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Melatonin is synthesized from serotonin and it is excreted as sulphatoxymelatonin in urine. We aim to evaluate urinary sulphatoxymelatonin as a biomarker of brain serotonin status in a cohort of patients with mutations in genes related to serotonin biosynthesis. We analized urinary sulphatoxymelatonin from 65 healthy subjects and from 28 patients with genetic defects. A total of 18 patients were studied: 14 with autosomal dominant and recessive guanosine triphosphate cyclohydrolase-I deficiency; 3 with sepiapterin reductase deficiency; and 1 with aromatic L-amino acid decarboxylase deficiency. Further 11 patients were studied after receiving serotoninergic treatment (serotonin precursors, monoamine oxidase inhibitors, selective serotonin re-uptake inhibitors): 5 with aromatic L-amino acid decarboxylase deficiency; 1 with sepiapterin reductase deficiency; 3 with dihydropteridine reductase deficiency; and 2 with 6-pyruvoyltetrahydropterin synthase deficiency. Among the patients without therapy, 6 presented low urinary sulphatoxymelatonin values, while most of the patients with guanosine triphosphate cyclohydrolase-I deficiency showed normal values. 5 of 11 patients under treatment presented low urine sulphatoxymelatonin values. Thus, decreased excretion of sulphatoxymelatonin is frequently observed in cases with severe genetic disorders affecting serotonin biosynthesis. In conclusion, sulphatoxymelatonin can be a good biomarker to estimate serotonin status in the brain, especially for treatment monitoring purposes.

Neurotransmitter:sodium symporters (NSSs) are integral membrane proteins responsible for the sodium-dependent reuptake of small-molecule neurotransmitters from the synaptic cleft. The symporters for the biogenic amines serotonin (SERT), dopamine (DAT), and norepinephrine (NET) are targets of multiple psychoactive agents, and their dysfunction has been implicated in numerous neuropsychiatric ailments. LeuT, a thermostable eubacterial NSS homolog, has been exploited as a model protein for NSS members to canvass the conformational mechanism of transport with a combination of X-ray crystallography, cysteine accessibility, and solution spectroscopy. Despite yielding remarkable insights, these studies have primarily been conducted with protein in the detergent-solubilized state rather than embedded in a membrane mimic. In addition, solution spectroscopy has required site-specific labeling of nonnative cysteines, a labor-intensive process occasionally resulting in diminished transport and/or binding activity. Here, we overcome these limitations by reconstituting unlabeled LeuT in phospholipid bilayer nanodiscs, subjecting them to hydrogen-deuterium exchange coupled with mass spectrometry (HDX-MS), and facilitating interpretation of the data with molecular dynamics simulations. The data point to changes of accessibility and dynamics of structural elements previously implicated in the transport mechanism, in particular transmembrane helices (TMs) 1a and 7 as well as extracellular loops (ELs) 2 and 4. The results therefore illuminate the value of this strategy for interrogating the conformational mechanism of the more clinically significant mammalian membrane proteins including SERT and DAT, neither of which tolerates complete removal of endogenous cysteines, and whose activity is heavily influenced by neighboring lipids.

We developed a method to detect biogenic amines and their metabolites in rat brain tissue using simultaneous high-performance liquid chromatography and a photodiode array detection. Measurements were made using a Hypersil Gold C-18 column (250 × 2.1 mm, 5 µm). The mobile phase was 5 mM perchloric acid containing 5 % acetonitrile. The correlation coefficient was 0.9995-0.9999. LODs (S/N = 3) and LOQs (S/N = 10) were as follows: dopamine 0.4 and 1.3 pg, 3, 4-dihydroxyphenylacetic acid 8.4 and 28.0 pg, serotonin 0.4 and 1.3 pg, 5-hydroxyindolacetic acid 3.4 and 11.3 pg, and homovanillic acid 8.4 and 28.0 pg. This method does not require derivatization steps, and is more sensitive than the widely used HPLC-UV method.

The content of biogenic amines and their metabolism in the ancient part of the amygdala (paleoamygdala) differ in male and female rats and depended on the phase of the estrous cycle.

Serotonin (5-hydroxytryptamine; 5-HT) is an important brain neurotransmitter that is implicated in mental and neurodegenerative diseases and is modulated by ovarian hormones. Nevertheless, the effect of oestrogens on 5-HT neurotransmission in the primate caudate nucleus, putamen and nucleus accumbens, which are major components of the basal ganglia, and the anterior cerebral cortex, mainly the frontal and cingulate gyrus, is not well documented. The present study evaluated 5-HT reuptake transporter (SERT) and 5-HT metabolism in these brain regions in response to 1-month treatment with 17β-oestradiol in short-term (1 month) ovariectomised (OVX) monkeys (Macaca fascicularis). SERT-specific binding was measured by autoradiography using the radioligand [³H]citalopram. Biogenic amine concentrations were quantified by high-performance liquid chromatography. 17β-Oestradiol increased SERT in the superior frontal cortex and in the anterior cingulate cortex, in the nucleus accumbens, and in subregions of the caudate nucleus of OVX monkeys. 17β-Oestradiol left [³H]citalopram-specific binding unchanged in the putamen, as well as the dorsal and medial raphe nucleus. 17β-Oestradiol treatment decreased striatal concentrations of the precursor of 5-HT, 5-hydroxytryptophan, and increased 5-HT, dopamine and 3-methoxytyramine concentrations in the nucleus accumbens, caudate nucleus and putamen, whereas the concentrations of the metabolites 5-hydroxyindoleacetic acid, 3,4-dihydroxyphenylacetic acid and homovanillic acid remained unchanged. No effect of 17β-oestradiol treatment was observed for biogenic amine concentrations in the cortical regions. A significant positive correlation was observed between [³H]citalopram-specific binding and 5-HT concentrations in the caudate nucleus, putamen and nucleus accumbens, suggesting their link. These results have translational value for women with low oestrogen, such as those in surgical menopause or perimenopause., (© 2013 British Society for Neuroendocrinology.)

We have characterized, by intracellular recording and staining combined with immunocytochemistry, a serotonin-immunoreactive neuron in the central olfactory pathway of the male moth Helicoverpa assulta. The neuron joins the unique category of so-called SI antennal-lobe neurons, previously described in several insect species. In similarity with that originally discovered in the sphinx moth Manduca sexta, the neuron identified here has a large soma located posteriorly in the lateral cell cluster of the antennal lobe and an unbranched neurite projecting into the ipsilateral protocerebrum via the inner antennocerebral tract. After bypassing the central body, the axon crosses the midline and extends through the corresponding antennocerebral tract to the contralateral antennal lobe where it innervates the entire assembly of glomeruli including the male-specific macroglomerular complex. The neuron arborizes into several fine branches in bilateral protocerebral regions anterior to the calyces of the mushroom bodies, particularly on the contralateral side. The physiology of the neuron revealed 2 distinctly different spiking amplitudes, 1 small showing a relatively high spontaneous activity and 1 large showing low activity. The small-amplitude spikes displayed increased frequency when pheromones and plant odors were blown over the antenna. The large-amplitude spikes, which had an unusually long duration, showed no observable responses.

Intraperitoneal injection of para-chlorophenylanine (pCPA) (400 mg/rg) causes changes in the quantitative distribution of biogenic amines (BA), in olfactory bulbs, amygdaloid complex, hippocampus, and hypothalamus of the rats. Following 18 hours after injection of pCPA content of serotonine (5-HT) in olfactory bulbs drops and noradrenaline (NA) - 5-HT ratio increases. Abrupt decrease of 5-HT in all the studied structures and increase of NA - 5-HT ratio was also observed 36 hours after the pCPA injection. After 54 hours the drug effect decreased and by 72 hours the ratio was balanced. The biochemical changes taking place 36 hours after the intraperitoneal injection of pCPA in olfactory bulbs and hypothalamus probably cause concentration and ratio changes of BA, within the limits of which rats display their aggressive behavior and become "killers".

Rationale: Associative learning during Pavlovian eyeblink conditioning has been shown to be regulated by 5-HT2A receptors. The existence of inverse agonists that retard learning through an action at the 5-HT2A receptor suggests the existence of constitutive activity at that receptor and that depletion of serotonin should have minimal effects on learning., Objectives: We examined whether depletion of serotonin would impair trace eyeblink conditioning or the enhancement of conditioning produced by the agonist lysergic acid diethylamide (LSD) and the retardation of conditioning produced by the inverse agonist MDL11,939., Methods: Animals received bilateral intraventricular injections of 5,7-dihydroxytryptamine (5,7-DHT) at doses of 760 or 1,140 microg/side (1.88 or 2.82 micromol/side) and were later exposed to eight daily conditioning sessions., Results: Serotonin depletion produced by the lower dose of 5,7-DHT was 71 and 72% in cortex and hippocampus, respectively, with no change in 5-HT2A receptor density, no effect on learning, and no effect on the ability of LSD to enhance and MDL11,939 to retard learning. The higher dose of 5,7-DHT produced serotonin decreases of 85 and 90% in cortex and hippocampus, respectively, accompanied by a 96% decrease in the density of the serotonin transporter, but no significant effect on learning., Conclusions: Pavlovian trace eyeblink conditioning is regulated predominantly by the constitutive activity of the 5-HT2A receptor rather than by serotonin release onto the receptor during learning. It was suggested that the 5-HT2A receptor regulates learning by modulating the release of dopamine, acetylcholine, and glutamate, transmitters known to affect eyeblink conditioning.

Tacrine is a potent and reversible inhibitor of acetylcholinesterase (AChE) in the brain. It produces tremor in animals, which is believed to be due to an increase in the brain acetylcholine level following AChE inhibition. The present study was undertaken to investigate the involvement, if any, of biogenic amines in the genesis of this motor dysfunction. Administration of tacrine (10-20 mg/kg, i.p.) produced dose- and time-dependent tremor in Balb/c mice. While in vivo inhibition of striatal AChE activity was observed only for the highest dose of tacrine, a dose-dependent increase in striatal choline acetyltransferase activity was obtained. Serotonin (5-HT) levels, as assayed following a sensitive HPLC-electrochemical procedure, were significantly increased in nucleus caudatus putamen, nucleus accumbens, substantia nigra, nucleus raphe dorsalis, olivary nucleus and the cerebellum. However, dopamine or norepinephrine levels remained unaltered in these areas of the brain. In animals treated with p-chlorophenylalanine, a specific tryptophan hydroxylase inhibitor and 5-HT depletor, tacrine failed to elevate the levels of 5-HT in the brain regions, and significantly attenuated tremor response to the drug. Tacrine-induced tremor was also significantly (83%) attenuated by 5-HT(2A/2C) receptor antagonist mianserin (5 mg/kg, i.p.), but methysergide (5 mg/kg, i.v.) could block tacrine-induced tremor only by 20%. Atropine (5 mg/kg, i.p.) antagonized tacrine-induced tremor by about 53%, but a combination of atropine and mianserin completely blocked the tremor response. These results indicate that the cholinergic tremor produced by tacrine in Balb/c mice is mediated via central serotonergic mechanisms, and stimulation of 5-HT(2A/2C) receptors plays a pivotal role in this motor dysfunction.

Objective: To measure concentrations of amines formed in the cecum of clinically normal ponies, determine amine concentrations in plasma samples collected in spring and winter, and compare concentrations of amines and serotonin in plasma samples obtained from clinically normal ponies and ponies predisposed to laminitis., Sample Population: Cecal contents obtained from 10 ponies euthanatized at an abattoir and blood samples obtained from 42 adult ponies., Procedure: Cecal contents were assayed for amines by high-performance liquid chromatography (HPLC). Blood samples were collected at various times of the year from 20 ponies predisposed to acute laminitis and 22 clinically normal ponies. Plasma serotonin concentration was measured by HPLC, and tryptamine (TRP), tyramine (TYR), phenylethylamine (PEA), and isoamylamine (IAA) were measured by liquid chromatography-mass spectrometry., Results: 15 amines were identified in cecal contents. Plasma TRP, TYR, PEA, and IAA concentrations ranged from 10pM to 100nM in both groups of ponies. Plasma concentrations of serotonin or other amines did not differ between clinically normal ponies and those predisposed to laminitis; however, significantly higher concentrations of TRP, PEA, and IAA were found in samples obtained in the spring, compared with winter samples., Conclusions and Clinical Relevance: Various amines are found in the cecum of ponies, several of which can be detected in the plasma. Concentrations increase significantly in the spring and may reach concentrations close to the threshold for causing vasoconstriction. Release of amines from the cecum into the systemic circulation may contribute to hemodynamic disturbances in horses and ponies with acute laminitis.

Rasagiline [N-propargyl-1R(+)-aminoindan; TVP1012] is a potent irreversible monoamine oxidase (MAO) inhibitor with selectivity for type B of the enzyme, which is being developed for treatment of Parkinson's disease. In this study we examined effects of rasagiline on CNS monoamine levels, modification of behavioural response to L-tryptophan, fluoxetine and L-DOPA, and reversal of reserpine syndrome. Reserpine-induced ptosis was reversed by rasagiline at doses above 2 mg x kg(-1) i.p., which inhibit MAO-A as well as MAO-B, but not at MAO-B-selective doses. However, combination of rasagiline (10 mg x kg(-1) i.p.) with L-DOPA or L-tryptophan (50 mg x kg(-1) i.p.), or rasagiline (10 mg x kg(-1) p.o.) with fluoxetine (10 mg x kg(-1) p.o.), did not induce the behavioural hyperactivity syndrome which is seen following inhibition of both MAO-A and MAO-B by tranylcypromine together with the monoamine precursors. Following oral administration, levels of noradrenaline (NA), 5-hydroxytryptamine (5-HT) and dopamine (DA) were unaffected in hippocampus and striatum after single doses of rasagiline up to 2 mg x kg(-1). Following chronic oral administration (21 days, one dose daily), levels of NA, 5-HT and DA in hippocampus and striatum were unaffected by rasagiline at doses up to 1 mg x kg(-1). Rasagiline does not modify CNS monoamine tissue levels or monoamine-induced behavioural syndromes at doses which selectively inhibit MAO-B but not MAO-A.

Previous pharmacological studies have implicated serotonergic brain systems in opiate withdrawal. To test the hypothesis that serotonin (5-HT) has a critical role in the development of opiate withdrawal, we have employed a near-total brain 5-HT system lesion technique (90% depletion) using 5,7-dihydroxytryptamine combined with induction of opiate dependence by implantation of morphine pellets or by repeated injections of increasing doses of morphine. The effects of serotonergic neuron lesion were examined on spontaneous opiate withdrawal (changes in circadian locomotor activity) and naloxone-precipitated opiate withdrawal syndrome (the somatic aspect). The antiwithdrawal properties of clonidine, an alpha(2)-adrenoceptor agonist currently used for clinical treatment for the somatic signs of opiate withdrawal, were tested also in the lesioned rats. Our findings show that serotonergic lesions in morphine-dependent rats did not alter either the spontaneous or the naloxone-induced withdrawal syndrome (with exception of jumping behavior). Moreover, clonidine alleviated the naloxone-induced withdrawal syndrome in lesioned as well as in sham-operated morphine-dependent rats. These results demonstrate that 5-HT systems are not directly responsible for the development of the somatic opiate withdrawal syndrome in morphine-dependent rats.

An evolutionarily conserved feature of neural systems is that they can be modified by neuromodulators. These modulatory chemical signals include the biogenic amines, octopamine (OA), serotonin (5-HT) and dopamine (DA). Such modulation effectively broadens the operational range in which specific neural circuits can function adaptively. This report discusses how these amines are themselves modulated; for example, by the steroid hormone 20-hydroxyecdysone (20-E) or by the addition of a second biogenic amine. Such second-order neuromodulation, termed metamodulation, is discussed in the context of two well-studied invertebrate systems: the tobacco hornworm moth Manduca sexta, a model of neurodevelopment and plasticity, and the medicinal leech Hirudo medicinalis, a long-favored preparation used to study neural circuits at the level of identified neurons. A portion of this article reviews our previous research of M. sexta that shows that the 'preadult' rise in 20-E is both necessary and sufficient for the increased levels of octopamine observed in the adult. Such elevated levels likely play an important role in the production and modulation of adult behaviors. The somatic growth of median octopaminergic neurons and the late expression of OA-immunoreactivity by novel lateral neurons are also demonstrated to be dependent on 20-E. New immunocytochemical results of stained dopaminergic neurons in the larval and adult moth brain are provided as well, and the potential influence of 20-E on the developmental expression of this neuromodulator is presented. Turning attention to the leech, data indicate that the actions of OA are dramatically altered when 5-HT is combined with OA in the bath surrounding the isolated nervous system. Although either OA or 5-HT alone induces fictive swimming behavior, a cocktail of these two amines strongly inhibits the generation of swimming. Subsequent removal of such a mixture induces nearly continuous swimming and constitutes the best swim-inducing stimulus encountered to date. To understand better how these nonadditive effects are achieved, new results are discussed that indicate that the leech brain is the target of metamodulation by the two amines. Both the arthropod and annelid systems presented here highlight the multiple levels of metamodulation that can exist in nervous systems, and the diverse ways that a modulator's actions can become altered over short or long time periods., (Copyright 2003 S. Karger AG, Basel)

The Bennett and Xie model of peripheral nerve injury was used to study the effects of aging on the onset and progression of sciatic nerve ligation (SNL)-induced thermal hyperalgesia and tactile-evoked allodynia in young, mature, and aged Fischer 344 FBNF1 male rats (4-6, 14-16, and 24-26 months old, respectively). A plantar analgesia meter and calibrated von Frey pressure filaments were employed as the analgesiometric assays. In the absence of nerve injury, aged rats were found to be more sensitive than younger animals to noxious thermal stimuli. Following the SNL surgery, thermal hyperalgesia was observed in all three age groups within 3 days. On post-SNL day 35, the paw-withdrawal latency values of the young and mature animals returned to presurgical baseline levels, while the aged rats continued to exhibit thermal hyperalgesia. Tactile-evoked allodynia was apparent within 3 days following peripheral nerve injury in the oldest cohort, but was delayed in the younger animals. On post-SNL days 0 (control), 3, 21, and 35, young, mature, and aged rats were sacrificed and high-performance liquid chromatography and electrochemical detection (HPLC/ECD) methods were used for neurochemical analyses of spinal serotonin (5-HT), norepinephrine (NE), and 5-hydroxyindoleacetic acid (5-HIAA). Spinal 5-HT and NE levels were not significantly altered by the aging process, nor were they affected by peripheral nerve injury. However, spinal 5-HT turnover from the aged animals was greater than that detected in spinal tissue from the younger counterparts. Differences in spinal 5-HT turnover may contribute to age-related variability in spinal nociceptive processing.

The noradrenaline (NA), dopamine (DA) and serotonin (5HT) reuptake inhibitory potency of deprenyl, the highly selective and irreversible inhibitor of MAO-B, methamphetamine enantiomers, and some other MAO inhibitors (clorgyline, J-508, J-511, J-512, J-516, LK-63, U-1424, 2-HxMP) was compared. In vitro hypothalamic NA reuptake was inhibited by (+)-, and (-)-methamphetamine, (+)- J-508 and (+)-deprenyl (IC50: 0.35, 3.5, 17.0 and 17.8 mumol/l, respectively), and U-1424, J-512, J-516, LK-63 and 2-Hx-MP showed IC50 > 1000 mumol/l. Striatal DA reuptake was inhibited by (+)-, and (-)-methamphetamine, (+)-, and (-)-deprenyl and clorgyline with IC50 of 0.6, 42.0, 24.0, 98.6 and 27.0 mumol/l, respectively, however the other compounds were ineffective. Hippocampal 5HT reuptake was slightly inhibited by clorgyline (IC50 205.0 mumol/l), while the other MAO-inhibitors were devoid of potency. Data suggest that potency and selectivity of MAO inhibition and reuptake inhibition are independent features of the compounds, and metabolism of deprenyl results in increased noradrenaline and dopamine reuptake inhibition.

A review of methodology for separation, detection, and quantitative determination of catecholamines, 5-hydroxytryptamine, and their acidic metabolites in biological tissue and fluids by thin-layer chromatography is presented. Selected procedures, including fluorometric scanning densitometry for catecholamine acetyl derivatives and color scanning densitometry for acids, are described.

Examination of HP 184, [N-n-propyl)-N-(3-fluoro-4-pyridinyl) -1H-3-methylindodel-1-amine hydrochloride], in a variety of tests for serotonergic activity revealed some unique properties of this compound. We report here that 100 microM HP 184 enhanced spontaneous release of [3H]serotonin (5-HT) from rat hippocampal slices. This release was independent of the uptake carrier. In vivo assays confirmed that HP 184 (20 mg/kg, i.p.) lacked significant interactions at the norepinephrine (NE) or 5-HT uptake carrier itself. Notably, HP 184 (15 mg/kg, i.p.) reduced drinking behavior in schedule-induced polydipsic (SIP) rats. We previously reported that some selective 5-HT reuptake inhibitors decrease SIP 30-40% after a 14-21 day treatment. In the current study, HP 184 decreased SIP beginning with the first treatment, and this reduction (30%) was maintained for 28 days. We further investigated HP 184 and serotonin metabolite levels. One hour after i.p. administration of 30 mg/kg HP 184, the ratio of whole brain 5-hydroxyindolacetic acid (5-HIAA) to 5-HT was increased, suggesting serotonergic activation. Under these conditions, the brain:plasma ratio of HP 184 was approximately 2:1, with brain concentrations of 1.6 micrograms/gram. We speculate that the spontaneous release effects of HP 184 may be responsible for the behavioral effects observed.

1. The levels of the main norepinephrine, serotonin, and dopamine metabolite excretion in the urine, MHPG, 5HIAA and HVA respectively, were measured in 84 patients with major depressive disorder, 34 delusional (psychotic) and 50 nondelusional (DSM-III-R criteria). 2. Associations with the 17 items of the HDRS were evaluated using the multiple regression analysis model. In the delusional group, MHPG excretion was positively related to the scores in the items of depressed mood (p = 0.04), middle insomnia (p = 0.008) and genital symptoms (p = 0.001). 5HIAA excretion was negatively associated with late insomnia (p = 0.02), work and interests (p = 0.001) and genital symptoms (p = 0.007). HVA was positively related to agitation (p = 0.043). In the nondelusional group the only association found was between agitation and HVA excretion (p = 0.03).

Unlike rats, but similar to primates, guinea pigs exhibit prolonged function of the corpus luteum and elevated progesterone secretion after ovulation. The gonadotropins, estrogen (E) and progesterone (P) have been examined throughout the guinea pig estrous cycle. However, neither prolactin secretion nor its regulation by steroid hormones has been characterized, perhaps due to the lack of a specific radioimmunoassay. beta-Endorphin (BE), substance P (SP), and serotonin (5-HT) increase prolactin secretion in rats and monkeys. BE and SP neurons in guinea pigs and 5-HT neurons in monkeys contain progestin receptors which could mediate neuroendocrine effects of steroid hormones. Therefore, the effects of E and P on prolactin, BE, SP, and 5-HT and its metabolite 5-HIAA were examined in guinea pigs which were ovariectomized, E treated (28 days), and E+P treated (14 days E+14 days E+P). The rat NB2 lymphoma cell line was used as a bioassay for serum prolactin. BE and SP levels were measured by radioimmunoassay in four hypothalamic areas: the preoptic region (POA), the mediobasal hypothalamus (MBH), the dorsomedial hypothalamus (DMH), and the mamillary bodies (MB). 5-HT and 5-HIAA were measured in the midbrain raphe area by high-pressure liquid chromatography. E alone had little effect on serum prolactin levels, but E+P significantly increased prolactin as compared with ovariectomized controls. The BE levels increased with E treatment and remained elevated with E+P treatment in MBH and POA. The BE content was stimulated in DMH and MB by E+P treatment and not with E alone. The SP content in MBH, DMH, and MB increased in E-treated guinea pigs.(ABSTRACT TRUNCATED AT 250 WORDS)

The selective serotonin (5-HT) agonist 8-hydroxydipropylaminotetralin (8-OH-DPAT) has been extensively used to characterize the physiological, biochemical, and behavioral features of the 5-HT1A receptor. A further characterization of this receptor subtype was conducted with membrane preparations from rat cerebral cortex and hippocampus. The saturation binding isotherms of [3H]8-OH-DPAT (free ligand from 200 pM to 160 nM) revealed high-affinity 5-HT1A receptors (KH = 0.7-0.8 nM) and low-affinity (KL = 22-36 nM) binding sites. The kinetics of [3H]8-OH-DPAT binding were examined at two ligand concentrations, i.e., 1 and 10 nM, and in each case revealed two dissociation rate constants supporting the existence of high- and low-affinity binding sites. When the high-affinity sites were labeled with a 1 nM concentration of [3H]8-OH-DPAT, the competition curves of agonist and antagonist drugs were best fit to a two-site model, indicating the presence of two different 5-HT1A binding sites or, alternatively, two affinity states, tentatively designated as 5-HT1AHIGH and 5-HT1ALOW. However, the low correlation between the affinities of various drugs for these sites indicates the existence of different and independent binding sites. To determine whether 5-HT1A sites are modulated by 5'-guanylylimidodiphosphate, inhibition experiments with 5-HT were performed in the presence or in the absence of 100 microM 5'-guanylylimidodiphosphate. The binding of 1 nM [3H]8-OH-DPAT to the 5-HT1AHIGH site was dramatically (80%) reduced by 5'-guanylylimidodiphosphate; in contrast, the low-affinity site, or 5-HT1ALOW, was seemingly insensitive to the guanine nucleotide. The findings suggest that the high-affinity 5-HT1AHIGH site corresponds to the classic 5-HT1A receptor, whereas the novel 5-HT1ALOW binding site, labeled by 1 nM [3H]8-OH-DPAT and having a micromolar affinity for 5-HT, may not belong to the G protein family of receptors. To further investigate the relationship of 5-HT1A sites and the 5-HT innervation, rats were treated with p-chlorophenylalanine or with the neurotoxin p-chloroamphetamine. The inhibition of 5-HT synthesis by p-chlorophenylalanine did not alter either of the two 5-HT1A sites, but deafferentation by p-chloroamphetamine caused a loss of the low-affinity [3H]8-OH-DPAT binding sites, indicating that these novel binding sites may be located presynaptically on 5-HT fibers and/or nerve terminals.

The authors studied the effect of active immunization of rats with bovine serum albumin and serotonin-bovine serum albumin conjugate on the distribution of biogenic amines in the brain and the behaviour of the animals. It is shown that the effect of the studied antigens on the condition of the brain mediator systems and the animals' behaviour differ in their trend, which must be taken into account in choosing adequate control in studies with induction of antibodies against low-molecular substances by means of conjugated antigens.

The effect of progesterone (P) on serotonin (5-HT) turnover was studied in nine brain regions in ovariectomized rats primed with bilateral intracerebral implants of estradiol benzoate (1:250 cholesterol) directed towards the ventromedial hypothalamus (VMN). Two days after surgery, animals received P (0.5 mg SC), and were pretested for lordosis behavior. After a 44-h recovery period, rats with LQ > or = 60 were randomly divided into groups that received either a second behavior test or IP injections of saline or pargyline (4 h after P or V). P treatment decreased pargyline-induced accumulation of 5-HT in the VMN (pars lateralis), the lateral midbrain central grey (IMCG), and the periventricular region (PVE, anterior hypothalamic region). The 5-HIAA/5-HT ratios were significantly decreased in the VMN and PVE in P-treated animals. These results support the hypothesis that P-influenced decreases in serotonergic activity in the VMN contribute to the facilitation of female receptivity, and also suggest that steroid-mediated actions in the VMN may lead to changes in serotonergic activity in the IMCG and PVE.

Using high-performance liquid chromatography and gas chromatography, we reevaluated the 24-h influence of a serotonin- and dopamine-rich diet on platelet serotonin and serotonin, 5-hydroxyindoleacetic acid (5-HIAA), and major catecholamine metabolites in the urine of 15 healthy adults. Although there were significant responses in urinary free serotonin and catecholamine metabolites, their concentrations did not exceed the upper limits of the reference ranges for any of the participants. For urinary 5-HIAA, pronounced effects were observed within 2-4 h. After 6-8 h, results for 11 participants exceeded the upper limit of the reference range. The median recovery of dietary serotonin as urinary 5-HIAA was 20% and subject to a large range (1-50%). There was no significant change in platelet serotonin. We conclude that, using specific analytical methods, no dietary restrictions need be imposed to diagnose catecholamine (metabolite)-producing tumors. For diagnosis of carcinoids on the basis of urinary 5-HIAA it is appropriate to completely abstain from serotonin-containing foods for greater than or equal to 12 h before testing. Platelet serotonin is a more sensitive marker for carcinoids that produce only small amounts of serotonin, and is unaffected by dietary serotonin.

The aim of the present study was to identify cellular elements bearing high-affinity neurotensin (NT) binding sites in the suprachiasmatic nucleus (SCN) of the rat hypothalamus. Because the distribution of these binding sites had previously been reported to conform to that of both vasoactive intestinal peptide (VIP)-containing nerve cell bodies and serotonin (5-HT)-containing axons, the following experimental approaches were used: (1) the overlap between autoradiographically labeled NT binding sites and immunocytochemically labeled VIP neurons was examined in adjacent 5-microns-thick sections taken across the entire rostrocaudal extent of the SCN; and (2) the density of NT binding sites was examined by quantitative autoradiography following cytotoxic lesioning of 5-HT afferents. Double-labeling studies demonstrated precise overlap between 125I-NT binding and VIP immunostaining throughout the SCN. Moreover, at high magnification intensely VIP-immunoreactive neurons were found in direct register with 125I-NT-labeled cells visualized in adjacent sections. Densitometric autoradiographic studies demonstrated a significant reduction in specific 125I-NT binding within the SCN following intracerebroventricular injection of the neurotoxin, 5,7-dihydroxytryptamine. Taken together, these results indicate that within the SCN, NT receptors are present both presynaptically on serotonin axons and postsynaptically on the perikarya and dendrites of VIP-containing neurons.

Administration of non-competitive N-methyl-D-aspartate (NMDA) antagonists in rodents leads to a characteristic motor syndrome which has been related to changes in monoamine metabolism in a variety of brain regions. We examined the question whether chronic MK-801 treatment in neonatal rats from postnatal day 8 through 19, which has been shown previously to alter NMDA receptor function, would also affect monoamine metabolism in striatum and frontal cortex of adult rats. Monoamines and their metabolites were determined 5 months after the treatment using high-performance liquid chromatography with electrochemical detection. Dihydroxyphenylacetic acid (DOPAC) concentration was elevated (greater than 40%) in both regions tested, while 5-hydroxyindoleacetic acid (5-HIAA) concentration was significantly elevated only in the cortex (19%), and 3-methoxy-4-hydroxyphenylglycol (MHPG) only in the striatum (47%). These results demonstrate that the long-lasting effects of chronic neonatal MK-801 treatment are not restricted to glutamate transmission, but include monoamine transmission as well.

Destruction of nigrostriatal dopamine (DA) neurons with 6-hydroxydopamine (6-OHDA) early in development results in hyperinnervation of striatum by the serotonergic afferents deriving from the dorsal raphe nucleus. We have used in vivo microdialysis to investigate the degree to which serotonergic neurotransmission in striatum is altered by this increase in the density of serotonin (5-HT) terminals. The effects of several manipulations known to influence 5-HT function on extracellular 5-HT and 5-hydroxyindoleacetic acid in striatum were compared in adult rats treated neonatally with 6-OHDA and in intact adult rats. Basal levels of 5-HT in extracellular fluid (ECF) of striatum were similar in neonatally DA-depleted rats and in intact rats. Perfusion with the 5-HT reuptake blocker, fluoxetine (100 microM), increased 5-HT in striatal ECF of neonatally DA-depleted rats to levels that were threefold greater than those achieved in intact rats. Likewise, K(+)-depolarization of the 5-HT terminals (100 mM in perfusate) or systemic administration of the 5-HT releaser, (+/-)-fenfluramine (10 mg/kg i.p.), increased the concentration of 5-HT in striatal ECF of neonatally DA-depleted rats to levels approximately threefold greater than those observed in striatum of intact rats. These findings indicate that the 5-HT hyperinnervation of striatum that takes place in rats depleted of DA at infancy is associated with an increased capacity for neurotransmitter release in this system. Concomitant increased in high-affinity 5-HT uptake may prevent the occurrence of any measurable changes in the resting concentration of 5-HT in striatal ECF.

The transmitter mechanism of a long-lasting descending inhibition of the monosynaptic reflex was investigated in the isolated spinal cord of the neonatal rat. The monosynaptic reflex elicited by dorsal root stimulation was recorded extracellularly from a lumbar ventral root (L3-L5). Electrical stimulation of the upper thoracic part of the hemisected cord caused an inhibition lasting about 40 s of the monosynaptic reflex. This descending inhibition was markedly attenuated by perfusing the spinal cord with reserpine (1 microM) or 5,7-dihydroxytryptamine (10 microM) for 2-6 h. The perfusion with reserpine (1 microM) for 4 h significantly decreased the contents of 5-hydroxytryptamine, dopamine, and norepinephrine of the neonatal rat spinal cord, whereas the perfusion with 5,7-dihydroxytryptamine (10 microM) for 4 h decreased the contents of 5-hydroxytryptamine and dopamine. The descending inhibition was markedly potentiated by a 5-hydroxytryptamine uptake blocker, citalopram (10 nM), and was blocked by a 5-hydroxytryptamine antagonist, ketanserin (10-100 nM). Application of 5-hydroxytryptamine to the spinal cord induced an inhibition of the monosynaptic reflex, a later part of which was blocked by ketanserin. Ketanserin also moderately blocked inhibitions of the monosynaptic reflex caused by norepinephrine and dopamine. Phentolamine (10 microM) abolished the depressant actions of norepinephrine and dopamine, but did not affect that of 5-hydroxytryptamine or the descending inhibition. These results strongly suggest the involvement of 5-hydroxytryptamine, but not dopamine nor norepinephrine, in the descending inhibition. Besides ketanserin, the descending inhibition was blocked by ritanserin, haloperidol, and pipamperone, which have affinities to 5-hydroxytryptamine2 receptors, and also by spiperone and methiothepin, which are antagonists at both 5-hydroxytryptamine1 and 5-hydroxytryptamine2 receptors (all 1 microM). On the other hand, a 5-hydroxytryptamine1C and 5-hydroxytryptamine2 antagonist, mesulergine (1 microM), and 5-hydroxytryptamine3 antagonists, ICS 205-930 and quipazine (both 1 microM), did not depress either the descending inhibition or the 5-hydroxytryptamine-evoked inhibition of the monosynaptic reflex. The results with these antagonists favor the involvement of 5-hydroxytryptamine2 receptors although the results with mesulergine disagree with this notion. 5-Hydroxytryptamine1 agonists, such as 8-hydroxy-2-(di-n-propylamino)tetralin, buspirone, and 5-carboxyamidotryptamine, and a 5-hydroxytryptamine3 agonist, 2-methyl-5-hydroxytryptamine, induced a long-lasting inhibition of the monosynaptic reflex, which was blocked by ketanserin whereas a 5-hydroxytryptamine2 agonist, S-(+)-alpha-methyl-5-hydroxytryptamine, evoked a biphasic inhibition, in which only the later component was blocked by ketanserin.(ABSTRACT TRUNCATED AT 400 WORDS)

The sodium-ion coupled transporters for 5-hydroxytryptamine (5HT), noradrenaline and dopamine function to reduce extracellular levels of biogenic amines. Over the past fifteen years selective inhibitors of these transport systems have been developed including fluoxetine, citalopram, paroxetine, litoxetine (for 5HT), nisoxetine, desipramine, maprotiline (for noradrenaline) and GBR-12935 (for dopamine). Some of these inhibitors, including drugs selective for noradrenaline transport and particularly those selective for the 5HT transport system are currently widely used in the clinical management of affective disorders. Selective biogenic amine uptake inhibitors have, in addition, provided tools to undertake molecular pharmacological and biochemical studies of their respective transporters. By this means, the rat brain 5HT and dopamine transporters have been identified as polypeptides with relative molecular masses of 73,000 and 80,000, respectively, using affinity-chromatographic purification and photoaffinity-labelling techniques. Recently, the biogenic amine transporters have been cloned and a comparison of their predicted amino acid sequences reveals that these proteins share a considerable degree of similarity with notably 12-13 transmembrane spanning domains. Perspectives for future fundamental and clinical research on biogenic amine transport systems using molecular biological techniques are discussed.

The studies reviewed here represent a continuing search for mechanisms which play a role in neurological disturbances resulting from brain injury. Focal cortical freezing lesions in rats were shown to cause a widespread decrease in local cerebral glucose utilization (LCGU) in cortical areas of the lesioned hemisphere and this was interpreted as reflecting a depression of cortical activity. Such an interpretation was supported by the finding that in lesioned brain reduction of cerebral metabolism by pentobarbital and isoflurane was limited by the metabolic depression that has already occurred as a result of injury and by the demonstration that the energy status and substrate (glucose) supply in the cortical areas in the injured brain have not been compromised at the time when LCGU was decreased. Both the serotonergic and the noradrenergic neurotransmitter systems were implicated in functional alterations associated with injury. Cortical serotonin (5-HT) metabolism was increased throughout the lesioned hemisphere and complete inhibition of 5-HT synthesis with p-chlorophenylalanine ameliorated the decrease in cortical LCGU, interpreted as reflecting cortical functional depression. Cortical norepinephrine metabolism was bilaterally increased in focally injured brain, while prazosin, a selective alpha 1-noradrenergic receptor blocker, normalized cortical LCGU in the lesioned hemisphere. Low-affinity in vivo binding of [125I]HEAT, another selective alpha 1-receptor ligand, was specifically increased in cortical areas of the lesioned hemisphere at the time of the greatest depression in LCGU, suggesting that alpha 1-adrenoreceptors may be of functional importance in injured brain.(ABSTRACT TRUNCATED AT 250 WORDS)

To determine if reported reductions of regional cerebral metabolic rates for glucose (rCMRglc) induced by the 5-HT agent metachlorophenylpiperazine (MCPP) (2.5 mg/kg) are due to a presynaptic action, 3-month old Fischer-344 rats were given parachloroamphetamine (PCA), a serotonin neurotoxin, and rCMRglc was measured 1 or 3 weeks later with the quantitative autoradiographic [14C]2-deoxyglucose procedure in 74 brain regions after administering saline, MCPP or other drugs. PCA alone increased rCMRglc significantly only in the raphe nuclei and in visual structures (visual cortex, lateral geniculate, superior colliculus). MCPP alone reduced rCMRglc in 75% of the regions studied. In PCA-lesioned rats, metabolic responses to MCPP 2.5 mg/kg were virtually abolished and rCMRglc was increased in interanteromedial and centrolateral thalamic nuclei. rCMRglc responses to quipazine, a postsynaptic serotonin agonist, and to arecoline and bromocriptine, cholinergic and dopaminergic agonists, were unchanged by PCA-pretreatment. Selective abolition by PCA of the metabolic response to MCPP confirms that MCPP, at the dose studied, reduces rCMRglc in the forebrain via a presynaptic mechanism and that postsynaptic serotonergic function is not altered by PCA.

To clarify the pharmacological mechanism by which ceruletide affects involuntary movements, we used 20-h food-deprived mice to examine the acute effects of ceruletide (600 micrograms/kg, i.p.) on the histochemistry of striatal dopaminergic and serotonergic systems. The latter was unchanged but a reduction in catecholamine fluorescence was seen which was restricted to the ventrolateral (VL) portion of the striatum. Biochemical assays also indicated decreased levels of dopamine (DA) and its metabolites in this restricted region of the striatum with little or no change in noradrenaline, serotonin or their metabolites. In all regions examined, except the dorsomedial part of the mid-striatum, the ratio of dopamine metabolites to dopamine was higher in the ceruletide-treated group than in controls, suggesting increased DA release. Further pharmacological experiments showed that, compared to results in mice receiving only ceruletide: the ceruletide-induced decreases in DA and dihydroxyphenylacetic acid (DOPAC) in VL were less after alpha-methyl-p-tyrosine treatment; ceruletide caused no significant decrease in either DA or DOPAC after pargyline pretreatment, although the low levels of homovanillic acid (HVA) were still further significantly reduced; and the ceruletide-induced decrease of DA was reduced, that of DOPAC was abolished and that of HVA enhanced by nomifensine pretreatment. These results suggested that ceruletide might induce a more rapid degradation of DA in VL and increased efflux of HVA through the blood-brain barrier. This evidence suggests that ceruletide has a regionally specific effect on the striatal dopaminergic system which may relate to the amelioration of involuntary movements.

The present study was undertaken to determine cerebrospinal fluid (CSF) and brain levels of norepinephrine (NE), serotonin (5-HT) and their metabolites--3,4-dihydroxyphenylacetic acid (DOPAC), 4-hydroxy-3-methoxyphenylacetic acid (HVA) and 5-hydroxyindole-3-acetic acid (5-HIAA)--in rats pretreated with 6-hydroxydopamine (6-OHDA) or 5,7-dihydroxytryptamine (5,7-DHT). In the 6-OHDA pretreated rats, both CSF and brain concentrations of NE, DOPAC and HVA sustained significant decreases as compared with those in non-treated rats. Positive and significant correlations between CSF and brain levels were observed in respect to NE, DOPAC and HVA. In 5,7-DHT pretreated rats, both CSF and brain concentrations of 5-HT and 5-HIAA were significantly decreased. A positive and significant correlation between CSF and brain levels in respect to 5-HT and 5-HIAA was observed. Further studies were carried out to determine ACh levels of both the CSF and the brain in microspheres (MS)-treated rats, which are used as a model of microembolization. The CSF ACh concentrations in MS-treated groups were significantly decreased as compared with those in non-treated rats. The brain ACh contents also tended to decrease in this group. A positive and significant correlation was observed between CSF and brain levels of ACh. These findings suggest that NE, 5-HT and ACh concentrations in the CSF are direct indications of central noradrenergic, serotonergic and cholinergic nerve activity, respectively.

The effect of a low single dose of lindane (gamma-hexachlorocyclohexane) on monoaminergic neurotransmission during brain postnatal development was studied in 8-, 15-, 22- and 29-day-old suckling rats. Concentrations of noradrenaline, serotonin, dopamine and their metabolites were determined in eight cerebral regions 1 h after dosing (20 mg/kg lindane per os). All these aminergic systems were altered in a regional- and age-related pattern. Decreases of noradrenaline in regions rich with noradrenergic terminals together with increases of the ratio 5-HIAA/serotonin and DOPAC/dopamine suggest, as a whole, an enhanced release of the monoamines. This increased neuronal activity does not exclude an initial action of lindane on the inhibitory GABAergic system that would activate the neurotransmitter release in other systems shortly after a single administration of the neurotoxic agent.

Derivatives of amphetamine are potent releasers of both dopamine (DA) and serotonin (5-HT), but the relative contributions of DA and 5-HT release to the behavioral effects of these drugs have not been established. Previously, S-(+)3,4-methylenedioxymethamphetamine (S-(+)MDMA) was found to produce locomotor hyperactivity in rats which was dependent on 5-HT release. The present study found that MBDB (1.25, 2.5, 5.0 or 10.0 mg/kg), the alpha-ethyl derivative of MDMA that produces little or no direct DA release, also induced locomotor hyperactivity that lasted for greater than 60 min after the 5.0 and 10.0 mg/kg doses. MBDB produced spatial patterns of locomotor hyperactivity and suppression of exploratory activity (holepokes and rearings) very similar to the behavioral syndrome produced by MDMA. MBDB-induced hyperactivity was blocked by pretreatment with the selective 5-HT uptake inhibitor fluoxetine (2.5 or 10 mg/kg), suggesting that MBDB produced behavioral effects via uptake-carrier mediated release of 5-HT. Similarly, fluoxetine pretreatment blocked the locomotor hyperactivity produced by S-(+)3,4-methylenedioxyamphetamine (3.0 mg/kg) or p-chloroamphetamine (2.5 mg/kg), supporting a serotonergic basis for the action of these drugs. Tissue levels of 5-HT and its metabolite 5-HIAA were decreased 40 min after administration of S-(+)MDMA (3.0 mg/kg) or MBDB (5.0 mg/kg), and these decreases were prevented by fluoxetine pretreatment. S-(+)MDMA also produced a fluoxetine-sensitive increase of tissue DA levels, suggesting that 5-HT release may indirectly result in increased DA release, although MBDB did not significantly increase DA levels.(ABSTRACT TRUNCATED AT 250 WORDS)

The purpose of the present experiment was to determine the effects of lesions of cholinergic neurons originating from the nucleus basalis magnocellularis (NBM), alone or in combination with central serotonin depletion, on learning and memory in rats trained in the Stone 14-unit T-maze--a complex, positively-reinforced spatial discrimination task. Lesion of cholinergic neurons within the NBM was accomplished by bilateral infusion of ibotenic acid. Serotonin depletion was accomplished by the systemic administration of p-chloroamphetamine (PCA). The results show that PCA-induced serotonin depletion enhanced learning. This effect was completely prevented by NBM lesions, despite the fact that NBM lesions alone did not affect the performance of rats in this task. The results of this study support the view that the cholinergic and serotonergic systems may functionally interact in learning and memory processes. The significance of this interaction in the etiology and treatment of dementia should be further investigated.

Inasmuch as sustained treatment with the 5-hydroxytryptamine1A (5-HT1A) agonist, ipsapirone, is necessary for inducing anxiolytic and antidepressant effects in the clinic, investigations were performed for assessing the possible changes in serotoninergic and dopaminergic neurotransmission in the brain of rats 24 hr after a 2-week treatment with this drug. Receptor binding assays with membranes and quantiative autoradiography indicated that the twice-daily administration of ipsapirone (5 mg/kg i.p.) for 14 days did not alter the characteristics of 5-HT1A sites in the hippocampus, septum and dorsal raphe nucleus. In contrast, significant decreases in the Bmax values for 5-HT2 sites (-24%) and 5-HT3 sites (-19%) were found in the frontal and posterior cortex, respectively. As expected from unchanged postsynaptic 5-HT1A receptors, inhibition of forskolin-stimulated adenylate cyclase by 5-HT1A agonists (8-hydroxy-2-(di-n-propylamino)tetralin, ipsapirone) exhibited the same characteristics in hippocampal homogenates from both control and ipsapirone-treated animals. An acute administration of 8-hydroxy-2-(di-n-propylamino)tetralin (0.5 mg/kg i.p.) or ipsapirone (1 or 5 mg/kg i.p.) 24 hr after the last injection for the chronic treatment produced a similar decrease in the rate of 5-HT turnover in various brain areas in rats treated for 2 weeks with saline or ipsapirone. At the highest dose (5 mg/kg i.p.), acute ipsapirone also increased the rate of dopamine turnover in the striatum and cerebral cortex approximately to the same extent in both treatment groups. In vitro recording of the firing of serotoninergic neurons in brain stem slices revealed a desensitization of the somatodendritic 5-HT1A receptors, which might be responsible for the increased 5-HT turnover in the brain stem and striatum of rats chronically treated with ipsapirone as compared with controls. These data demonstrated that chronically administered ipsapirone produces adaptive changes in central serotoninergic neurotransmission which might account for the anxiolytic and antidepressant properties of this drug after sustained treatment.

The concentrations of noradrenaline (NA), dopamine (DA), serotonin (5-HT), and their metabolites were determined in 5 brain areas of non-pregnant, 15 and 20 day pregnant and 4 day post-partum rats. Striatal 5-HT content was significantly lower in 15 and 20 day pregnant rats than in estrous controls. A significant decrease in striatal and frontal cortex 5-hydroxyindole-3-acetic acid (5-HIAA) concentration was observed in 15 day pregnant rats. Significant increases in hypothalamic and hippocampal NA levels were observed at 4 days post-partum. Frontal cortex serotonin S2 receptor KD was reduced in 4 day post-partum rats. There was no significant change in S2 receptor Bmax during pregnancy. Levels of progesterone were negatively correlated with striatal DA, homovanillic acid (HVA), 5-HT, and 5-HIAA levels, hypothalamic DA, hippocampal 5-HT, and frontal cortex 5-HIAA values as well as striatal HVA to DA, and HVA to 3,4-dihydroxyphenylacetic acid (DOPAC) ratios and amygdaloid HVA to DOPAC ratios. The limbic neurotransmitter changes might possibly contribute to mood changes which occur during pregnancy and post-partum.

Despite the fact that mast cells isolated from rat mesentery and lung tissue contain 5-HT in excess of histamine, the pattern of amine output, in response to compound 48/80, mirrors that in peritoneal mast cells where histamine is in excess of 5-HT, such that this secretagogue induces a greater percentage release of histamine than 5-HT. Mast cells are capable of taking up both these amines, although uptake of 5-HT is in preference to that of histamine. With concentrations of clomipramine and fluoxetine that inhibited 5-HT uptake, the net percentage release of 5-HT increased in a corresponding manner, and the concentration-effect curves in response to compound 48/80 ran in a collinear fashion with that of control histamine output (measured in the absence of the drugs). Both drugs had no effect upon the uptake or secretion of histamine. Thus, observed differences in the apparent pattern of histamine and 5-HT secretion from rat mast cells may be due to selective reuptake of amines rather than a reflection of differential amine release.

8-Hydroxy-(di-n-propylamino)tetralin (8-OH-DPAT) has antidepressant-like effects in rats and selectively reduces presynaptic 5-HT1A function a day after administration. In the present study, the effect of 8-OH-DPAT (1 mg/kg s.c.) pretreatment on presynaptic (raphe nuclei) and postsynaptic (frontal cortex and hippocampus) [3H]8-OH-DPAT binding was studied. Bmax values were markedly reduced in the raphe, but not in the hippocampus and frontal cortex. Kd values were unchanged. Electrical stimulation of the dorsal raphe (300 microA, 1 ms, 20 Hz, 30 min) significantly increased 5-hydroxyindoleacetic acid in the frontal cortex, but not in the amygdala or the nucleus accumbens and caused smaller increases in the rest of the brain. The increase in the frontal cortex was significantly potentiated one day after giving 8-OH-DPAT. These results confirm the ability of 8-OH-DPAT to desensitise presynaptic 5-HT1A receptors and suggest that this may lead to a loss of feedback control so that, on neuronal stimulation, the increase of 5-HT function is enhanced. This effect may underlie the antidepressant-like action of 8-OH-DPAT pretreatment, i.e. its ability to oppose restraint-induced defects in locomotion on placement in an open field one day later. A requirement of presynaptic 5-HT for this behavioural effect is consistent with its prevention by the 5-HT synthesis inhibitor parachlorophenylalanine.

The amine transporter from bovine chromaffin granules has been purified in a functional state. Two isoforms with different pI values have been separated and shown to be active. One with an unusually acidic pI (approximately 3.5) has been shown to be a glycoprotein with an apparent Mr of 80,000. The purified polypeptide catalyzes transport of serotonin upon reconstitution with an apparent Km of 2 microM and a Vmax of 140 nmol/mg/min, 150-200-fold higher than the one determined in the native system. Transport is inhibited by reserpine and tetrabenazine, ligands which bind to two distinct sites on the transporter. These findings suggest that the binding sites for both drugs reside on a single polypeptide. The reconstituted purified transporter binds [3H]reserpine with a biphasic kinetic behavior, KD values of 0.3 and 30 nM and Bmax of 310 and 4200 pmol/mg protein, respectively. In addition, binding of [3H]reserpine is accelerated upon imposition of a pH gradient across the proteoliposome. From these findings it is evident that a single polypeptide catalyzes the various functions of the transporter.

The influence of induction of antibodies to the neuromediator serotonin in the case of active immunization of animals with a conjugate serotonin-protein antigen on the distribution of biogenic amines in the brain and on behavioral responses was investigated in experiments on rats. It was shown that active immunization of rats with a serotonin-protein conjugate leads to a decrease in serotonin, its metabolite 5-hydroxyindole-3-acetic acid, as well as dopamine in certain brain structures. Against a background of induction of antibodies to serotonin, the horizontal motor activity of the animals is decreased.

1. Central 5-HT is thought to be involved in neuronal inhibition and as such as a modulating influence in restraining the organism from responding to (e.g., especially adverse) stimuli. 2. Evidence for a role of central 5-HT in suicide arises from reduced concentrations of brain 5-HT or 5-HIAA in brain stem, reduced binding of [3-H]-IMI in brain tissue of frontal cortex/hypothalamus, and increased binding of radioligands to 5-HT-2 receptors in the frontal cortex. 3. Evidence for a role of central 5-HT in parasuicide arises from reduced concentrations of lumbar CSF 5-HIAA, reduced PRL responses to d,l-fenfluramine challenge, and increased CORT responses to 5-HTP challenge. 4. Since reduced central 5-HT activity appears to be consistently associated with impulsive aggression, it is possible that suicidal and parasuicidal acts in individuals with evidence of reduced central 5-HT activity are a manifestation of reduced impulse control. 5. Agents which enhance central 5-HT function and/or diminish the activity of neuronal systems involved in arousal (e.g. norepinephrine or dopamine) should be efficacious in reducing parasuicidal behavior.

1. Psychotropic drugs ameliorate psychotic symptoms only after repeated administration. 2. To assess the neurochemical effects of chronic haloperidol and lithium administration, microdialysis was performed simultaneously in the prefrontal cortex, the nucleus accumbens, and the striatum after haloperidol, and separately in the lateral hypothalamus and the hippocampus after lithium. 3. Chronic administration of haloperidol decreased dopamine turnover in the prefrontal cortex and the striatum. It did not affect the nucleus accumbens detectably. 4. No tolerance to haloperidol developed in any of the three regions. 5. Lithium enhanced the response of the serotonergic system to amphetamine in the lateral hypothalamus but not in the hippocampus. 6. The antipsychotic effect of haloperidol might be related to dopamine turnover decrease in the prefrontal cortex. 7. The antidepressant effect of lithium might be related to enhancement of serotonin responsiveness in the hypothalamus.

The acute and chronic effects of the "serotonergic anorectics" quipazine and dl-fenfluramine were examined in rats with substantial and specific depletions of brain 5-hydroxytryptamine (5-HT) induced by 5,7-dihydroxytryptamine (5,7-DHT). A "dessert" test which did not involve food deprivation was used to assess anorexia. Markedly increased sensitivity to the L-5-HTP-induced behavioral syndrome in 5,7-DHT-lesioned rats indicated postsynaptic 5-HT receptor supersensitivity. We found low (2 mg/kg) and intermediate (5 mg/kg) doses of fenfluramine, a putative presynaptic agent, were more effective in producing anorexia in lesion rats versus controls. A higher dose of fenfluramine (10 mg/kg) was less effective in lesion rats, suggesting that high dose and low dose fenfluramine anorexia are mediated by different mechanisms. We found quipazine, a putative 5-HT postsynaptic agonist, in a dose range of 2-10 mg/kg, to be no more effective in producing anorexia in lesion rats compared to controls. The development of tolerance to both fenfluramine and quipazine anorexia was similar for lesion and control rats showing that an intact brain 5-HT system is not necessary for tolerance. Tolerance to the "behavioral syndrome" induced by high doses of these agents developed rapidly in controls but not at all in lesion rats. This suggests that the behavioral syndrome and anorexia are independent effects of fenfluramine and quipazine. These results also challenge the popular notion that the primary anorectic action of fenfluramine is via brain serotonin.

The effect of ammonia infusion on monoamine metabolism was studied in the rat brain. Seven days after portocaval shunt (PCS) or sham operation animals were infused with ammonia or saline. Brain metabolism of serotonin and norepinephrine was studied after injection of a decarboxylase inhibitor (m-hydroxybenzylhydrazine, NSD 1015) which blocks the conversion of 5-hydroxytryptophan to serotonin and dihydroxyphenylalanine to dopamine. Neurologic testing was conducted before killing. Plasma and brain amino acids were measured. PCS animals infused with ammonia were in deep coma after 6 h infusion, whereas sham-operated animals were virtually unaffected. Brain amino acid analyses demonstrated increased concentrations of the aromatic amino acids and a tenfold increase in glutamine. Serotonin metabolism was diminished after 6 h. Dopamine synthesis was normal, but norepinephrine levels were low after 6h. The study suggests that hyperammonemia in PCS rats results in a depression of the serotonin synthesis rate in accordance with two previous studies but in contrast to previous hypotheses on the regulation of serotonin metabolism.