The discovery and development of buspirone: a new approach to the treatment of anxiety

The Difficult Path to the Discovery of Novel Treatments in Psychiatric Disorders

CNS diseases, including psychiatric disorders, represent a significant opportunity for the discovery and development of new drugs and therapeutic treatments with the potential to have a significant impact on human health. CNS diseases, however, present particular challenges to therapeutic discovery efforts, and psychiatric diseases/disorders may be among the most difficult. With specific exceptions such as psychostimulants for ADHD, a large number of psychiatric patients are resistant to existing treatments. In addition, clinicians have no way of knowing which psychiatric patients will respond to which drugs. By definition, psychiatric diagnoses are syndromal in nature; determinations of efficacy are often self-reported, and drug discovery is largely model-based. While such models of psychiatric disease are amenable to screening for new drugs, whether cellular or whole-animal based, they have only modest face validity and, more importantly, predictive validity. Multiple academic, pharmaceutical industry, and government agencies are dedicated to the translation of new findings about the neurobiology of major psychiatric disorders into the discovery and advancement of novel therapies. The collaboration of these agencies provide a pathway for developing new therapeutics. These efforts will be greatly helped by recent advances in understanding the genetic bases of psychiatric disorders, the ongoing search for diagnostic and therapy-responsive biomarkers, and the validation of new animal models.

Further disentangling the motivational processes underlying benzodiazepine hyperphagia

In addition to their well-known anxiolytic functions, benzodiazepines produce hyperphagia. Previously, we reported that the benzodiazepine, chlordiazepoxide (CDP), increased consumption of both normally-preferred and normally-avoided taste stimuli during long-term (1 h) tests, primarily through changes in licking microstructure patterns associated with hedonic taste evaluation, whereas there was little effect on licking microstructure measures associated with post-ingestive feedback. In this study, we further examined the hedonic and motivational specificity of CDP effects on ingestive behavior. We tested brief access (15 s) licking responses for tastants spanning all taste qualities after treatment with either CDP (5 or 10 mg/kg) or the non-benzodiazepine anxiolytic, buspirone (1.5 or 3 mg/kg). A between-subjects, counterbalanced design compared the CDP or buspirone effects on licking responses for water and a range of weak to strong concentrations of NaCl, Q-HCl, citric acid, MSG, saccharin, and capsaicin under water-restricted (23 h) conditions; and sucrose, saccharin, and MSG under water-replete conditions. In a dose dependent manner, CDP increased licking for taste stimuli that were normally-avoided after saline treatment, with a notable exception observed for the trigeminal stimulus, capsaicin, which was not affected at any concentration or drug dose, suggesting a taste-specific effect of CDP on orosensory processing. Under water-replete conditions, CDP dose-dependently increased licking to normally-accepted concentrations of sucrose, saccharin, and MSG. There was no effect of either drug on licks for water under either water-restricted or water-replete conditions. Buspirone slowed oromotor coordination by increasing brief interlick intervals, but it did not affect licking for any concentrations of the tastants. Overall, these results indicate that benzodiazepines selectively enhance the hedonic acceptance of gustatory orosensory stimuli, independent of general anxiolytic or oromotor coordination effects, or physiological states such as thirst.

Inhibition of SARS-CoV-2 main protease 3CLpro by means of α-ketoamide and pyridone-containing pharmaceuticals using in silico molecular docking

The coronavirus disease infections (COVID-19) caused by a new type of coronavirus (SARS-CoV-2) have been emerging in the entire world. Therefore, it is necessary to find out potential therapeutic pharmaceuticals for this disease. This study investigates the inhibitory effect of the 3-chymotrypsin-like protease of SARS-CoV-2 (3CLpro) using pharmaceuticals containing α-ketoamide group and pyridone ring based on molecular docking. Of these, eight pharmaceuticals approved by US-Food and Drug Administration have shown good contact with the catalytic residues of 3CLpro. They are telaprevir, temsirolimus, pimecrolimus, aminoglutethimide, apixaban, buspirone, lenalidomide, and pomalidomide. Their binding affinity score ranged from -5.6 to -7.4 kcal/mol. Hydrogen bonds were observed and reported. To the knowledge, this study report for the first time a compound that could be binding to ALA285, the new residue resulting from genetic modification of 3CLpro of SARS-CoV-2 that has increased its catalytic activity 3.6-fold compared with its predecessor 3CLpro of SARS-CoV. It is recommended that telaprevir, and pyridone-containing pharmaceuticals including aminoglutethimide, apixaban, buspirone, lenalidomide, and pomalidomide be repurposed for COVID-19 treatment after suitable validation and clinical trials.

The BDNF Val66Met polymorphism (rs6265) enhances dopamine neuron graft efficacy and side-effect liability in rs6265 knock-in rats

Prevalent in approximately 20% of the worldwide human population, the rs6265 (also called ‘Val66Met’) single nucleotide polymorphism (SNP) in the gene for brain-derived neurotrophic factor (BDNF) is a common genetic variant that can alter therapeutic responses in individuals with Parkinson’s disease (PD). Possession of the variant Met allele results in decreased activity-dependent release of BDNF. Given the resurgent worldwide interest in neural transplantation for PD and the biological relevance of BDNF, the current studies examined the effects of the rs6265 SNP on therapeutic efficacy and side-effect development following primary dopamine (DA) neuron transplantation. Considering the significant reduction in BDNF release associated with rs6265, we hypothesized that rs6265-mediated dysfunctional BDNF signaling contributes to the limited clinical benefit observed in a subpopulation of PD patients despite robust survival of grafted DA neurons, and further, that this mutation contributes to the development of aberrant graft-induced dyskinesias (GID). To this end, we generated a CRISPR knock-in rat model of the rs6265 BDNF SNP to examine for the first time the influence of a common genetic polymorphism on graft survival, functional efficacy, and side-effect liability, comparing these parameters between wild-type (Val/Val) rats and those homozygous for the variant Met allele (Met/Met). Counter to our hypothesis, the current research indicates that Met/Met rats show enhanced graft-associated therapeutic efficacy and a paradoxical enhancement of graft-derived neurite outgrowth compared to wild-type rats. However, consistent with our hypothesis, we demonstrate that the rs6265 genotype in the host rat is strongly linked to development of GID, and that this behavioral phenotype is significantly correlated with neurochemical signatures of atypical glutamatergic neurotransmission by grafted DA neurons.

Flow-oriented synthetic design in the continuous preparation of the aryl piperazine drug flibanserin

The first integrated continuous-flow synthesis of the drug substance flibanserin was developed, using an uninterrupted four-step sequence, via an unprecedented route.

Pinoresinol-4,4'-di-O-beta-D-glucoside from Valeriana officinalis root stimulates calcium mobilization and chemotactic migration of mouse embryo fibroblasts

Lignans are major constituents of plant extracts and have important pharmacological effects on mammalian cells. Here we showed that pinoresinol-4,4'-di-O-beta-D-glucoside (PDG) from Valeriana officinalis induced calcium mobilization and cell migration through the activation of lysophosphatidic acid (LPA) receptor subtypes. Stimulation of mouse embryo fibroblast (MEF) cells with 10 microM PDG resulted in strong stimulation of MEF cell migration and the EC(50) was about 2 microM. Pretreatment with pertussis toxin (PTX), an inhibitor of G(i) protein, completely blocked PDG-induced cell migration demonstrating that PDG evokes MEF cell migration through the activation of the G(i)-coupled receptor. Furthermore, pretreatment of MEF cells with Ki16425 (10 microM), which is a selective antagonist for LPA(1) and LPA(3) receptors, completely blocked PDG-induced cell migration. Likewise, PDG strongly induced calcium mobilization, which was also blocked by Ki16425 in a dose-dependent manner. Prior occupation of the LPA receptor with LPA itself completely blocked PDG-induced calcium mobilization. Finally, PDG-induced MEF cell migration was attenuated by pretreatment with a phosphatidylinositol 3-kinase (PI3K) inhibitor such as LY294002. Cells lacking downstream mediator of PI3K such as Akt1 and Akt2 (DKO cells) showed loss of PDG-induced migration. Re-expression of Akt1 (but not Akt2) completely restored PDG-induced DKO cell migration. Given these results, we conclude that PDG is a strong inducer of cell migration. We suggest that the pharmacological action of PDG may occur through the activation of an LPA receptor whereby activation of PI3K/Akt signaling pathway mediates PDG-induced MEF cell migration.

Lactate production and neurotransmitters; evidence from microdialysis studies

Recent studies have found that lactate metabolism plays a significant role in energy supply during acute neural activation in the brain. We will review evidence from microdialysis studies for a relationship between neurotransmitters and lactate production, as revealed in studies of the effects of psychotropic drugs on stress-induced enhancement of extracellular lactate concentrations. Glutamate enhances stress-induced lactate production via activation of N-methyl-D-asparate receptors, and is affected by uptake of glutamate through glutamate transporters. Findings from microdialysis studies suggest that major neurotransmitters, including norepinephrine, dopamine, serotonin, and GABA (via benzodiazepine-receptors) affect lactate production, depending on brain areas, especially during stress. Among these neurotransmitters, glutamate may principally contribute to the regulation of lactate production, with other neurotransmitter systems affecting the extracellular lactate levels in a glutamate-mediated manner. The role for anaerobic metabolism in the supply of energy, as represented by lactate dynamics, deserves further clarification. Monitoring with intracerebral microdialysis is a reliable method for this purpose. Research into this area is likely to provide a novel insight into the mode of action of psychotropic drugs, and the pathophysiology of some of the stress-related mental disorders as well.

Role of 5-HT(1A) receptors in the modulation of stress-induced lactate metabolism in the medial prefrontal cortex and basolateral amygdala

RATIONALE

Lactate has been shown to play a significant role in energy metabolism and reflect neural activity in the brain.

OBJECTIVES

Using in vivo microdialysis technique, we measured extracellular lactate concentrations in the medial prefrontal cortex (mPFC) and the basolateral amygdaloid (BLA) nucleus of rats under electric foot shock stress. Moreover, to examine the role of serotonin (5-HT)(1A) receptors in brain energy metabolism in response to stressors, we attempted to determine whether the stress-induced changes of extracellular lactate levels in the mPFC and BLA are attenuated by tandospirone, a partial agonist at 5-HT(1A) receptors, or perospirone, a novel atypical antipsychotic with a 5-HT(1A) receptor partial agonist and 5-HT(2A)/dopamine-D(2) antagonist property.

RESULTS

Foot shock stress led to an increase in extracellular lactate concentrations both in the mPFC and BLA. Tandospirone (2 mg/kg) attenuated the foot shock stress-induced increase of extracellular lactate concentrations in both of the brain regions, which was blocked by pretreatment with WAY-100635, a selective 5-HT(1A) antagonist. On the other hand, perospirone (0.3 mg/kg) attenuated the increment of extracellular lactate concentrations in the mPFC and BLA, which was unaltered by pretreatment with WAY-100635.

CONCLUSIONS

These results indicate that the foot shock stress-induced increase in lactate metabolism is partly regulated by 5-HT(1A) receptors both in cortical and limbic regions.

Double-blind, comparative study of cyamemazine vs. bromazepam in the benzodiazepine withdrawal syndrome

Cyamemazine is an anxiolytic antipsychotic, which reduces ethanol withdrawal symptoms. Here, we investigated if cyamemazine can be also effective as substitute drug to facilitate benzodiazepine withdrawal. A total of 168 patients treated with benzodiazepines for at least 3 months and with a <18 score in the Hamilton Anxiety Rating Scale (HARS) were included in the study. Previous benzodiazepine treatment was withdrawn, and patients were randomized to a 4-week treatment with cyamemazine (25-50 mg q.d.) or bromazepam (3-6 mg q.d.), followed by 2 weeks of placebo. The primary efficacy variable was the maximal anxiety rebound as measured with the HARS during the 42 days of treatment. No statistically significant differences between treatment groups were found for the extent or incidence of rebound anxiety. Considering all dropout patients as withdrawal failures, after 6 months of follow-up, 56/84 patients in the cyamemazine group (66.7%) and 55/84 patients in the bromazepam group (65.5%) were successfully withdrawn. 28 patients in the cyamemazine group and 18 in the bromazepam group had an adverse event, including anxiety, insomnia, dry mouth and somnolence. No extra-pyramidal symptoms were reported. In conclusion, cyamemazine was comparable to bromazepam in ensuring successful benzodiazepine withdrawal and in controlling the acute benzodiazepine withdrawal syndrome. Cyamemazine may be useful to facilitate benzodiazepine withdrawal in those patients where bromazepam substitution is not appropriate.

Behavioral effects of sinomenine in murine models of anxiety

The present study was designed to investigate the putative anxiolytic-like effect of sinomenine in three experimental models of anxiety in male rats and mice. Use of the elevated plus-maze test revealed that sinomenine (20 and 40 mg/kg, p.o.) increased the percentage of open arm entries and diazepam (2 mg/kg, p.o.) increased the percentage of open arm entries, the percentage of time spent on open arms and total arm entries in mice. In the light/dark transition test, sinomenine (20 and 40 mg/kg, p.o.) increased time spent in the light area and diazepam (2 mg/kg, p.o.) increased time spent in the light area and the overall movements in mice. In the social interaction test, the sinomenine-treated animals significantly increased social interaction time in low light unfamiliar (7 mg/kg, p.o.) and high light unfamiliar conditions (7 and 14 mg/kg, p.o.) as well as diazepam (3 mg/kg, p.o.). Sinomenine (28 mg/kg, p.o.) can also decrease squares entered in rats in social interaction test under low light unfamiliar condition. In the open-field test, sinomenine (160 mg/kg) decreased squares entered in mice. Thus, these findings indicated that sinomenine exhibited anxiolytic-like effect.

Efficacy of buspirone in the treatment of opioid withdrawal

In an attempt to develop a new opiate detoxification approach, the authors assessed the efficacy of buspirone in the treatment of acute heroin withdrawal. Buspirone, a drug interacting with the serotonergic system, was selected because there is evidence that a decrease in serotonergic neurotransmission may be involved in opiate withdrawal symptoms. Twenty-nine hospitalized heroin addicts were randomized to 4 groups: (1) placebo; (2) methadone; (3) buspirone 30 mg daily; (4) buspirone 45 mg daily. The double-blind trial started in all patients with a 5-day methadone stabilization period ending with a 30-mg dose. This was followed from days 6 through 12 by placebo in group 1 and by a methadone taper in group 2. Because of its delayed action, buspirone was started on day 1 in groups 3 and 4 and was continued, after methadone discontinuation, through day 12. On day 13, drugs and placebo were discontinued and patients were observed through day 14. Withdrawal symptoms were assessed with the "Subjective Opiate Withdrawal Scale" (SOWS) and the "Objective Opiate Withdrawal Scale" (OOWS). The SOWS and OOWS scores were significantly higher in the placebo group than in the methadone, buspirone 30 mg, and buspirone 45 mg groups. There were no significant differences in SOWS or OOWS scores when the methadone group was compared with each of the two buspirone groups or when the two buspirone groups were compared with one another. In conclusion, buspirone, a nonopiate drug with no abuse potential, a safe side effect profile and no withdrawal symptoms, at doses of 30 and 45 mg, was as effective as a methadone taper in alleviating the withdrawal symptoms of heroin addicts stabilized for 5 days with, and then withdrawn from, methadone. The use of buspirone could be particularly helpful in outpatient settings where the duration of the methadone taper recommended for detoxification can be lengthy.

Mechanism-Based Pharmacokinetic-Pharmacodynamic Modeling of 5-HT1AReceptor Agonists: Estimation of in Vivo Affinity and Intrinsic Efficacy on Body Temperature in Rats

The pharmacokinetic-pharmacodynamic (PK-PD) correlations of seven prototypical 5-HT(1A) agonists were analyzed on the basis of a recently proposed semi-mechanistic PK-PD model for the effect on body temperature. The resulting concentration-effect relationships were subsequently analyzed on the basis of the operational model of agonism to estimate the operational affinity (pK(A)) and efficacy (log tau) at the 5-HT(1A) receptor in vivo. The values obtained in this manner were compared with estimates of the affinity (pK(i)) and intrinsic efficacy (log[agonist ratio]) in a receptor-binding assay. Between 5-HT(1A) agonists wide differences in in vivo affinity and efficacy were observed, with values of the pK(A) ranging from 5.67 for flesinoxan to 8.63 for WAY-100,635 [N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-2-pyridinyl-cyclohexanecarboxamide] and of the log tau ranging from -1.27 for WAY-100,135 [N-(1,1-dimethylethyl)-4-(2-methoxyphenyl)-alpha-phenyl-1-piperazine-propanamide] to 0.62 for R-(+)-8-hydroxy-2-[di-n-propylamino)tetralin. Poor correlations were observed between the in vivo receptor affinity (pK(A)) and the affinity estimates in the in vitro receptor binding assay (pK(i); r(2) = 0.55, P > 0.05), which could in part be explained by differences in blood-brain distribution. In contrast, a highly significant correlation was observed between the efficacy parameters in vivo (log tau) and in vitro (log [agonist ratio]; r(2) = 0.76, P < 0.05). Thus by combining the previously proposed semi-mechanistic PK-PD model for the effect on body temperature with the operational model of agonism, a full mechanistic PK-PD model for 5-HT(1A) receptor agonists has been obtained, which is highly predictive of the in vivo intrinsic efficacy.

Effect of the serotonin agonist buspirone on behaviour and hypothalamic-pituitary-adrenal axis in confident and fearful mink

Behavioural and hypothalamic-pituitary-adrenal (HPA) axis responses were investigated in farm mink (Mustela vison) selected for either confident or fearful behaviour for nine generations. Two groups of 2-year-old confident (n=12) and fearful (n=12) female mink were given the serotonin (5-HT) 1A receptor agonist buspirone (1.25 mg/kg/day), whereas two other groups of 2-year-old confident (n=12) and fearful (n=12) female mink were given saline, continuously for 5 weeks via osmotic minipumps. Behavioural reactions towards a novel object and towards humans were tested after 19-25 days, and HPA axis reactivity [adrenocorticotropic hormone (ACTH), cortisol] was measured after 28-31 days of treatment. Confident mink were more exploratory than fearful mink towards humans and a novel object. Confident mink spent more time in contact with the object than did fearful mink during saline-but not during buspirone-treatment. buspirone increased approach-withdrawal conflict behaviour towards a object in fearful mink only. The chronic dose of buspirone did not reduce fear towards humans and did not affect latencies to reaction, number of contacts, number and duration of manipulations, and stereotypic behaviour in a Novel Object test. Different HPA axis responses have emerged between confident and fearful mink, together with a different degree of fear-related behaviour. Fearful mink have a higher cortisol combined with a lower ACTH secretion than confident mink in response to capture and blood sampling. The central serotonergic system may be involved, and even though the precise underlying mechanisms are presently unknown, treatment with a 5-HT(1A) receptor agonist reduces the difference between confident and fearful mink in HPA axis reactivity.

Pharmacokinetic-pharmacodynamic modeling of buspirone and its metabolite 1-(2-pyrimidinyl)-piperazine in rats

The objective of this investigation was to compare the in vivo potency and intrinsic activity of buspirone and its metabolite 1-(2-pyrimidinyl)-piperazine (1-PP) in rats by pharmacokinetic-pharmacodynamic modeling. Following intravenous administration of buspirone (5 or 15 mg/kg in 15 min) or 1-PP (10 mg/kg in 15 min), the time course of the concentrations in blood were determined in conjunction with the effect on body temperature. The pharmacokinetics of buspirone and 1-PP were analyzed based on a two-compartment model with metabolite formation. Differences in the pharmacokinetics of buspirone and 1-PP were observed with values for clearance of 13.1 and 8.2 ml/min and for terminal elimination half-life of 25 and 79 min, respectively. At least 26% of the administered dose of buspirone was converted into 1-PP. Complex hypothermic effects versus time profiles were observed, which were successfully analyzed on the basis of a physiological indirect response model with set-point control. Both buspirone and 1-PP behaved as partial agonists relative to R-(+)-8-hydroxy-2-(di-n-propylamino)tetralin (R-8-OH-DPAT) with values of the intrinsic activity of 0.465 and 0.312, respectively. Differences in the potency were observed with values of 17.6 and 304 ng/ml for buspirone and 1-PP, respectively. The results of this analysis show that buspirone and 1-PP behave as partial 5-hydroxytryptamine(1A) agonists in vivo and that following intravenous administration the amount of 1-PP formed is too small to contribute to the hypothermic effect.

Different effects of anxiolytic agents, diazepam and 5-HT(1A) agonist tandospirone, on hippocampal long-term potentiation in vivo

Benzodiazepines and 5-HT(1A) agonists have been widely used as anxiolytic agents. Some clinical reports document that 5-HT(1A) agonists induce memory impairment to a lesser degree than diazepam. In the present study, we compared the effects of diazepam and 5-HT(1A) agonist, tandospirone, on hippocampal long-term potentiation (LTP) in Schaffer collateral-CA1, mossy fiber-CA3 and perforant path-dentate gyrus synapses. In the diazepam-injected group, the reduction in LTP was observed in all three types of synapses, although the effective dose differed among these. In the tandospirone-injected group, no reduction in LTP was observed except in Schaffer-CA1 synapses. In addition, population spike amplitude was potentiated by tandospirone in mossy fiber-CA3 synapses in a dose-dependent manner. Thus, there was a discrepancy in the effects on hippocampal LTP between diazepam and tandospirone, possibly reflecting the reported clinical properties of these drugs, in that 5-HT(1A) partial agonists do not affect learning and memory, whereas diazepam impairs memory function.

Anxiolytic 2,3-benzodiazepines, their specific binding to the basal ganglia

Over the past 20 years, several members of the 2,3-benzodiazepine family have been synthesized. Some of these compounds--tofisopam (Grandaxin), girisopam, nerisopam--exert significant anxiolytic and antipsychotic activities. Sites where actions of 2,3-benzodiazepines are mediated differ from those of 1,4-benzodiazepines. Binding of 2,3-benzodiazepines to neuronal cells in the central nervous system shows a unique and specific distribution pattern: their binding sites are located exclusively to the basal ganglia. Chemical lesioning of the striato-pallido-nigral system, surgical transections of the striato nigral pathway and the activation of c-fos expression in the basal ganglia after application of 2,3-benzodiazepines suggest that these compounds mainly bind to projecting neurons of the striatum. The binding sites are transported from the striatum to the substantia nigra and the entopeduncular nucleus. Recent studies on mechanism of action of 2,3-benzodiazepines indicate their possible role in opioid signal transduction since 2,3-benzodiazepines augment the agonist potency of morphine to induce catalepsy and analgesia, and their action is diminished in morphine tolerant animals. The possible biochemical target of 2,3-benzodiazepines is an alteration in the phosphorylation of protein(s) important in the signal transduction process. Agents affecting emotional responses evoked by endogenous opioids without danger of tolerance and dependence may represent a new therapeutic tool in the treatment of addiction and affective disorders.

Comparative behavioural effects of benzodiazepine and non-benzodiazepine anxiolytics in rhesus monkeys

Quantitative behavioural assessment of benzodiazepines (chlordiazepoxide, diazepam and lorazepam) and non-benzodiazepines (buspirone) anxiolytics were investigated in unrestrained rhesus monkeys (Macaca mulatta) living in social colonies. The different behaviour, categorised as social, solitary and abnormal were video recorded and analysed. Chlordiazepoxide (2.5-5 mg kg-1, p.o.), diazepam (2.5-5 mg kg-1, p.o.) and lorazepam (0.5-1 mg kg-1, p.o.) induced dose-dependent significant changes in certain social and solitary behavioural responses. Thus increases in social grooming, approach, contact, self grooming, feeding and resting with eyes open and decreased aggressiveness and vigilance. On the other hand buspirone (5-10 mg kg-1, p.o.) produced no significant alteration in social and solitary behavioural patterns. On the basis of the above findings the social and solitary behaviour protocol in non-human primates can be a useful tool for studying the effect of a new anxiolytic compound before clinical trial.

A Canadian multicenter study of three fixed doses of controlled-release ipsapirone in outpatients with moderate to severe major depression

Ipsapirone, an azapirone with 5-hydroxytryptamine (5-HT1A) partial agonist activity, has been shown in preliminary studies to be effective in the treatment of major depressive disorder. This 8-week, randomized, double-blind study compared the efficacy, safety, and tolerability of three fixed doses of controlled-release ipsapirone (10-, 30-, and 50-mg dose once daily) with placebo in 410 patients with moderate to severe major depression (Hamilton Rating Scale for Depression [HAM-D] score > or = 20). The 10-mg ipsapirone treatment arm was discontinued early in the study. A total of 390 patients were eligible for evaluation in the intent-to-treat sample. The primary efficacy variable was the change in HAM-D total score from baseline to visit 8. There was no significant difference in efficacy in the two treatment groups versus the placebo group. The overall treatment response, defined as a 50% decrease in the HAM-D total score from baseline, was 43% with ipsapirone 50 mg given once daily, 34% with ipsapirone 30 mg given once daily, and 35% with placebo. In subanalyses, ipsapirone 50 mg given once daily was superior to placebo according to the HAM-D Core Depression (mood, guilt, interest, psychomotor activity) subtotal (p = 0.0453) and Melancholic item (p = 0.0225). Ipsapirone 30 mg given once daily was superior to placebo only in patients with moderate depression (baseline HAM-D total score < or = 25; p = 0.0100). The most common adverse effect in all groups was headache. The only dose-dependent adverse effects were dizziness and nausea.

A primate model of anxiety

Pentylenetetrazol (PTZ; 30 mg/kg, i.m.) produced an acute anxiogenic effect on the behaviour of a social colony of rhesus monkeys acclimatized to laboratory conditions. The animals exhibited hypervigilance, aggressiveness, tachypnea, piloerection and frequent change of posture and also had raised plasma cortisol levels. These effects of PTZ were antagonized by benzodiazepines (diazepam; 1 mg/kg, i.v. and alprazolam; 0.05 mg/kg, p.o.). Non-benzodiazepine anxiolytic drug (buspirone; 10 mg/kg, p.o.) blocked the behavioural effects but not the rise in plasma cortisol concentration. On the other hand, pretreatment with hypnosedative (promethazine; 5 mg/kg, i.m.) or anticonvulsant (sodium valproate; 40 mg/kg, p.o.) agents did not attenuate the effects of PTZ indicating the specificity of its anxiogenic response. The model, thus, seems suitable for evaluation of potential anxiolytic agents.

Effects of chronic diazepam treatment on pre- and postsynaptic 5-HT1A receptors in the rat brain

Biochemical and electrophysiological approaches were used to assess possible changes in 5-HT1A receptors in the rat brain after long-term treatment with an anxiolytic benzodiazepine. Rats were treated with diazepam (2 mg/kg i.p. daily) during 14 days and then untreated for 1 day (protocol A) or 5 days (protocol C) until they were killed for in vitro investigations on 5-HT1A receptors. In addition, other rats (protocol B) received the same 14-day treatment with diazepam, followed by 1 mg/kg of the drug on days 15 and 16, and 0.5 mg/kg on days 17 and 18, and were killed 24 h after the last injection. In vitro binding and quantitative autoradiographic experiments with [3H]8-hydroxy-2-(di-n-propylamino)tetralin ([3H]8-OH-DPAT) showed that the characteristics of 5-HT1A receptor binding sites in the hippocampus and the dorsal raphe nucleus were not significantly altered by the administration of diazepam under the treatment protocols A, B and C. Furthermore, in vitro electrophysiological recordings of serotoninergic neurons in the dorsal raphe nucleus of brain stem slices revealed no modification in the sensitivity of somatodendritic 5-HT1A autoreceptors in rats treated with diazepam according to the protocols A and B. However, under the conditions of protocol C, the potency of 8-OH-DPAT to depress the firing rate of serotoninergic neurons was significantly enhanced, as expected of a hypersensitivity of somatodendritic 5-HT1A autoreceptors. These data support the hypothesis that some functional changes in these receptors could occur during benzodiazepine withdrawal. However, they do not support the idea of a reduced anxiolytic efficacy of 5-HT1A receptor agonists as a result of prior treatment with a benzodiazepine.

Role of 5-HT1A receptors in the ability of mixed 5-HT1A receptor agonist/dopamine D2 receptor antagonists to inhibit methylphenidate-induced behaviors in rats

Behavioral effects produced by the indirect-acting dopamine receptor agonist, methylphenidate (40 mg/kg i.p.) were examined in rats after administration of the 5-HT1A receptor agonists (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and flesinoxan, the mixed 5-HT1A receptor agonist/dopamine D2 receptor antagonists buspirone and 1-[-4-fluorobenzoylamino)ethyl]-ethyl]-4-(7-methoxynaphthyl) piperazine (S 14506), the neuroleptics haloperidol and clozapine, and the sigma receptor ligand/partial 5-HT1A receptor agonist alpha-(4-fluorophenyl)-4-(5-fluoro-2-pyrimidinyl)-1-piperazine-butanol (BMY 14802). All of the compounds produced dose-related decreases in methylphenidate-induced stereotyped gnawing, and, as gnawing was inhibited, other methylphenidate-induced responses (i.e. sniffing, rearing and locomotion) appeared. Higher doses of haloperidol and buspirone, but none of the remaining compounds, inhibited these other responses, so that the behavior of the methyphenidate-treated animals became similar to that of normal controls. Pretreatment with the 5-HT1A receptor antagonist N-[2-4-(2-methoxyphenyl)-1-piperazinyl]-ethyl]-N-(2-pyridinyl)- cyclohexanecarboxamide (WAY-100635; 0.63 mg/kg s.c.) blocked the ability of 8-OH-DPAT, S 14506 and flesinoxan to inhibit methylphenidate-induced gnawing, demonstrating the involvement of 5-HT1A receptors in their ability to inhibit methylphenidate-induced behaviors. In contrast, pretreatment with WAY-100635 did not alter the ability of haloperidol, clozapine, buspirone, or BMY 14802 to inhibit methylphenidate-induced gnawing, or in the case of haloperidol and buspirone, to normalize behavior. The results indicate that mixed compounds with 5-HT1A receptor agonist and dopamine receptor antagonist properties can be differentiated on the basis of the ability of WAY-100635 to reverse their effects on methylphenidate-induced behaviors.

Management of chronic pain. Part I

Chronic pain is associated with substantial psychosocial and economic stress, coupled with functional loss and various levels of vocational dysfunction. The role of a pain center is to focus on chronic pain in a multidisciplinary, comprehensive manner, providing the patient with the most effective opportunity to manage his or her chronic disease syndrome. This article focuses on methods to manage many types of chronic pain and describes a broad range of pharmacologic and nonpharmacologic interventions and options available to the patient. Part I of this two-part monograph describes pharmacotherapeutic interventions and regional nerve blocks. Part II focuses on psychologic assessment and treatment and physical therapy. A multimodal management strategy offers patients the greatest improvement potential for specific chronic pain syndromes. Cognitive and behavioral therapies and physical therapies are described. This combination of therapies may provide patients with the skills and knowledge needed to increase their sense of control over pain. The integration of appropriate pharmacotherapeutic regimens, neural blockades, physical therapy, and psychologic techniques maximizes a patient's effectiveness in dealing with chronic pain. Three case studies are presented in Part II.

Recent developments in anxiety, stress, and depression

Recent research in the development, analysis, and pharmacology of animal tests of state anxiety is discussed, including the use of responses to predator odours, the role of learning in modifying the anxiety measured in the plus-maze, and the roles of cholinergic, NMDA, and dopaminergic systems. Developmental and genetic factors are considered with particular reference to the development of tests of trait anxiety. The roles of 5-HT1A receptors in anxiety, depression, impulsivitity, and agonistic behaviours are discussed. Recent studies on the impacts of stress on neurotransmitter, endocrine, and immune systems and the interactions between these systems are discussed, with particular emphasis on their contributions to the development of pathologic states relevant to anxiety and depression.

[18F]fluoroalkyl analogues of the potent 5-HT1A antagonist WAY 100635: radiosyntheses and in vivo evaluation

Two analogues of the potent 5-HT1A antagonist WAY 100635 have been synthesized and radiolabelled with 18F, namely N-[2-[4-(2-2'-[18F] fluoroethoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohe xan e carboxamide ([18F]FEC) and N-[2-[4-(2-3'-[18F] fluoropropoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cycloh exa ne carboxamide ([18F]FPC). Biodistribution studies in rats showed selective uptake of both radiotracers in regions known to be rich in 5-HT1A receptors following i.v. injection. The ratio of radioactivity in hippocampus to that in the cerebellum was 5.5 (for [18F]FEC) and 7.5 (for [18F]FPC) at 60 min postinjection. Regional brain heterogeneity of radioactivity could be abolished by pretreatment with WAY 100635 and FPC but was unaffected by pretreatment with a variety of drugs including ketanserin, sulpiride, and SCH 23390. These results are compared vis-a-vis with those obtained using [11C]WAY 100635 to evaluate [18F]FEC and [18F]FPC as potential radiotracers for imaging 5-HT1A receptors by positron emission tomography.

Anxiolytic effects in the plus-maze of 5-HT1A-receptor ligands in dorsal raphé and ventral hippocampus

The response of rats naive to, or experienced with, the elevated plus-maze test of anxiety was observed following direct administration of the 5-HT1A-receptor agonist (+/-)-8-hydroxy-dipropylaminotetralin (8-OH-DPAT) (50, 100, or 200 ng) or antagonist tertatolol (3 micrograms) into the dorsal raphé nucleus or bilaterally into the ventral hippocampus. In rats naive to the plus-maze, neither drug had a significant effect when microinjected into the dorsal raphé nucleus. However, in rats experienced with the plus-maze, 8-OH-DPAT (100 and 200 ng) had significant anxiolytic effects when administered to the dorsal raphé nucleus, which were antagonised by tertatolol (3 micrograms); this suggests they were mediated by 5-HT1A receptors. Hyperactivity (increased number of closed-arm entries) was found following bilateral injection of 8-OH-DPAT (100 ng) into the ventral hippocampus of rats naive to the plus-maze. This was not completely antagonised by tertatolol (3 micrograms). Interestingly, tertatolol (3 micrograms) itself had an anxiolytic effect which was not antagonised by 8-OH-DPAT (100 ng), suggesting the effect was not mediated by 5-HT1A receptors, and indeed other actions of tertatolol, such as those on 5-HT1B or beta-adrenergic receptors could have been involved. In rats experienced with the plus-maze, tertatolol (3 micrograms) again had a significant anxiolytic effect when administered bilaterally to the ventral hippocampus, and again, this was not antagonised by 8-OH-DPAT (100 ng). These results demonstrate that both the intracerebral location of the injection and test experience profoundly influence the effects of 5-HT1A ligands on behaviour of rats in the elevated plus-maze test of anxiety.

Fenfluramine-induced activation of the immediate-early gene c-fos in the striatum: possible interaction between serotonin and dopamine

DL-Fenfluramine, a serotonin (5-HT) releasing agent, induces rapid expression of Fos-like immunoreactivity (Fos-LI) in the striatum as well as in other brain structures receiving a dense 5-HT innervation. Fenfluramine-induced Fos-LI expression in the striatum may result directly from the activation of 5-HT receptors or may be the result of interactions between dopamine (DA) and 5-HT neurotransmitter systems. To discriminate between these two possibilities, various groups of rats were pretreated with different 5-HT antagonists or a DA D1 antagonist, 20 min before fenfluramine administration. Animals were killed 60 min later. In the striatum, fenfluramine-induced expression of Fos-LI was almost completely blocked by SCH 23390, methysergide and S(-)-propranolol. The immediate-early gene response to fenfluramine was only slightly affected by pretreatment with the 5-HT2A/2C antagonist ritanserin. Fenfluramine was also administered to sham-operated and to unilaterally 6-hydroxydopamine (6-OHDA)-lesioned rats. In the 6-OHDA-lesioned rats, fen-fluramine-induced Fos-LI was decreased by 60% on the DA denervated side compared to the intact side and to sham-operated rats. To further probe the possibility of a direct activation of Fos-LI by 5-HT receptor subtypes, we evaluated the expression of Fos-LI after the administration of different 5-HT agonists. Our results demonstrate that neither 8-OH-DPAT, CGS-12066B, RU 24969 nor phenyl-biguanide was able to reproduce the effects of fenfluramine. Only a high dose of DOI (8.5 mg/kg) produced a moderate expression of Fos-LI in the dorsomedial part of the striatum. This contrasted with the Fos-LI expression in other brain areas where 8-OH-DPAT and DOI (2.5 and 8.5 mg/kg) reproduced the effects of the 5-HT releasing agent. Our results suggest that the release of 5-HT by fenfluramine induced Fos-LI expression predominantly in a striatal region related to associative functions and, that this c-fos response may be under the control of both 5-HT and DA. Moreover, the mechanism by which fenfluramine induces c-fos expression in the striatum differs from other brain regions.

Preference for diazepam, but not buspirone, in moderate drinkers

The purpose of the present study was to determine the preference for buspirone, an anxiolytic predicted to have minimal abuse potential, in comparison with diazepam in moderate drinkers. Preference for diazepam and buspirone was assessed in 55 moderate drinkers using a seven-session procedure consisting of four sampling sessions followed by three choice sessions. On each sampling session subjects ingested five capsules, one every 30 min. Color-coded capsules contained placebo on two sessions and drug on two sessions. Each drug capsule contained diazepam (4 mg) for 30 subjects and buspirone (5 mg) for 25 subjects. On choice sessions subjects chose whichever of the two color-coded capsules, i.e., drug or placebo, they wished to take. After ingesting one capsule, every 30 min they had the option of ingesting another capsule of the same color and content, for a maximum of seven capsules over the session (maximum of 28 mg diazepam or 35 mg buspirone). In the diazepam group 70% of subjects chose diazepam over placebo on at least two of the three choice sessions, whereas in the buspirone group only 24% of subjects chose buspirone over placebo on at least two sessions. Both diazepam and buspirone increased measures of sedation. Only diazepam increased ratings of liking and impaired performance, whereas only buspirone decreased ratings of feeling Friendly. These results replicate previous findings indicating that diazepam has reinforcing effects in moderate drinkers. Further, these results demonstrate the pharmacological specificity of this effect by showing that buspirone did not function as a reinforcer under these same conditions.

Kappa opioid agonists produce anxiolytic-like behavior on the elevated plus-maze

The selective kappa agonist U-50,488H was evaluated on the elevated plus-maze test of anxiety. U-50,488H was administered intraperitoneally to male Sprague-Dawley rats 20 min before testing, first in an open field apparatus, then followed immediately on the elevated plus-maze. No significant change in spontaneous locomotor activity was measured in the open field apparatus, suggesting that U-50,488H was devoid of sedative effects in the dose range tested (0.1-1000 micrograms/kg, IP). Doses between 10 and 1000 micrograms/kg produced significant increases in elevated plus-maze behavior that were consistent with anxiolytic actions for U-50,488H. These anxiolytic-like effects were antagonized by naloxone (2.0 mg/kg, IP), suggesting an opioid receptor site of action. In addition, we tested the kappa 1-selective U-50,488H-derivative, U-69,593 (100 micrograms/kg, IP), which was also shown to mimic the anxiolytic-like effects produced by U-50,488H. These results suggest that low doses of the selective kappa 1 agonists U-50,488H and U-69,593 are endowed with anxiolytic properties in rodents and that the kappa opioid system may be involved in the behavioral response to anxiety.

Thigmotaxis as an index of anxiety in mice. Influence of dopaminergic transmissions

When mice are introduced into an open-field, they are inclined to explore mainly the peripheral zone of this open-field. This tendency to remain close the walls, called thigmotaxis, decreases gradually during the first minutes of exploration. We have considered the degree of thigmotaxis during this period of decrease as an index of anxiety in mice. This hypothesis has been validated with several reference anxiogenic drugs (dexamphetamine, pentylenetetrazole, yohimbine, idazoxan) which increased thigmotaxis; and with anxiolytic drugs (buspirone, phenobarbital), which reduced it. On this test the selective or non-selective indirect dopamine agonists GBR 12783, dexamphetamine and cocaine induced an increase of thigmotaxis. Finally, the simultaneous involvement of D1 and D2 dopamine receptors has been evidenced in the anxiogenic-like effect associated with an increase of dopaminergic transmissions.

Anxiolytic and antidepressant mechanisms of 5-HT1A drugs in the pigeon: contributions from behavioral studies

The discovery that compounds acting through 5-hydroxytryptamine (5-HT) receptor subtypes can produce anxiolytic and/or antidepressant therapeutic effects in humans has resulted in considerable interest in the role of the 5-HT receptor system in both anxiety and depressive disorders. Because many of the clinically efficacious 5-HT1A anxiolytic drugs are either ineffective or produce inconsistent results in traditional or standard types of preclinical punishment or conflict procedures with rodents and other nonhuman mammals, there is considerable need for alternative behavioral assays sensitive to and selective for these compounds. In contrast to data with nonhuman mammals, 5-HT1A drugs are quite effective in pigeons studied under a punishment procedure. This paper reviews the use of the pigeon conflict procedure as a method for the detection and analysis of potential anxiolytic drugs acting through 5-HT1A receptors. Additionally, recent studies, also with the pigeon, have indicated that, in contrast to the rat, it is possible to establish an antidepressant such as imipramine as a discriminative stimulus, and then to use this procedure to evaluate the neuropharmacological bases for the behavioral and, presumably, therapeutic actions of these drugs. Using the drug discrimination procedure, it has been possible to examine a number of selective compounds that substitute for imipramine, thereby clarifying specific substrates for the antidepressant activity of this and related drugs. The pigeon promises to be a useful species in the pharmacological analyses of novel anxiolytic drugs and provides new approaches to the analysis and understanding of traditional as well as the more recently introduced antidepressant drugs.

Assessment of the dependence potential of the potent high-efficacy 5-HT1A agonist S-14506 in rats

This study assessed the dependence potential of S-14506 [ 1- [ 2-(4-fluorobenzoylamino)ethyl]-4-(7-methoxy napthyl) piperazine], a novel, potent 5-HT(1A) full agonist with anxiolytic and antidepressant actions in animal models. The dependence potential of S-14506 was compared with that of the benzodiazepine (BZ) chlordiazepoxide (CDP). BZ withdrawal caused weight loss, aphagia and hyperthermia after chronic b.i.d. treatment for 21 days. None of these withdrawal effects were seen after similar b.i.d. S-14506 treatment at high doses. However, the acute pharmacological actions of CDP and S-14506 differed on a number of indices. Specifically, CDP increased food intake and body weight, whilst S-14506 decreased these measures, possibly due to the induction of the serotonin syndrome. Of particular interest was the observation that S-14506 induced marked hypothermia, to which complete tolerance developed very rapidly (after only 1 day). The observation of marked, rapid tolerance to S-14506-induced hypothermia, in conjunction with the absence of withdrawal hyperthermia after prolonged chronic treatment at high doses, suggests that tolerance to this effect of S-14506 can be dissociated from dependence. Collectively, the data reported suggest that the full 5-HT(1A) agonist S-14506 is devoid of dependence potential, other human and animal studies having previously suggested that partial 5-HT(1A) agonists typically induce no, or minimal, dependence.

Electrophysiological evidence for a large receptor reserve for inhibition of dorsal raphe neuronal firing by 5-HT1A agonists

Previous studies [Meller et al. (1990) Mol. Pharmacol., 37:231-237] have shown that a large receptor reserve exists for the inhibition of serotonin synthesis in rat cortex and hippocampus by the 5-HT1A agonist 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT), whereas little or no reserve exists for the lower efficacy agonists ipsapirone and BMY 7378. The current studies were undertaken to determine if the above drugs exhibit similar relative efficacies and receptor reserves in an electrophysiological model of 5-HT1A receptor activation, i.e., the inhibition of dorsal raphe cell firing. Intravenous dose-response curves were constructed in untreated control rats, or in rats which received an injection of the irreversible receptor inactivator N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ, 6 mg/kg, s.c.) 24 hours before recording. All three drugs fully inhibited dorsal raphe cell firing in control rats (ED50's: 1.5 micrograms/kg, 8-OH-DPAT; 30.0 micrograms/kg, ipsapirone; 17.5 micrograms/kg, BMY 7378). However, unlike effects on serotonin synthesis, EEDQ treatments caused no depression of the maximal inhibitory response for any of the agonists, although all dose-response curves were shifted to the right (ED50's: 10.1 micrograms/kg, 6.7-fold shift, 8-OH-DPAT; 139.9 micrograms/kg, 4.7-fold shift, ipsapirone; 53.8 micrograms/kg, 3.1-fold shift, BMY 7378). Although the order of agonist efficacies was similar for both inhibition of serotonin synthesis and dorsal raphe cell firing (8-OH-DPAT > ipsapirone > BMY 7378), a large (> 50%) receptor reserve was estimated for all three drugs in this electrophysiological system.(ABSTRACT TRUNCATED AT 250 WORDS)

Nicotinic receptor agonists exhibit anxiolytic-like effects on the elevated plus-maze test

The effects of nicotinic receptor agonists on the elevated plus-maze test of anxiety were investigated in CD1 mice after intraperitoneal injections. Nicotine and lobeline, but not cytisine, exhibited a significant increase in the time spent by the mice in the open arms, a measure of anxiolytic activity. Nicotine also increased the total number of arm entries, a measure of general activity, but this effect was secondary to its anxiolytic-like properties. Nicotinic receptor antagonists on their own did not modify the behavior of mice in the maze. The effect of nicotine was mediated by central nicotinic receptors as it was blocked by the centrally-acting nicotinic antagonists mecamylamine and chlorisondamine, but not by hexamethonium (a peripherally acting blocker). Cotinine, the major metabolite of nicotine, was evaluated at different times after systemic injections and had no effect in the plus-maze. The anxiolytic-like profile induced by nicotinic receptor stimulation was not associated with potentiation of alcohol effects, a liability associated with the benzodiazepine therapy. This study demonstrates the anxiolytic-like properties of nicotine and lobeline in mice, and suggests that central nicotinic receptors are involved in the expression of emotional behavior.

Effects of 5-HT1A receptor agonists on patterns of rat motor activity in relation to effects on forebrain monoamine synthesis

The effects of the 5-HT1A receptor agonists 8-OH-DPAT (0.15-2.5 mumol kg-1 subcutaneously), flesinoxan (0.6-10.0 mumol kg-1 subcutaneously) and buspirone (1.9-30.0 mumol kg-1 subcutaneously) on spontaneous motor activity in male Sprague-Dawley rats was examined in a photocell-equipped open-field arena. Following motor activity observations, the cerebral aromatic L-amino acid decarboxylase inhibitor NSD-1015 (100 mg kg-1 intraperitoneally) was administered and 30 min. later the animals were decapitated for subsequent analysis of the accumulated forebrain DOPA and 5-HTP levels, as an estimate of the rate of monoamine synthesis. 8-OH-DPAT and flesinoxan produced a similar and characteristic pattern of changes of the spontaneous motor activity in normal animals i.e. a moderate decrease in locomotor activity, a marked suppression of rearing and an increase in the relative amount of forward locomotion and of activity in the periphery of the open-field arena. This behavioural profile was closely related to a decrease in forebrain 5-HTP accumulation, indicating 5-HT receptor stimulation. In agreement with these observations buspirone also produced an increase in peripheral activity and a suppression of rearing. In contrast to effects by 8-OH-DPAT and flesinoxan, however, buspirone produced a further reduction of locomotor activity and reduced the forward locomotion. This difference in behavioural profile between buspirone and the other two compounds is probably explained by its DA receptor blocking properties, as indicated by an increased DOPA accumulation in the neostriatum. At least partially, 8-OH-DPAT, flesinoxan and buspirone, all antagonized reserpine-induced (5 mg kg-1 subcutaneously--16 hr) suppression of locomotor activity. This stimulation of locomotor activity in reserpine-treated rats is in all probability related to 5-HT1A receptor stimulation since concomitant DA D2 receptor blockade, in the case of buspirone, did not markedly affect this behavioural response.

Dihydroergosine: anticonflict effect in rats and enhancing effects on [3H]muscimol binding in the human brain post mortem

The anticonflict activity of the ergot alkaloid, dihydroergosine, a drug which binds to 5-hydroxytryptamine1 (5-HT1) receptors and to gamma-aminobutyric acidA (GABAA) receptor-associated Cl- ionophore, was studied in water-deprived rats. In vitro effects of this drug on [3H]muscimol and [3H]flunitrazepam binding to the crude synaptosomal pellet of the human frontal cortex post-mortem were also investigated. Dihydroergosine, given 2 h prior to testing, enhanced drinking under punished (0.8 mA) conditions, and diminished it under unpunished conditions. The mechanism of this effect was (-)-propranolol- and pindolol-insensitive and picrotoxin-sensitive. Flumazenil either failed to affect, or at a higher dose (10 mg/kg), counteracted the dihydroergosine-induced enhancement of punished drinking. This dose of flumazenil was itself anxiogenic. Dihydroergosine had mild sedative and analgesic properties. Low concentrations of dihydroergosine (10 nM to 100 microM) enhanced the binding of [3H]muscimol but not of [3H]flunitrazepam. The results suggest that dihydroergosine may possess anxiolytic properties presumably mediated by its specific action at the GABA/benzodiazepine/chloride channel complex.

Comparative involvement of 5-HT1, 5-HT2 and 5-HT3 receptors in stress-induced colonic motor alterations in rats

The role of 5-HT1, 5-HT2 and 5-HT3 receptors in the genesis of colonic motor alterations induced by emotional stress was evaluated in rats equipped with implanted nickel/chrome electrodes on the proximal colon and a catheter into the lateral ventricle of the brain. In control rats the frequency of colonic spike bursts increased from 7.6 +/- 1.3 to 16.8 +/- 1.3 per 10 min when the rats were placed in a test cage in which they had previously received electric footshocks. I.p. injection of methysergide (0.1 mg/kg) reduced by 54% the emotional stress-induced increase of colonic spike burst frequency, while a higher dosage (1 mg/kg) of methysergide had no effect. The i.p. injection of ketanserin (a 5-HT2 receptor antagonist, 0.1 and 1 mg/kg) or granisetron (a 5-HT3 receptor antagonist, 0.1 and 1 mg/kg) had no effect on emotional stress-induced colonic hyperkinesia. The i.p. injection of the 5-HT1A receptor agonists, buspirone (1 mg/kg) or 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino(tetralin) (0.05 and 0.1 mg/kg) or benzodiazepine (clonazepam, 1 mg/kg) significantly reduced or suppressed the emotional stress-induced increase of colonic spike bursts. Injected i.c.v., buspirone, but not 8-OH-DPAT, also reduced the emotional stress-induced hyperkinesia. Pretreatment with devazepide receptor (1 microgram/kg) antagonized the inhibitory effects of buspirone and 8-OH-DPAT injected i.p. on emotional stress-induced colonic hyperkinesia but did not alter the effects of clonazepam (1 mg/kg).(ABSTRACT TRUNCATED AT 250 WORDS)

Brain monoaminergic neurotransmission in the mediation of lordosis behavior in the female rat

The present paper reviews recent pharmacological evidence indicating an important role for central monoaminergic neurotransmission in the mediation of lordosis behavior in the female rat. Following the initial observations by Meyerson and his colleagues in the early 1960s, demonstrating an inhibitory serotonergic mechanism, continued studies have identified 5-hydroxytryptamine (5-HT) 5-HT1A receptors to be of particular importance. Stimulation of central 5-HT2 receptors appear to have an opposite role, i.e. facilitating the elicitation of the lordosis response. As regards brain dopaminergic neurotransmission, it appears that brain dopamine (DA) D2 receptors mediate an inhibitory effect on the lordosis behavior, whereas no distinct role has been ascribed to DA D1 receptors. The serotonergic and the dopaminergic mechanisms can be manipulated independently, perhaps indicating the operation of parallel mechanisms. Most of the evidence presented above has been obtained in experiments on ovariectomized female rats primed with subthreshold doses of estrogen. It appears, however, that at least the inhibitory effects mediated by serotonergic neurotransmission are not dependent on the presence of progesterone.

5-HT receptors as targets for the development of novel anxiolytic drugs: models, mechanisms and future directions

The introduction of buspirone for the treatment of anxiety, together with the eventual suggestion of a mode of action involving the serotonin (5-HT)1A receptor subtype, has generated considerable research activity and renewed interest in the potential role of 5-HT in anxiety. The further identification of multiple 5-HT1 receptors, coupled with the possibility that these subtypes potentially are involved in discrete biobehavioral regulation and pathophysiological conditions, has greatly expanded the search for tools capable of probing these receptors and has raised hopes for a new generation of more specific compounds to treat other disorders associated with the 5-HT system such as depression, aggression, and sleep and eating disturbances. The involvement of 5-HT in anxiety has prompted a careful reevaluation of several traditional areas of research. This has included those methods used in the in vivo evaluation of drugs in preclinical animal test procedures used to assess potential anxiolytic activity, as well as the mechanisms associated with adaptive changes occurring during long-term drug administration. The proliferation of various procedures for studying the anxiolytic effects of 5-HT drugs has not always been accompanied by systematic behavioral and pharmacological validation. At the present time, this area of research is characterized by numerous inconsistent findings. Procedures that are objective and impartial to the behavioral effects of drugs provide distinct advantages for addressing some of these issues, as will the results from carefully controlled clinical studies. The main objective of this article is to provide an overview of the recent developments in research involving the 5-HT system and anxiety. The emphasis will be on the 5-HT1 receptor system and a review of the results in the predominant animal models used to evaluate these drugs, as well as an overview of the mechanisms currently believed to be responsible for the therapeutic activity of this class of compounds. Studies with the pigeon are reviewed, since this species appears distinctly sensitive to the anxiolytic-like effects of 5-HT1A drugs in conflict procedures. Although chronic administration of 5-HT1A drugs appears necessary for clinical anxiolytic and antidepressant activity, the most noteworthy neuropharmacological effects in animals seem to occur in 5-HT2 and, perhaps, 5-HT3 receptors which are downregulated. Studies summarizing the activity of drugs interacting with 5-HT1C/2 and 5-HT3 receptor sites are also discussed as they too may be involved in anxiety or the actions of anxiolytic drugs.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of buspirone and gepirone on i.v. cocaine self-administration in rhesus monkeys

Buspirone and gepirone were evaluated as potential pharmacotherapies for cocaine abuse by studying the effects of acute and repeated treatment on IV cocaine self-administration in rhesus monkeys. Chlorpromazine was also evaluated as a positive control. Effects of IV drug pretreatments were tested during daily 60-min sessions with lever-pressing reinforced under a fixed-ratio 10 schedule of 0.02 or 0.05 mg/kg cocaine infusions. Acute pretreatment with buspirone (0.1 and 0.3 mg/kg, IV) increased rates of cocaine self-administration without disrupting food pellet consumption. Some doses of buspirone also produced changes in rates of cocaine self-administration without altering the within-session pattern of responding. In contrast, acute doses of gepirone had little effect on rates of cocaine self-administration, while disruptions in food consumption and changes in the within-session pattern of cocaine self-administration were obtained at the highest dose of gepirone tested (1.0 mg/kg). When either buspirone (0.1 and 0.3 mg/kg, IV) or gepirone (0.1 mg/kg, IV) were administered daily for 10 days, consistent effects on cocaine self-administration were not observed. Thus, the effects of acute buspirone administration on cocaine-maintained behavior were similar to the effects produced by chlorpromazine and other dopaminergic antagonists, whereas, gepirone was ineffective. These results provide some support for further evaluation of buspirone as a potential pharmacotherapy for cocaine abuse, although its lack of efficacy with repeated treatment is not encouraging. The negative results with gepirone provide less rationale for continued investigations with this drug, possibly because of its lesser involvement than buspirone with dopaminergic neurotransmission.