Elicitation of conspecific attack or defense in the male rat by intraventricular injection of a GABA agonist or antagonist.

The involvement of central GABAergic mechanisms in the control over offensive and defensive behaviours in the rat was studied using intracerebroventricular injections (5 microliter) of a GABA agonist (THIP) or a GABA antagonist (bicuculline methiodide). Intracerebroventricular injections of THIP (1.25 and 2.5 micrograms) induced attacks and offensive sideways towards an untreated partner, in animals placed in a neutral area where no aggressive reactions occur in controls. Social approach behaviours (partner investigation, allogrooming) were also increased in both attacking and non-attacking animals, whereas individual behaviours (cage exploration, autogrooming, immobile posture) were decreased. Inversely, intracerebroventricular injections of bicuculline methiodide (62.5 and 125 ng) suppressed offensive items (attacks, offensive sideways, upright postures) in resident animals confronted with untreated intruders and increased occurrence of defensive sideways. This treatment also decreased reactions oriented towards the partner (investigation, allogrooming and crawl under/over), while increasing individual behaviours (cage exploration, immobile posture). These data demonstrate that activation of central GABA receptors elicits intraspecific offensive behaviours in the rat. On the contrary, blockage of these receptors induces defensive reactions and suppresses offensive behaviours. The involvement of these receptors in the neural control over aggressive behaviour in the rat is discussed.