clozapine and gepirone

Behavioral and neurochemical effects of several drugs that increase punished responding were studied in pigeons. Key pecking was established under a schedule of reinforcement in which periods of food-maintained responding alternated with periods in which behavior also was suppressed by the presentation of electric shock. Buspirone (0.1-10.0 mg/kg), gepirone (0.1-1.0 mg/kg), 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; 0.1-3.0 mg/kg), chlordiazepoxide (3.0-30.0 mg/kg) and to a lesser extent clozapine (0.1-1.0 mg/kg) all produced increases in punished responding at doses having little effect on or decreasing the rate of unpunished responding. Neurochemical analyses on samples of cerebrospinal fluid after administration of several doses of each compound were performed for the dopamine metabolites homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC), the noradrenergic metabolite 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) and the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA). Gepirone, 8-OH-DPAT and the novel anxiolytic buspirone produced decreases in 5-HIAA at doses that increased punished responding in the behavioral studies. Buspirone increased levels of HVA and DOPAC, whereas its structural analog gepirone and the 5-hydroxytryptamine1A agonist 8-OH-DPAT had little effect on or decreased levels of these metabolites. Chlordiazepoxide, a prototypic benzodiazepine anxiolytic, produced only modest decreases in each of the metabolites studied. Clozapine, an atypical antipsychotic drug, produced increases in each of the metabolites studied, although only the 5-HIAA effect occurred at doses that were not behaviorally disruptive. Haloperidol (0.03-1.0 mg/kg) produced only decreases in punished and unpunished responding, whereas eliciting increases in the appearance of MHPG, DOPAC and HVA; levels of 5-HIAA were relatively unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 3,4-Dihydroxyphenylacetic Acid; Animals; Anti-Anxiety Agents; Buspirone; Chlordiazepoxide; Clozapine; Columbidae; Conditioning, Operant; Haloperidol; Homovanillic Acid; Hydroxyindoleacetic Acid; Male; Methoxyhydroxyphenylglycol; Punishment; Pyrimidines

The novel anxiolytic buspirone was administered to pigeons in a two-key drug discrimination task in an effort to characterize the stimulus properties of the drug and thereby aid in isolating the pharmacologic basis for its anticonflict effect. Key pecking was maintained by a schedule of reinforcement in which every 30th injection-appropriate response was reinforced by the presentation of food. Subjects were first trained to discriminate buspirone (1.0 mg/kg) from saline, and then generalization tests were conducted using a cumulative dosing procedure. Cumulative doses of buspirone (1.0-3.0 mg/kg), the buspirone analog MJ 13805 (1.0 mg/kg) and the 5-hydroxytryptamine-1A ligand 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (0.3-1.0 mg/kg) produced in excess of 90% buspirone-appropriate responding, whereas midazolam (0.03-1.0 mg/kg), haloperidol (0.03-1.7 mg/kg), apomorphine (0.03-1.0 mg/kg), clozapine (0.1-3.0 mg/kg), methysergide (0.1-3.0 mg/kg) and the 5-hydroxytryptamine-1B ligand 1-[3-chlorophenyl]piperazine (0.3-10.0 mg/kg) produced little or no buspirone-appropriate responding up to those doses that markedly decreased response rate. These findings support recent behavioral and receptor binding studies suggesting that serotonin receptors, and 5-hydroxytryptamine-1A receptors in particular, may be responsible for mediating the anticonflict effects of buspirone and other atypical anxiolytics. The results also corroborate other behavioral work showing that the anxiolytic effects of buspirone are most likely not mediated by the dopaminergic system.

Topics: Animals; Apomorphine; Buspirone; Clozapine; Columbidae; Discrimination Learning; Haloperidol; Methysergide; Midazolam; Pyrimidines; Serotonin