Early investigators of brain sti
mulation-evoked co
mplex behaviours (attack, escape, feeding, self-groo
ming, sexual behaviour) reported that experience
may affect the behavioural outco
me of brain sti
mulation. This intriguing exa
mple of functional neuronal plasticity was later totally neglected. The present experi
ment investigated the behavioural outco
me of in vivo
microdialysis perfusion of the gluta
mate agonist kainate and/or the GABAA antagonist bicuculline into the hypothala
mic attack area (HAA) of (1) ani
mals naive to dyadic encounters; (2) ani
mals with a recent aggressive experience (the probe being i
mplanted 6-24 h after the last of a series of dyadic encounters); and (3) ani
mals with an earlier aggressive experience (probe being i
mplanted 2 weeks after the last aggressive experience). On the experi
mental day, rats received two 5-
min infusions during a dyadic encounter lasting 35
min with an unknown opponent. Flow rate was 1.5-2
microliters/
min, drug concentrations were 1.8 x 10(-5) and 1.5 x 10(-5) M for kainate and bicuculline, respectively. Behaviour was analysed before, during and after perfusions. Only the co
mbined kainate + bicuculline treat
ment had significant effects on behaviour at the doses studied. A significant increase in aggressive behaviour was elicited only in ani
mals with a recent aggressive experience, while naive ani
mals and with an earlier experience responded to the treat
ments by groo
ming. These results appear to support early observations indicating that one i
mportant aspect of brain sti
mulation effects is previous experience.
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