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Rats repeatedly exposed to the bar test following injections with a dopamine D2-like receptor antagonist such as haloperidol show increased descent latencies, suggesting that contextual stimuli may lose their ability to elicit approach and other responses. Here, we showed that rats took progressively longer to initiate descent from a horizontal bar across sessions following daily intraperitoneal treatment (paired group) with the D2-like receptor antagonist, spiroperidol (0.125 and 0.25 mg/kg), but not in the control group that received 0.25 mg/kg in their home cage and testing following saline. When both groups were tested following an injection of spiroperidol or following saline, a sensitized and a conditioned increase in descent latency, respectively, were observed in the paired but not in the unpaired group. No evidence of sensitization or conditioning was found with the substituted benzamide compound, eticlopride (0.15-0.5 mg/kg), or the D2-like receptor partial agonist, aripiprazole (0.25-0.5 mg/kg). The different effects of these agents on learning may be related to different region-specific affinities for dopamine receptors or differences in receptor dissociation profiles. We suggest that the behavioural changes observed in spiroperidol-treated rats may reflect inverse incentive learning.

Summary Considerable evidence suggests that at least some of the effects of ethanol are mediated by an action on the GABAA receptor chloride channel complex. More speculative is the suggestion that ethanol might interact with endogenous ligands for the benzodiazepine receptor on the complex. This paper considers the evidence for such interactions.

The present study investigated the effects of early postnatal handling and temporary maternal isolation, between the 5th and 20th postnatal days, on various behaviors related to stress measured in adulthood in male Wistar rats. In addition, β-adrenoceptor binding in the brain was measured. The handling consisted of daily 3-min sessions during which a pup was gently held by an investigator. The isolated rat pups were kept separated from their nursing mothers for 1 h daily. Subsequently, it was found that the time spent immobile in Porsolt's swim test was shortened, and voluntary alcohol (5% v/v) consumption was reduced in the handled rats, as compared with the non-handled and isolated animals. No differences in the measure of anxiety — food consumed in a novel environment — or the time spent in social, aggressive and defensive behaviors in a resident-intruder paradigm, were noted. Neither did the density or affinity of β-adrenoceptors in the frontal cortex or hippocampus differ significantly between the groups. The results indicate that short-lasting maternal separation does not cause sustained effects on behavior in the rat. Early postnatal handling leads to shortened immobility in the swim test and reduced voluntary alcohol consumption, suggesting that handled rats show an improved ability to cope with stress.

The effect of tryptophan on immobility in Porsolt's swim test was studied in male NIH Swiss mice. Preexposure to a swim or fight-stressor was included in the design. Doses of tryptophan (0, 12.5, 50, 75, 100, 125 and 200 mg/kg) were administered intraperitoneally 60 min prior to the swim test. In the nonstressed mice tryptophan had an U-shaped dose-response relationship: immobility in the water was dose-dependently shortened after doses from 0 to 100 mg/kg, whereas after 125 and 200 mg/kg tryptophan the immobility times did not differ from the values obtained after a saline injection. Preexposure to a swim- or fight-stressor did not make mice more sensitive to the effects of tryptophan. Tryptophan (0-300 mg/kg) had no effect on exploratory behavior or locomotor activity in the holeboard, suggesting that sedation was not a factor in the swim test results. The findings suggest that tryptophan has antidepressant -like properties in Porsolt's swim test.

The behavior of isolated Cr:NIH(S) mice (Mus musculus) was studied in a holeboard test of exploration, in a plus-maze test of anxiety, in the resident-intruder paradigm of aggression, and in the swim test. Thereafter, mice that were matched for body weight were housed together in groups of 4-5. Within a week, 1 mouse per cage (the alpha) had attacked all its subordinate cagemates but lacked any signs of attack itself. Subordinate mice had bite marks on their tails and backs. When mice were isolated, no differences were found between the behavior of those that later became alphas and those that became subordinates. In contrast, after the establishment of the social hierarchy, alpha mice spent less time immobile in the swim test and had higher locomotor activities than did the subordinate mice. The results suggest that the differences in behavior between the alpha and subordinate mice result from aggressive social interactions in the home cage.

The effects of two structurally different inhibitors of phenylethanolamine-N-methyltransferase, LY 134046 and CGS 19281A were investigated in a holeboard test of directed exploration and locomotor activity. Both compounds dose-dependently reduced exploratory head-dipping without affecting locomotor activity. The interaction of each drug with ethanol was also studied by testing the ataxia. Administration of these compounds had differential effects in a test of ethanol-induced ataxia. LY 134046 significantly attenuated ethanol-induced ataxia whereas CGS 19281A was without effect or (at 50 mg kg-1) potentiated ethanol's effect. These results suggest that the ethanol attenuating properties of LY 134046 may not solely be due the inhibition of PNMT and that its alpha 2-adrenoceptor blocking properties may be playing a role.

Dominant rats are found to consume less alcohol than their subordinate cage-mates. It is unclear whether the difference is due to dominant, aggressive animals consuming low levels of alcohol or whether social stress increases alcohol intake in subordinate animals. The present study investigated alcohol drinking patterns in aggressive alpha mice, their fight-stressed submissive cage-mates and non-fighting control mice before and after the establishment of social hierarchies. The results revealed that both moderately and severely fight-stressed submissive mice showed increased consumption of 5% alcohol, expressed as g/kg, but only severely wounded submissive mice showed increased alcohol preference over total fluid consumption, as compared with alpha mice. The difference in alcohol consumption was not seen prior to the establishment of submissive and alpha status, indicating that the submissive mice increased their alcohol consumption only after experiencing fight-stress. The amount of alcohol consumed did not differ between alpha and non-fighting control mice. To further investigate the possible connection between alcohol intake and aggressivity, the mice were studied in the resident-intruder test before group-housing. The results failed to show a consistent pattern of correlations between the time spent in aggression in this test and subsequent alcohol intake measures. The data indicate that severe fight-stress increases alcohol consumption in mice. Alcohol intake of aggressive, dominant alpha mice is not significantly altered, as compared with non-fighting animals. Furthermore, the level of aggressiveness prior to the establishment of social status does not directly affect alcohol consumption. These results suggest that aggression and dominance are not critical in determining alcohol intake patterns, whereas being a target of severe social and physical stress significantly elevates alcohol consumption in mice.

The role of central adrenoceptors in the ethanol-attenuating effects of alpha-2 adrenoceptor blockers was investigated in mice; the centrally active antagonist atipamezole was compared with L 659,066, which penetrates the brain poorly. L 659,066 (1-10 mg/kg) had no effect on the hypothermia induced by ethanol (2 g/kg) or ethanol ataxia (2.4 g/kg), whereas atipamezole (1 mg/kg) significantly attenuated both ethanol-induced hypothermia and ataxia. Atipamezole (1-3 mg/kg) significantly attenuated the ethanol-induced reduction in exploratory head-dipping in a holeboard test whereas L 659,066 was only effective at a dose of 1 mg/kg, higher doses (3 and 10 mg/kg) and a lower dose (0.3 mg/kg) were ineffective. Atipamezole was without effect on ethanol's locomotor stimulant effect in the holeboard but L 659,066 attenuated this effect at doses less than 3 mg/kg Many alpha-2 adrenoceptor ligands also have affinity for nonadrenergic imidazoline-binding sites. The role these sites may play in attenuating ethanol's effects was investigated by comparing RX 821002 (methoxy idazoxan), which has little or no affinity for imidazoline-binding sites with atipamezole. Both atipamezo 1 e (1 mg/kg) and RX 821002 (0.06-0.2 mg/kg) significantly attenuated ethanol-induced hypothermia, ataxia and reduction in head-dipping, but were without effect on ethanol-induced locomotor stimulation. These results suggest that nonadrenergic imidazoline-binding sites are not implicated in the ethanol-attenuating properties of alpha-2 adrenoceptor antagonists.

We recently reported that measurements of the maximal velocity of pulmonary endothelial angiotensin-converting enzyme (Vmax) in vivo provide information regarding microvascular surface area in the developing lamb. To obviate any subtle influences of development on Vmax aside from simple increases in surface area, we correlated Vmax with postmortem stereological assessments of alveolar surface area in the relatively mature lung of the 2-mo-old lamb (n = 14). We attempted to increase the range of surface area beyond its normal variability by injecting nine of the lambs with bleomycin, an antineoplastic agent with significant pulmonary toxicity in other species. Vmax, measured shortly after birth and then weekly, increased monotonically in all lambs. Despite their wide dispersion, Vmax and the stereological determinations correlated strongly at 2 mo of age, confirming that Vmax is a robust indicator of the surface area of the air-blood barrier. There was no significant difference in either measurement between the control lambs and those treated with bleomycin, suggesting that the newborn lamb is resistant to the effect of this agent.

The centrally active inhibitors of phenylethanolamine-N-methyltransferase (PNMT), LY 78335 and LY 134046, were investigated both alone and in combination with ethanol (2 g/kg) in a holeboard test of directed exploration and locomotor activity. Both PNMT inhibitors showed dose-related reductions in exploratory head-dipping but were without effect on locomotor activity. In combination with ethanol both PNMT inhibitors tended to attenuate the ethanol-induced reductions in exploratory head-dipping but did not effect ethanol's locomotor stimulant properties. LY 134046 showed neither an anxiolytic nor an anxiogenic profile in the plus-maze test of anxiety, nor did it alter the anxiolytic effects of either 1.2 g/kg or 2 g/kg ethanol. LY 134046 did, however, attenuate the ataxic effects of a 2.4 g/kg dose of ethanol. These results may suggest a role for adrenaline synthesis in some, but not all, of the behavioral effects of ethanol.

An overview of ethologically-based animal models suitable for investigating the pharmacological treatment of anxiety disorders is presented. The DSM-IIIR classification provides a framework for the discussion. The limitations of the models in current use are considered. It is suggested that there is a need for a greater emphasis on animal models of anxiety with an etiological basis.

We lowered cardiac output progressively in a controlled, stepwise fashion in conscious, unsedated lambs to determine the critical cardiac output or systemic oxygen delivery (the level at which oxygen consumption decreased abruptly). With the use of incremental inflation of a balloon-tipped catheter placed in the right atrium to lower cardiac output, we examined the response of oxygen consumption, systemic oxygen transport, fractional oxygen extraction, arterial lactate, and blood pressure. We studied lambs at 2 (n = 5), 4 (n = 5), and 8 wk (n = 6) of age and found that the 4-wk-old lambs reached critical values of cardiac output and systemic oxygen transport with the smallest proportional decreases from base-line values. Therefore, the 4-wk-old lambs were the least tolerant of acute decreases in cardiac output. We also found that fractional oxygen extraction was able to increase even after critical systemic oxygen transport was achieved. Furthermore, we found at every age that lactic acid accumulation began when the critical level of cardiac output was reached.

In the mouse, there is evidence that a single genetic locus is a major determinant of differences in ethanol intake between some preferring and non-preferring inbred strains. In this report, we present evidence from two independent experiments indicating that this locus maps to chromosome 1 and that its expressed product is the abundant protein LTW-4 (a 28 kDa, pI 5.6 protein expressed in brain, liver and kidney). The genetic association was found using a panel of 14 polypeptides of mouse brain which were visualized by two-dimensional electrophoresis and which exhibit genetic variation in isoelectric point. Fifteen BXD recombinant inbred strains and the two parental strains were typed for these loci and also tested for ethanol acceptance. Strains exhibiting the basic allele showed significantly higher ethanol acceptance. When 19 distantly related inbred mouse strains were tested for ethanol acceptance and typed for LTW-4, it was again found that strains exhibiting the basic allele showed significantly higher ethanol acceptance.

The 5HT uptake inhibitor fluoxetine had no effect on motor activity or directed exploration (head-dipping) in a holeboard test or in an elevated plusmaze test of anxiety. Fluoxetine (20 mg/kg) attenuated the anxiolytic effect of a 2.4 g/kg dose of ethanol in the plusmaze but failed to alter ethanol's effects on exploratory head-dipping or locomotion. This interaction did not seem directly related to fluoxetine's 5HT uptake inhibiting properties because it was not observed with other 5HT uptake inhibitors (fluvoxamine and citalopram). Desipramine, which predominantly inhibits noradrenaline uptake, also failed to show effects similar to those of fluoxetine.

The effects of two selective alpha 2 -adrenoceptor agonists (clonidine and medetomidine) and antagonists (atipamezole and idazoxan) were examined in the holeboard test. The interactions of the two antagonists with ethanol were also investigated. Atipamezole (0.1–3.0 mg/kg) and idazoxan (0.01–0.3 mg/kg) were without effect on either directed exploration or locomotor activity in the holeboard test, whereas clonidine (0.003–0.1 mg/kg) and medetomedine (0.003–0.1 mg/kg) were sedative. Atipamezole (1–3 mg/kg) and idazoxan (0.3–1.0 mg/kg) reversed the behavioral effects of 0.1 mg/kg of medetomidine. When administered with ethanol (2 g/kg), atipamezole (1–3 mg/kg) showed a significant antagonism of the ethanol-induced reduction in exploratory head-dipping: no change in the locomotor stimulant properties of ethanol was seen. A similar trend was seen for exploration after a combination of idazoxan (1–3 mg/kg) with 2 g/kg ethanol; however, the 3 mg/kg dose attenuated the locomotor stimulant effect. Both antagonists caused a dose-related reduction in the increase in head-dipping seen after administration of 1 g/kg of ethanol, without any effect on the locomotor stimulant effect of this dose. These results suggest mediation of alpha 2 -adrenoceptors in some of the behavioral effects of ethanol.

1. The proconvulsant effects of the imidazodiazepine Ro 15-4513, were investigated in mice by use of intravenous infusion of a variety of convulsant drugs. 2. Dose-response and time course studies of Ro 15-4513 against gamma-aminobutyric acid (GABA) antagonists were performed. On the basis of these studies a maximally effective dose of 5 mg kg-1 was administered 5 min before the determination of seizure thresholds in subsequent experiments. 3. Ro 15-4513 (5 mg kg-1) significantly lowered seizure thresholds to pentylenetetrazole, bicuculline and the convulsant benzodiazepine Ro 5-3663, but failed to alter seizure thresholds to picrotoxin, strychnine, caffeine and quipazine. 4. Ro 15-4513 significantly raised seizure threshold to the benzodiazepine receptor inverse agonist methyl 6,7-dimethoxy-4 ethyl-beta-carboline-3-carboxylate (DMCM). 5. These results are discussed in relation to other studies investigating the proconvulsant and alcohol-antagonizing effects of Ro 15-4513.

The ability of the imidazodiazepine Ro 15-4513 to antagonize the anticonvulsant effects of diazepam, sodium pentobarbital and ethanol was investigated. Ro 15-4513 alone significantly lowered seizure threshold to bicuculline and this effect subtracted from the anticonvulsant effects of sodium pentobarbital and ethanol. In contrast, Ro 15-4513 completely reversed the anticonvulsant effects of diazepam, consistent with suggestions that it is a competitive ligand for benzodiazepine receptors.

Rats tested on two occasions in a holeboard apparatus showed between-session habituation of exploratory activity. No habituation was observed on the measure of locomotor activity. Administration of chlordiazepoxide before the first test reduced exploratory behavior in this test and also reduced the degree of between-session habituation. Administration of RO 15–1788 reversed the effect of chlordiazepoxide on exploration in the first test, but failed to reverse the drug's effect on between-session habituation. It is unlikely that state-dependent retrieval could account for these results. The results are discussed in relation to the effects of benzodiazepines on learning and memory.

The interaction of a highly potent and selective alpha-2 adrenoceptor antagonist, atipamezole with ethanol was investigated in tests assessing a number of ethanol's behavioral effects. Atipamezole antagonized ethanol's effects on directed exploration in a holeboard test, reduced observer-rated intoxication and also reduced the duration of loss of righting reflex caused by ethanol. Similar effects were produced by another alpha-2 adrenoceptor antagonist idazoxan. The magnitude of the effects was comparable to that produced in the same animal models by the imidazodiazepine Ro 15-4513, which antagonizes ethanol by an action at central benzodiazepine receptors. Whereas Ro 15-4513 possesses marked behavioral effects on its own, atipamezole is comparatively inactive in all paradigms so far tested. The data suggest that alpha-2 adrenoceptors can play an important role in modulating the intoxicating effects of ethanol.

The effects of the imidazothienodiazepinone Ro 19-4603 were investigated in mice. Ro 19-4603 (0.03–0.3 mg/kg) caused a dose-related reduction in seizure threshold to i.v. bicuculline. Doses of 0.1–3 mg/kg induced seizures in some but not all mice, consistent with its suggested action as a partial benzodiazepine receptor inverse agonist. Ro 19-4603 (0.01–0.3 mg/kg) attenuated the intoxicating effects of ethanol (2.4 g/kg) and was as effective as Ro 15-4513 in this respect.

The effects of ethanol (0.8-2.4 g/kg) on exploratory behavior and its habituation were investigated by testing DBA/2 mice in a holeboard apparatus. Mice familiar with the holeboard had lower levels of exploration than animals with no previous experience in the apparatus. If the animals received ethanol during their first exposure to the holeboard they did not show the same degree of habituation. Ethanol (0.8 g/kg) increased the exploration of animals naive to the holeboard, but failed significantly to increase the exploration of animals familiar with the apparatus. An increase in locomotor activity was observed following treatment with ethanol (2.4 g/kg). This was potentiated if animals received a single treatment with ethanol 3 days earlier, but only if they were tested in the apparatus following the initial treatment. These results have important implications for the design of experiments investigating tolerance and sensitization to ethanol's effects on locomotor activity and exploration.

A series of experiments was performed to examine the effects of two benzodiazepine antagonists, flumazenil and ZK 93426, on the behavioral changes caused by ethanol (2 g/kg) in a holeboard test. The interaction between ethanol and low doses of diazepam (0.2 and 0.5 mg/kg) was also investigated. Both flumazenil and ZK 93426 reversed the reduction in exploration caused by ethanol, but tended to increase exploration when administered alone. In contrast, diazepam, which also increased exploration alone, tended to enhance the reduction in exploration caused by ethanol. Diazepam reduced the motor stimulant action of ethanol. The partial reversal by the two antagonists of the reduction in exploration caused by ethanol was not due to alterations in blood ethanol concentrations but may have resulted from their intrinsic exploration-increasing effects or an antagonism of an endogenous ligand for central benzodiazepine receptors.

The effects of three quinoline derivatives, PK 8165 (7.5 mg/kg), PK 9084 (7.5 mg/kg) and CGS 8216 (1 and 10 mg/kg), alone and in combination with chlordiazepoxide (5 mg/kg), were investigated in the social interaction test of anxiety. PK 8165 had no effect on social interaction but both PK 8165 and PK 9084 in combination with chlordiazepoxide produced sedation. PK 9084 exhibited a partial anxiolytic profile reflected by a drug × light interaction in the familiar test conditions. CGS 8216 (1 mg/kg) showed no significant effects on social interaction, but did counteract the sedative effect of chlordiazepoxide. The 10 mg/kg dose of 8216 reduced social interaction between pairs of animals in familiar test conditions which is indicative of an anxiogenic effect. These intrinsic anxiogenic properties of CGS 8216 demonstrate that if cannot be considered an inert benzodiazepine antagonist.

Apparent enzyme kinetics were determined for pulmonary angiotensin-converting enzyme (ACE) as a function of postnatal development and alveolar hypoxia in intact conscious lambs (9 newborn and 7 sheep, 8–23 wk). We injected into the right atrium a mixture of indocyanine green and 3H-labeled benzoyl-phenylalanyl-alanyl-proline (BPAP), a synthetic substrate for ACE, and sampled blood from the aorta at 1-s intervals. From this, we quantified the %BPAP metabolism during a single pass through the lungs by use of indicator-dilution techniques. By adding unlabeled BPAP to the injectate, combining outflow data from two to three measurements, and applying a nonlinear model of pulmonary metabolism (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 51:405–414, 1981), we could determine 1) apparent maximum velocity (Vmax); 2) concentration at which velocity was one-half Vmax (Km); and 3) alpha, a measure of perfusion heterogeneity. All animals were studied during normoxia and while breathing 10% O2 for at least 15 min. Seven of the newborn lambs were studied 1 wk later. Km in the newborn was 15 +/- 3 microM and did not change significantly with age or hypoxia. Vmax increased markedly with development (newborn: 14 +/- 2 nmol X s-1 X g dry lung-1; sheep: 38 +/- 5 nmol X s-1 X g dry lung-1; P less than 0.01). Alveolar hypoxia significantly decreased Vmax in the newborn only (P less than 0.05); there was no significant change in Vmax in the same animal studied 1 wk later or in the older group.(ABSTRACT TRUNCATED AT 250 WORDS)

Ethanol (2 g/kg) reduces the time spent in social interaction and increases locomotor activity of pairs of NIH Swiss mice. This study examined whether two benzodiazepine receptor inverse agonists, RO 15-4513 (3 mg/kg) and FG 7142 (30 mg/kg) are able to reverse these effects. Neither drug alone altered social behavior, but both significantly attenuated the effect of ethanol on social interaction. They did not affect the ethanol-induced increase in motor activity. Benzodiazepine receptor inverse agonists thus appear capable of antagonizing some, but not all of the behavioral effects of ethanol in this paradigm.

Treatment with 5HT reuptake inhibitors has been shown to attenuate ethanol consumption in both animals and humans. These experiments investigate in mice the interactions of the 5HT reuptake inhibitors fluoxetine, citalopram and fluvoxamine and the NA uptake inhibitor desipramine with ethanol in the holeboard test and the elevated plusmaze test of anxiety. Ethanol (2.4 g/kg) increased activity both in the holeboard and on the plusmaze, decreased both the number and duration of head-dips in the holeboard, and increased both the percentage time and percentage entries on to the open-arm of the plusmaze (reflecting its anxiolytic properties). On their own, the selective 5HT uptake inhibitors fluoxetine, fluvoxamine, and citalopram and the NA uptake inhibitor desipramine (10-20 mg/kg) did not significantly alter any of the behavioral measures. The only consistent interaction was seen with fluoxetine which reduced ethanol's anxiolytic effects at the 20 mg/kg dose without altering ethanol's effects on exploration or locomotion. The results suggest that the attenuation of ethanol's anxiolytic properties by fluoxetine may not be serotonin related since other 5HT reuptake inhibitors did not show this effect at the doses used.

The intrinsic effects of the benzodiazepine receptor ligand beta-CMC (3-(methoxycarbonyl)-amino-beta-carboline) and its interaction with the anticonvulsant and sedative effects of diazepam were assessed. beta-CMC (100 mg/kg i.p.) significantly elevated seizure threshold to bicuculline. beta-CMC (10 mg/kg) failed to alter the anticonvulsant action of diazepam (5 mg/kg i.p.), but significantly attenuated diazepam's sedative effect. A higher dose of beta-CMC (40 mg/kg) did attenuate diazepam's anticonvulsant action. The data suggest that beta-CMC is a partial agonist at benzodiazepine receptors.

It has recently been claimed that RO 15-4513 selectively opposes some of the behavioral actions of ethanol. Our studies on the intrinsic effects of this compound have shown it to be proconvulsant and to reduce exploratory behavior in mice. In these respects RO 15-4513 resembles a benzodiazepine receptor partial inverse agonist. Such intrinsic actions may well explain its alcohol-anatagonizing properties, and argue against its potential in humans. In addition to partially reversing the effects of ethanol, RO 15-4513 also partially reverses the behavioral effect of a barbiturate and completely reverses the effects of a benzodiazepine.

RO 15–1788 (4–20 mg/kg), both alone and in combination with chlordiazepoxide (5 mg/kg), increased exploratory head-dipping in a holeboard above control levels. This intrinsic action of a benzodiazepine antagonist is not reversed, and is even augmented, by chlordiazepoxide. RO 15–1788 alone had no effect on locomotor activity, but antagonized the sedative effects of chlordiazepoxide. β-CCE (1 and 2 mg/kg) was without effect on locomotor activity, but the higher dose reduced head-dipping.

The behavioural effects of n-propyl beta-carboline-3-carboxylate (beta-CCP) were assessed in the social interaction test of anxiety and in the holeboard test of exploratory behaviour. n-Propyl beta-carboline-3-carboxylate (2 mg/kg) significantly reduced the time spent in social interaction without affecting locomotor activity, indicating an anxiogenic action. This reduction was not significantly reversed by chlordiazepoxide (3 mg/kg). In the holeboard, beta-CCP (4 mg/kg) reduced exploratory head-dipping and rearing; neither of these effects was significantly reversed by chlordiazepoxide (5 mg/kg). The actions of beta-CCP in these two tests are similar to those of the structurally-related compound ethyl beta-carboline-3-carboxylate.

Intravenous injection of ethyl β-carboline-3-carboxylate (β-CCE, 2 mg/kg) significantly reduced exploratory behaviour in a holeboard and 1 & 2 mg/kg markedly reduced the number of rears made. These effects were similar to those found with chlordiazepoxide (5 mg/kg). When they were given together the two drugs neither counteracted each other's effects, nor were their combined effects additive. We suggest that β-CCE and the benzodiazepines might both act at one class of benzodiazepine receptor, as agonists to produce the same behavioural effects. The results are also discussed with reference to other intrinsic actions of these compounds.

The effects of picrotoxin (2 and 4 mg/kg) and of pentylenetetrazole (PTZ 5, 10 and 20 mg/kg) were examined in a social-interaction test of anxiety. Picrotoxin (2 mg/kg) caused a significant reduction in active social interaction, without a concomitant reduction in motor activity, indicating an anxiogenic action. Picrotoxin (4 mg/kg) and pentylenetrazole (20 mg/kg) reduced social interaction by more than 75% and motor activity by 40%. Although it is likely that the reduction in motor activity is secondary to the very low levels of social interaction, an unambiguous interpretation of an anxiogenic effect is not possible. Increased concentrations of corticosterone in plasma following administration of picrotoxin were consistent with the drug being anxiogenic. Chlordiazepoxide (5 mg/kg) significantly reversed the reductions in social interaction and locomotor activity following injection of picrotoxin (4 mg/kg) and PTZ (20 mg/kg).

The effect of postnatal development and acute alveolar hypoxia on pulmonary metabolic function was studied in conscious newborn lambs. Measurements of the ability of the lungs of these animals to metabolize [3H]benzoyl-L-phenyl-alanyl-L-alanyl-L-proline ([3H]BPAP; a synthetic substrate for angiotensin-converting enzyme, ACE) and to remove 5-hydroxy-[14C]tryptamine (5-[14C]HT) were made by modified indicator-dilution techniques during normoxic and hypoxic (fraction of inspired O2 = 0.10) conditions at 1 day, 1 wk, and 1 mo of age. Six additional sheep (8-23 wk old) were studied acutely as “adult” controls. BPAP metabolism in the 1-day-old group was 48 +/- 3% and increased slowly to 57 +/- 1% (P less than 0.05) at 1 mo of age and to 79 +/- 3% (P less than 0.01) by 23 wk of age. Pulmonary 5-[14C]HT removal was adultlike at birth (69 +/- 2%). Alveolar hypoxia significantly decreased BPAP only in the 1-day-old group (41 +/- 3%; P less than 0.05) and had no significant effect on 5-[14C]HT removal over the range of ages studied. These data demonstrate a selective and gradual postnatal development of pulmonary ACE which could be due to alterations in either the affinity or maximal capacity of pulmonary ACE, or increased endothelial cell surface area secondary to rapid growth of small blood vessels in this period. Alveolar hypoxia does not appear to closely regulate either ACE activity or 5-HT removal in conscious lambs greater than 1 day old when trace amounts of substrate are used.

The present study examined the behavioral, neurochemical and endocrinological characteristics of aggressive, male alpha-mice. These mice inflict severe bite marks on other male mice in their cage, but are not attacked themselves. The characteristics of the alpha-mice were compared with those of submissive mice, and of control mice taken from cages in which no severe fighting was observed. The behavioral tests used were Porsolt's swim test of behavioral 'despair', a plusmaze test of anxiety, a holeboard test of exploration and locomotor activity, and a test of seizure threshold to bicuculline. The alpha-mice were found to be immobile in the swim test for a shorter time than the submissive and control mice, and the submissive mice for a longer time than the controls. In the holeboard, the alpha-mice spent less time making exploratory head-dips than the other mice. Submissive mice had elevated 5-HIAA levels in the hypothalamus, hippocampus and brainstem, and the alpha mice had reduced concentrations of dopamine in the brainstem. There were no significant differences in plasma corticosterone or testosterone concentrations between the groups. These findings indicate that in alpha-mice, a number of behavioral and neurochemical characteristics appear together with the unusually high aggressiveness towards cage-mates.

The interaction between isolation and the response to ethanol was investigated with a social behavior test and a loss of righting reflex paradigm. The time a pair of mice spent in active social interaction, aggressive behavior, and avoidance-irritability showed an isolation-related increase, while locomotor activity was not affected by 0-10 days of isolation. Ethanol (0.8 g/kg) reduced the social interaction time in mice isolated for 10 days and 2.0 g/kg ethanol reduced it in all groups. Ethanol induced a locomotor stimulatory effect both in group-housed and isolated animals. An aggression-inducing effect of 0.8 g/kg ethanol was observed only in mice isolated for 5 days, while mice isolated for 10 days reduced their aggressive behavior after this dose of ethanol. The loss of righting reflex after 3.5 g/kg ethanol did not appear to vary with isolation. The results suggest that isolation alters some effects of ethanol qualitatively (e.g., its effects on aggressive behavior) but leaves other effects (e.g., its locomotor stimulant and hypnotic effects) unchanged.

The effects of three drugs, chosen for their differential effects on directed exploration and locomotion (ethanol, caffeine, and FG 7142), were examined on the locomotor activity of mice in a holeboard apparatus containing either a solid floor or one with four holes in it. The dose-related effect of all three drugs on locomotor activity was not changed by the presence of the holes, although activity was slightly higher when a solid floor was used. The results indicated that the two measures can vary independently and that the directed exploration component (head-dipping) of the holeboard test does not significantly influence the locomotor activity component.

Ro 15-4513 (1.5 mg/kg) decreased the exploratory activity of mice in a holeboard test. This effect was reversed by diazepam (1 mg/kg), ethanol (1 g/kg) and sodium pentobarbital (15 mg/kg). Higher doses of these three agents reduced the number of exploratory head-dips, and Ro 15-4513 antagonised these effects. These observations are consistent with the suggestion that Ro 15-4513 is a partial inverse agonist at benzodiazepine receptors and acts by reducing the efficacy of GABA. Ro 15-4513's interaction with ethanol in the holeboard closely resembled its interaction with the barbiturate.

In two separate research centres the ability of RO 15-4513 to protect rats against the lethal effects of ethanol (7.5 and 15 g/kg) was investigated. In neither study did RO 15-4513 offer protection against ethanol-induced lethality or the loss of righting reflex caused by these doses of ethanol. These data fail to replicate the results of an earlier report and suggest that RO 15-4513 is unlikely to be clinically useful treating acute severe ethanol toxicity.

The nature of the tolerance that develops to the sedative action of lorazepam was investigated using a hole-board apparatus. Rats treated with lorazepam (0.125, 0.25 and 0.50 mg/kg) once daily for 3 days showed similar degrees of tolerance to the effects of a test dose of 0.25 mg/kg lorazepam. Tolerance was also observed in animals treated once every 2 days with lorazepam (0.50 mg/kg). Measurement of the plasma and brain concentrations of lorazepam immediately after the behavioural test showed that this tolerance was functional and not dispositional. In contrast, the behavioural effects of lorazepam were not reduced as a result of 3 days of treatment with a sedative dose of sodium pentobarbitone (20 mg/kg), although this led to lower brain concentrations of lorazepam at the time of testing.

RO 15-4513, an imidazodiazepine that has been reported to reverse some of the behavioral effects of ethanol, was given to DBA/2 mice. Although no animals treated with a 6 mg/kg dose of this drug had seizures, 20% of animals given 20 mg/kg of this drug had tonic seizures. Ethanol withdrawal was induced in DBA/2 mice treated with 4-methyl pyrazole using an inhalation paradigm. Mice were more likely to have a seizure during ethanol withdrawal if treated with RO 15-4513 (6 mg/kg) than if they received the vehicle. These data suggest administering RO 15-4513 as an alcohol antagonist to alcoholic subjects may increase the incidence of seizures.

Methods for determining Ro 15-1788 in brain tissue were developed using gas chromatography with nitrogen-phosphorus detection, and using reverse-phase high performance liquid chromatography. Application of the methods to pharmacokinetic studies in the rat found the elimination half-life of Ro 15-1788 from rat brain to be 16 min. Ro 15-1788 was undetectable in rat plasma at the time points studied. Concentrations of Ro 15-1788 in the brain were reduced if chlordiazepoxide was coadministered.

Effects of selective alpha 2-adrenoceptor antagonists, atipamezole and idazoxan, on ethanol-induced hypothermia were investigated in mice. Ethanol significantly reduced (P less than 0.001) core temperature whilst both alpha 2-adrenoceptor antagonists were without effect when administered alone. However, both the 1 and 3 mg/kg doses of atipamezole significantly (P less than 0.05) attenuated the ethanol-induced reduction in body temperature 20 and 40 min after administration. The 3 mg/kg dose of idazoxan (but not the 1 mg/kg dose) also significantly (P less than 0.05) attenuated ethanol's hypothermic effect 20 min after administration but this effect was not statistically significant at 40 min. In a subsequent experiment using lower doses of atipamezole (0.03-1.0 mg/kg) the attenuation of ethanol-induced hypothermia caused by atipamezole was found to be dose-related. The effect of the benzodiazepine inverse agonist Ro 15-4513 on ethanol-induced hypothermia was also investigated. This compound possessed an intrinsic hypothermic action but neither attenuated nor enhanced the hypothermic effect of ethanol. These results suggest that alpha 2-adrenoceptor can, at least partially, modulate the hypothermic effects of ethanol.

The effects of caffeine and its interaction with ethanol were examined in a test of social behavior and a holeboard test of exploration and locomotion. Male mice were injected i.p. with 15, 30 or 60 mg/kg caffeine alone or in combination with 2 g/kg ethanol. The animals were then put in pairs into a familiar arena, or examined individually in the holeboard. Only the highest dose of caffeine (60 mg/kg) had a significant effect on the time spent in social interaction and motor activity in the social behavior test: both measures were reduced. The duration and frequency of avoidance-irritability behavior was dose-dependently increased by caffeine. In the holeboard, caffeine caused a dose-dependent increase in locomotor activity. 30 mg/kg caffeine reversed the ethanol-induced reduction of time spent in social interaction, and 60 mg/kg caffeine antagonized the ethanol-induced increase in locomotor activity in both the social behavior and holeboard tests. Caffeine's effects on ethanol-induced behavioral changes are compared with those of other drugs.

The social behavior of pairs of male NIH Swiss mice was assessed under a variety of experimental conditions. Increasing periods of isolation increased both the total time spent in social interaction and also increased the incidence of aggressive behavior. Familiarity with the testing arena tended to increase social behavior, but the magnitude of this effect was considerably less than that previously observed in rats. High light levels reduced social interaction. Ethanol (0.8-2.4 g/kg) caused a dose-related decrease in the total time spent in social interaction, a biphasic effect on aggressive behavior and a dose-related increase in locomotor activity. While the social interaction test in this form may not be a suitable model of anxiety in NIH Swiss mice, it should provide a useful method of assessing drug effects and investigating genetic influences on social and aggressive behavior.

Preliminary data from a study of the effects of anemia on organ blood flow showed large discrepancies between cardiac output measured with the microsphere technique and simultaneous values calculated by the Fick principle. The most likely explanation was that the reference sample drawn according to our standard procedure underestimated the microsphere concentration in arterial blood, resulting in erroneously high blood flow values. In the present experiments we compared our usual reference sample, from a small catheter advanced from a peripheral artery into the brachiocephalic artery (withdrawal rate 1.3 ml/min), with a simultaneous sample from a larger catheter withdrawn at the much higher rate (7.89 ml/min). At hematocrits above 32%, microsphere concentrations from the two catheters were similar, but below 32% the concentration of microspheres in blood from the larger catheter was 30-50% more than from the smaller. The discrepancy was not altered by changing the injection site from left ventricle to left atrium and thus was probably not the result of poor mixing within the heart. It may have been the result of nonhomogeneous distribution of microspheres within larger vessels, perhaps as a consequence of laminar flow and axial streaming of both red blood cells and microspheres during anemia. Whatever the cause, it was possible to eliminate the difference by withdrawing from the smaller catheter at a more rapid rate (2.46 ml/min).

It has been well documented that the lungs are able to remove or metabolize several vasoactive substances passing through the pulmonary circulation. One such function, the conversion of angiotensin I to angiotensin II and hydrolysis of bradykinin to inactive peptide fragments is performed by angiotensin-converting enzyme (ACE). Although a precise role of these functions for systemic vasoregulation has not been defined, measurement of pulmonary metabolic capacity has the potential for providing substantial information about the integrity and physiology of the pulmonary microcirculation. Studies are described using 3H-benzoyl-phenylalanyl-alanyl-proline (a synthetic substrate for pulmonary ACE) in developing conscious lambs and older sheep. Outflow curves from indicator dilution measurements contain information regarding apparent kinetics of ACE activity. Using a nonlinear model for saturable pulmonary metabolic functions, the derived data demonstrate a) a marked increase in Vmax, the apparent maximal velocity of ACE, with age; and b) no significant change with age in apparent Km, the concentration at which the velocity of ACE is one-half Vmax. This approach has the potential for providing a biochemical tool for examining postnatal growth of the pulmonary microcirculation as well as functional integrity of the pulmonary endothelium during a variety of conditions.

The effect of CGS 8216 (10 mg/kg) alone and in combination with the imidazodiazepine Ro 15-1788 (10 mg/kg) or ethyl-β-carboline-3-carboxylate (β-CCE 1 mg/kg) was tested in the social interaction test of anxiety. All 3 compounds were found to have an anxiogenic action. When Ro 15-1788 of β-CCE was combined with CGS 8216, no mutual antagonism of the drugs' effects was observed. The failure of Ro 15-1788 to antagonize the anxiogenic action of CGS 8216 raises the possibility that CGS 8216 might be acting at a non-benzodiazepine site.

A rapid and sensitive method is described for the determination of CGS-8216 (a pyrazoloquinoline that displaces benzodiazepines from their binding sites in the brain but which reverses some of the behavioural actions of the benzodiazepines) in plasma using high-performance liquid chromatography with ultraviolet detection. CGS-9896 serves as the internal standard. The method is applied to a pharmacokinetic study of CGS-8216 in the rat. CGS-8216 was not detectable in plasma 24 h after a single IP administration of a 10 mg/kg dose. Animals treated with five once-daily injections of CGS-8216 had plasma concentrations 30 min after the final injection that were approximately four-times those observed 30 min after a single treatment. This suggests that caution must be used in the interpretation of results from experiments using multiple administrations of CGS-8216. The compound could not be detected in brain tissue at any of the time points studied.