Blockade of the anxiolytic-like action of ipsapirone and buspirone, but not that of 8-OH-DPAT, by adrenalectomy in male rats

The effect of the 5-HT1A agonists ipsapirone (5 mg/kg), buspirone (5 mg/kg) and 8-OH-DPAT (0.5 mg/kg) on experimental anxiety was examined in sham-ope rated, adrenalectomized and adrenally demedullated male rats, The animal mo del of anxiety used was the defensive burying test. At the doses selected, all 5-MT1A compounds produced an anxiolytic-like action by reducing the bur ying behavior in both sham-operated and demedullated rats, However, in adre nalectomized subjects, while 8-OH-DPAT still reduced burying behavior, ipsa pirone and buspirone lost their action. Data suggest that adrenocortical se cretions play a role in the anxiolytic-like actions of buspirone and ipsapi rone. but not in those of 8-OH-DPAT. Buspirone and ipsapirone also produced a reduction in burying behavior latency in sham-operated animals that was not observed in adrenalectomized or adrenally demedullated rats. These data suggest that adrenaline may be participating in the action of these compou nds on the burying behavior latency. Present findings support possible dire ct relationships between the stimulation of 5-HT1A receptors and adrenal se cretions. (C) 1999 Elsevier Science Ltd. All rights reserved.