-HT neurotransmission by enhancing the tonic activation of postsynaptic 5-HT1A receptors. Therefore, the use of sustained release preparation of 5-HT1A receptor agonists should not alter their therapeutic effectiveness in anxiety and affective disorders since the same effects on 5-HT1A receptor functions were produced in this rat model by the sustained and the repeated modes of administration of ipsapirone.

1. 1. The kava-pyrones kawain and dihydromethysticin are constituents of Piper methysticum which exert anticonvulsant, analgesic and anxiolytic properties. 2. 2. In the present study the effect of these kava-pyrones were tested on field potential changes (fp) induced by omission of the extracellular Mg 2+ , recorded from the area CA1 and CA3 of the hippocampal slice preparation of guinea pigs. These fp are generated by an activation of NMDA receptors and voltage dependent calcium channels. 3. 3. Kawain and dihydromethysticin reduced reversibly the frequency of occurrence of fp in a concentration range from 5 to 40 μmol/1 and 10 to 40 μmol/1, respectively. 4. 4. Reduction of the fp frequency after addition of subthreshold concentrations of 5 μmol/1 kawain and 10 μmol/1 dihydromethysticin indicated additive actions of both drugs. 5. 5. Since the serotonin-1A agonist ipsapirone also exerts anxiolytic effects, subthreshold concentrations of kawain or dihydromethysticin were combined with a subthreshold concentration of ipsapirone in another set of experiments. Combining kawain and ipsapirone or dihydromethysticin and ipsapirone caused a reduction of the rate of fp to 0.76 and 0.81 of the baseline value, respectively. 6. 6. The findings suggest that (i) single constituents of Piper methysticum may have additive actions, (ii) that the two components kawain and dihydromethysticin may enhance the effects of the anxiolytic serotonin-1A agonist ipsapirone and (iii) that activation of NMDA receptors and/or voltage dependent calcium channels may be involved in the elementary mechanism of action of some kava-pyrones.

Effects of fluvoxamine, a relatively selective 5-HT uptake inhibitor, and ipsapirone, a relatively selective 5-HT1A agonist, were studied on the initiation and/or maintenance of the voluntary intake of alcohol, morphine, cocaine, and/or nicotine in rats using the two-bottle free-choice method. Fluvoxamine (30 mg/kg/day in the drinking fluid) when given during existing morphine consumption increased the intake of this drug (1 +/- 1 vs. 3 +/- 1 mg/kg/day) but had no effect on alcohol (2 +/- 2 vs. 2 +/- 2 g/kg/day) or cocaine (10 +/- 10 vs. 13 +/- 10 mg/kg/day) intake. Ipsapirone (10 mg/kg/day in the drinking fluid) when given during existing alcohol or morphine consumption decreased the intake of the first (2 +/- 2 vs. 1 +/- 1 g/kg/day) and increased the intake of the second drug (2 +/- 1 vs. 4 +/- 1 mg/kg/day), but had no effect on nicotine (1 +/- 1 vs. 1 +/- 1 mg/kg/day) or cocaine (7 +/- 8 vs. 7 +/- 6 mg/kg/day) intake. Ipsapirone when given before exposure to the above drugs reduced subsequent alcohol (2 +/- 1 vs. 1 +/- 1 g/kg/day) and increased subsequent morphine intake (2 +/- 2 vs. 4 +/- 1 mg/kg/day), but had no effect on the voluntary consumption of cocaine (8 +/- 7 vs. 10 +/- 6 mg/kg/day) and nicotine (1 +/- 1 vs. 1 +/- 1 mg/kg/day). These results suggest: (1) selective stimulation of 5-HT1A receptors reduces alcohol preference, (2) stimulation of all 5-HT receptors has no effect on alcohol intake, indicating the presence of inhibitory receptors, (3) stimulation of the serotonergic system in general stimulates morphine preference, (4) the serotonin system does not affect nicotine or cocaine preference and (5) the serotonergic system is not involved in the voluntary consumption of all, but-only of some drugs/chemicals of abuse. Recognition of these drug/chemical-specific sites in the brain might lead to a better understanding of differences in drug abuse patterns among humans and help in the development of specific drugs for the treatment of selective drug addictions.

The effects of acute and repeated treatment with the 5-HT 1A receptor ligand ipsapirone on hippocampal excitatory synaptic transmission and in an ultrasonic vocalization anxiety test were investigated in the rat. Synaptic responses in the CA1 region of the dorsal hippocampus of alert, freely behaving male Wistar rats were reduced after acute injection of ipsapirone (1 or 2 mg/kg, i.p.). This effect was prevented by pretreatment with the 5-HT 1A receptor antagonist WAY-100635 ( N -[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]- N -(2-pyridinyl)cyclohexanecarboxamide trihydrochloride, 0.25 or 0.5 mg/kg, i.p.) but not by the 5-HT-depleting agent para -chlorophenylalanine (300 mg/kg per day for 3 days, i.p.). WAY-100635 (0.1–0.3 mg/kg, i.p.) also blocked the acute anti-aversive effects of ipsapirone (3 mg/kg, i.p.) in the anxiety test. Repeated administration of ipsapirone (1 or 2 mg/kg per day for 7–8 days, i.p.) produced a gradual reduction in baseline synaptic transmission which was transiently reversed by WAY-100635 (0.25 mg/kg, i.p.). Ipsapirone (1 mg/kg per day for 7 days) produced a gradual and sustained reduction in the duration of vocalizations in the anxiety test which paralleled the reduction in baseline synaptic responses in the same animals. The data indicate that with repeated administration of ipsapirone, a prolongation and enhancement of the 5-HT 1A receptor-mediated reduction in hippocampal excitatory synaptic transmission occurs. This delayed effect may contribute to the sustained anxiolytic and/or antidepressant effect of ipsapirone. © 1997 Elsevier Science B.V. All rights reserved.

Serotonin (5-hydroxytryptamine, 5-HT) synthesis was determined in vivo by measuring the accumulation of 5-hydroxytryptophan (5-HTP) in rat frontal cortex after inhibition of aromatic amino acid decarboxylase by administrative of m-hydroxybenzylhydrazine (NSD 1015) (100 mg/kg, i.p.). The selective 5-HT reuptake inhibitor, citalopram, the 5-HT1A agonists, (+/-) 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), ipsapirone, gepirone and the 5-HT1A/B agonist, 7-trifluoromethyl-4(4-methyl-1-piperazinyl-pyrolo[1,2-a]-quinox ali ne (CGS 12066B), the 5-HT1A/B ligands and beta-adrenoceptor antagonists, (+/-) pindolol and (+/-) alprenolol, and the non-selective 5-HT ligands, m-chlorophenylpiperazine (mCPP) and metergoline, all inhibited the synthesis of 5-HT. The 5-HT1A/5-HT2 antagonist, spiperone, alone, had no effect on basal 5-HT synthesis, however it attenuated the effect of 8-OH-DPAT by 56% and CGS 12066B by 39% but only barely that of citalopram by 17%. The selective 5-HT1A antagonist, WAY 100635, which did not modify by itself 5-HT synthesis, had no effect on citalopram-induced reduction of 5-HT synthesis. Neither the 5-HT2 agonist, (+/-)1-(2,5-dimethoxy-4-indophenyl)-2-aminopropane (DOI) nor the 5-HT2 antagonist, ritanserin, had any effect on the synthesis of 5-HT. In addition, ritanserin did not modify the inhibitory effect of citalopram. Methiothepin was the only compound to increase 5-HT synthesis. These results suggest that the effect of citalopram on the synthesis of 5-HT is not mediated by 5-HT1A or 5-HT2 receptors and that other receptors may be involved.

The olfactory bulbectomized (OB) rat has been proposed as an animal model of depression. The following behavioural changes have been observed following bilateral olfactory bulbectomy: hyperactivity in an enclosed arena, such as the open-field; enhanced nocturnal hyperactivity in a 24-hr home cage activity monitor; deficits in memory, as shown by passive avoidance behaviour and in the Morris maze and the 8-arm radial maze; increased open arm entries in the elevated plus-maze; and changes in food motivated and conditioned taste aversion behaviour. Alterations in the noradrenergic, serotonergic, cholinergic, γ-aminobutyric acid (GABA)ergic and glutamatergic neurotransmitter systems are also associated with olfactory bulbectomy. The variety of immune changes following olfactory bulbectomy includes reduced neutrophil phagocytosis, lymphocyte mitogenesis, lymphocyte number and negative acute phase proteins, increased leucocyte adhesiveness/aggregation, monocyte phagocytosis, neutrophil number and positive acute phase proteins. An enhanced nocturnal secretion of corticosterone is observed in OB rats, which is normally suppressed by dexamethasone. The most commonly employed behavioural indicator of antidepressant activity is attenuation of the OB-related hyperactivity in the open-field. However, many of the other behavioural, neurotransmitter and immune changes have been shown to be attenuated by chronic (but not acute) antidepressant treatment. Tricyclic antidepressants (amitriptyline, desipramine), atypical agents (mianserin), selective serotonin reuptake inhibitors (paroxetine, sertraline, fluvoxamine), reversible inhibitors of monoamine oxidase A (moclobemide), as well as putative antidepressants such as 5-hydroxytryptamine 1A agonists (zalospirone, ipsapirone), noncompetitive N-methyl-D-aspartate antagonists (MK-801) and triazolobenzodiazepines (alprazolam, adinazolam), have demonstrated antidepressant-like activity in this model. As many of the changes exhibited by the OB rat are qualitatively similar to those observed in depressed patients, it may be concluded that the OB rat is a model of depression and not just a means whereby putative antidepressants may be tested.

The aim of the present study was the investigation of pretreatment effects with clonidine (0.06 mg/kg, intraperitoneal [i.p.]), lithium (1 mEq, i.p.) or quinine (0.5 mg/kg, i.p.) on the activities of various drugs acting on noradrenergic and/or serotonergic systems in the mouse tail suspension test. Drugs used in the present study included: the tricyclic antidepressants imipramine and dothiepin, the heterocyclic antidepressant trazodone, the 5-HT reuptake inhibitor (SSRI) fluoxetine, the atypical antidepressants mianserin and iprindole, the 5-HT1A receptor agonist ipsapirone, the 5-HT2A/2C receptor antagonist ritanserin, and the 5-HT3 receptor antagonist ondansetron. Clonidine, lithium and quinine differentially enhanced the effects of several psychotropic/drugs administered at sub-active doses. The activity of iprindole (32 mg/kg, i.p.) was not potentiated by pretreatment with clonidine, lithium or quinine. Our results suggest that lithium exerted additive effects via postsynaptic 5-HT1A receptor activation, quinine via potassium ion channel blockade of 5-HT3 receptors, while clonidine did so primarily via action at 5-HT2 receptors.

Publisher Summary The first compound showing anxiolytic activity was buspirone. Originally, buspirone was under development as a new type of antipsychotic, possessing dopamine D∼ antagonistic activity without inducing catalepsy. Clinically, however, buspirone was not very effective, and further development was stopped. After the discovery of its taming properties in aggressive rhesus monkeys, buspirone was reintroduced as anxiolytic. It was demonstrated that the anxiolytic activity of buspirone was due to its interaction with central 5-HT 1A receptors. Currently, a variety of 5-HT 1A receptor ligands are in clinical trials for indication anxiety. Most of these compounds—for example, gepirone, ipsapirone, tandospirone, and binospirone—act like buspirone as partial agonists at the 5-HT 1A receptor. Flesinoxan is a full agonist. Pure antagonists, such as WAY 100.635, are still in the preclinical phase of development.

Somatodendritic 5-HT1A autoreceptors play a key role in the control of the electrical and metabolic activity of serotoninergic neurons in the dorsal raphe nucleus. These neurons also possess intracellular glucocorticoid receptors which may be involved in the well established modulation of serotonin (5-hydroxytryptamine, 5-HT) metabolism by corticosterone in stressed animals. The possible mediation by somatodendritic 5-HT1A autoreceptors of such corticosterone-dependent changes in serotoninergic neuron activity was investigated using an in vitro electrophysiological approach. 5-HT1A autoreceptor-mediated inhibition of the firing of serotoninergic neurons was examined in brain stem slices from rats whose serum corticosterone concentrations had been markedly increased (+100-200%) by two different stressful conditions. Immobilization for 30 or 90 min (restraint stress) did not modify the concentration-dependent inhibition of the firing of serotoninergic neurons by the 5-HT1A receptor agonist ipsapirone. In contrast, placing the rats in novel uncontrolled environmental conditions for 16 h significantly reduced the cell response to ipsapirone, indicating a decreased sensitivity of somatodendritic 5-HT1A autoreceptors. Such a change was not observed in adrenalectomized rats subjected to the same stressful conditions. These data show that some forms of stress can reduce the 5-HT1A autoreceptor-dependent inhibitory control of the electrophysiological activity of serotoninergic neurons in the dorsal raphe nucleus. Both the nature and duration of stress seem to be critical factors for triggering the (corticosterone-dependent) mechanism(s) responsible for the functional desensitization of 5-HT1A autoreceptors in stressed rats.

In the present study, the effects of 5-HT1A receptor ligands with varying degrees of intrinsic activity at the 5-HT1A receptor were examined in the conditioned emotional response (CER) test and their effects compared to those of the benzodiazepine receptor agonists, diazepam and chlordiazepoxide. Diazepam (3.0 mg/kg) and chlordiazepoxide (3.0 mg/kg), and the 5-HT1A receptor partial agonists, ipsapirone (10.0 mg/kg) and gepirone (3.0 mg/kg), alleviated conditioned suppression of lever pressing. The 5-HT1A receptor partial agonist, buspirone (0.1-1.0 mg/kg), the 5-HT1A receptor agonist, 8-OH-DPAT (0.01-0.10 mg/kg), and the 5-HT1A receptor antagonist, WAY-100635 (0.03-3.0 mg/kg), had no effects on conditioned fear. Neither enhancing the level of food deprivation nor pretreatment with the amnesic agent scopolamine induced anxiolytic-like effects in the present CER test. The anxiolytic-like effects of ipsapirone in this test were completely reversed by WAY-100635. These results indicate that 5-HT1A agonist, but not antagonist actions, induce an anxiolytic effect in the CER test in rats.

Serotonergic neurons of the dorsal and median raphe nuclei are morphologically dissimilar. Recent results challenge previous evidence indicating a greater inhibition of dorsal raphe neurons after 5-hydroxytryptamine1A (5-HT1A) autoreceptor activation. As both nuclei innervate different forebrain territories, this issue is critical to understanding the changes in brain function induced by anxiolytic and antidepressant drugs. Using microdialysis, we examined the modifications of 5-HT release induced by the selective 5-HT1A agonist ipsapirone in both neuronal pathways. Maximal and minimal basal 5-HT values (in the presence of 1 microM citalopram) were 45.0 +/- 4.8 fmol/fraction in the median raphe nucleus and 8.4 +/- 0.4 fmol/fraction in the dorsal hippocampus. Ipsapirone (0.3, 3, and 10 mg/kg s.c.) reduced dose-dependently 5-HT in the two raphe nuclei and four forebrain areas. Maximal reductions (to approximately 25% of predrug values) were observed in cortex and striatum and in median raphe nucleus. The effects were more moderate in dorsal and ventral hippocampus (to 66 and 50% of baseline, respectively). These results are consistent with a higher sensitivity of dorsal raphe neurons to 5-HT1A autoreceptor activation. Yet the differential reduction of 5-HT release in the median raphe nucleus and hippocampus suggests the presence of complex mechanisms of control of 5-HT release in these neurons.

To determine whether ipsapirone, a 5-HT1A agonist, differentially suppresses REM sleep in depressed patients compared with normal controls, we administered placebo, ipsapirone 10 mg, or ipsapirone 20 mg in a double-blind, random order before bedtime in 18 unmedicated patients with depression and 16 age-matched, gender-matched normal controls. Compared to placebo, ipsapirone affected REM sleep measures equally in depressed patients and controls as follows: (1) increased REM latency; (2) reduced total REM percent, REM time, and REM density; and (3) delayed the onset of REM sleep. In addition, ipsapirone had similar effects in patients and controls in other sleep measures: (1) reduced total sleep time; (2) delayed sleep onset time; and (3) increased sleep latency, stage 1%, stage 2%, the amount of stage 3 & 4 sleep in the first non-REM period, and wake time after sleep onset. The study does not support the hypothesis that downregulated 5-HT1A receptors mediate the pathophysiology or sleep disturbances of depression, although further studies are needed as these patients did not differ from controls in baseline sleep measures.

The purpose of the present study was to compare the contribution of pre and postsynaptic 5-HT1A receptors to the anxiolytic effects of serotonergic1A compounds in two animal models of anxiety. To this aim, the 5-HT1A ligands buspirone, ipsapirone, indorenate, and 8-OH-DPAT were tested in the burying behavior test and the avoidance exploratory behavior paradigm in control, pCPA-treated, and 5,7-DHT-lesioned mice. p-CPA and 5,7-DHT treatments did not modify the burying behavior per se, while 5-HT1A agonists produced a significant reduction in this behavior in both p-CPA- and 5,7-DHT-lesioned animals. In the exploratory behavior paradigm, p-CPA per se but not 5,7-DHT increased the black/white transitions, interpreted as an antianxiety action. The ICV injection of 5,7-DHT blocked such effect of the 5-HT1A compounds in the avoidance exploratory behavior test. Data suggest that the effect of 5-HT1A compounds in the burying behavior test is mediated via the stimulation of postsynaptic receptors, while in the avoidance exploratory behavior paradigm these compounds act through the stimulation of the presynaptic site. Discussion is based on the differences between the animal models of anxiety.

The present series of experiments was conducted to investigate whether the previously reported ethanol intake reducing effects of the 5-HT 1A receptor agonist ipsapirone could be based on possible stimulus similarities between both compounds. Rats were trained to discriminate ethanol (12.5% w/v, 1000 mg/kg, IP) from saline in a two-lever food-reinforced drug discrimination (DD) procedure. Discrimination criterion was reached after a mean number of training sessions of 42. In subsequent generalization sessions, a dose-response curve was established for ethanol (125–1000 mg/kg, IP, ED 50 value: 355 mg/kg). In additional cross-generalization tests with ipsapirone (1–30 mg/kg, IP), stimulus substitution for the ethanol cue was not noted (maximal degree of generalization: 33%, at 10 and 30 mg/kg). To confirm the DD findings that ipsapirone does not substitute for ethanol, an alternative cross-familiarization conditioned taste aversion paradigm (CF-CTA) was utilized. In rats, 1000 mg/kg IP ethanol was used as the reference drug producing a conditioned taste aversion (CTA). It was found that preexposure to ethanol (500–1500 mg/kg, IP) dose-dependently attenuates the CTA produced by this same drug. Full familiarization was noted with 1000 and 1500 mg/kg. In contrast with this, ipsapirone (1–30 mg/kg, IP) failed to abolish ethanol-induced CTA, suggesting again that the ipsapirone stimulus complex is dissimilar to that produced by ethanol. Because the present findings indicate that, in rats, ipsapirone does not substitute for ethanol, it is suggested that the reported ethanol intake-reducing effects of ipsapirone in animal models of alcoholism are not due to simple stimulus substitution.

The ontogeny of conditioned defensive-burying behavior was studied in rats from 2 to 21 weeks of age. At early ages this parameter shows low values that gradually increase until the 11th week, decreasing steadily thereafter. Reactivity, measured by the burying-behavior latency, appeared increased in 2-week-old rats. The effect of the serotonergic1A compounds: 8-OH-DPAT (0.25 and 0.5 mg/kg), ipsapirone, buspirone, and indorenate (at 2.5 and 5.0 mg/kg) was studied at 3, 7, 11, and 21 weeks of age. All compounds produced a dose-dependent decrease in burying behavior in rats of 7 and 11 weeks, while at the Week 21, only 8-OH-DPAT and indorenate reduced it. At 3 weeks of age, burying-behavior latency was increased by all compounds, but burying behavior was not altered. Motor coordination was affected by buspirone at all ages and by 8-OH-DPAT at the Week 21. Data are discussed on the bases of the development of defensive behaviors.