Behavioral responses of restricted-fed fowls to pharmacological manipulation of 5-HT and GABA receptor subtypes.

Effects on environmentally induced oral stereotypies (object pecking and drinker-directed activity) and other behavior (sitting, standing, pacing, preening), of preferential antagonists and agonists of central 5-HT and GABA receptor subtypes, were examined in individually caged broiler breeder fowls subjected to chronic food restriction. All drugs were injected intravenously at three doses, and their effects compared with a saline control treatment. The only significant (p < 0.05) effect of 5-HT antagonists [NAN-190 (5-HT1A), ketanserin (5-HT2), MDL-72222 (5-HT3)] was an increase in pacing with ketanserin (0.8 mg/kg). With 5-HT agonists, 8-OH-DPAT (5-HT1A) suppressed the two oral stereotypies and increased standing (all 1.0 mg/kg) and preening (0.2 mg/kg), alpha-methylserotonin (5-HT2) suppressed the oral stereotypies and increased sitting (all 1.0 mg/kg), and m-CPBG (5-HT3) suppressed drinker-directed activity (1.0 mg/kg). The GABA antagonists (bicuculline (GABAA), 5-aminovaleric acid (GABAB) had no effect, and of the GABA agonists [muscimol (GABAA), baclofen (GABAB)], muscimol suppressed preening and increased sitting, standing (all 1.0 mg/kg), and pacing (0.2 mg/kg). Most of the significant effects of serotonergic and GABAergic agents on behavior here appeared to reflect at least some degree of sedation, and there was no real evidence of any specific influence of these compounds on the oral stereotypies within the range of doses tested.