Alcohol, anxiolytics and social stress in rats

Abstract

The main objective was to compare the anxiolytic-like profiles of alcohol, diazepam and gepirone along the stress intensity gradient which characterizes consecutive phases of a social confrontation. The acute social stress situation consisted of initially placing the experimental rat as an intruder into the homecage of a resident while the resident was not present, termed the “anticipatory” phase, thereafter permitting brief physical agonistic interactions with the re-introduced resident until the intruder was forced into a submissive supine posture and emitted ultrasonic vocalizations (USV), and eventually exposing the intruder to the resident's threats for 1 h, while being shielded from potential injurious attacks. The hyperthermia, measured via telemetry, in the “anticipatory” phase prior to defeat and in reaction to threats, was decreased by alcohol, gepirone and diazepam; alcohol and gepirone were also effective in attenuating “anticipatory” tachycardia. Alcohol, like gepirone and diazepam, also decreased defensive responses and ultrasonic vocalizations in the “anticipatory” phase of the confrontation, but none of these drugs affected defensive reactions to threats which immediately followed defeat. Gepirone had no systematic sedative effects throughout the confrontation; infact, it dose-dependently reduced the stress-induced suppression of locomotor activity during the “anticipatory” phase. In contrast, at higher doses, alcohol as well as diazepam had marked sedative effects as evidenced by several behavioral parameters (i.e. lie, crouch, walk). The anxiolytic-like profile of hyperthermia, tachycardia, USV and defensive behavior in the “anticipatory” phase of the confrontation by alcohol, gepirone and diazepam contrasted with the lack thereof during the more intense reactive phase. This differential pattern of effects appears to be relevant to the clinical distinctions between anticipatory anxiety and other affective disturbances.