GABA-Nitrergic Interactions in the Nucleus Accumbens during Inhibition of Exploratory Behavior by Danger Signals

Vital intracerebral microdialysis experiments in Sprague–Dawley rats with high-performance liquid chromatography (HPLC) showed that presentation during exploratory behavior of a tone previously combined with pain stimulation decreased exploratory activity and inhibited the exploratory behavior-induced increase in the extracellular citrulline (a co-product of NO synthesis) level in the medial sector of the nucleus accumbens. Administration of the GABA A receptor antagonist bicuculline (20 μM) into the medial sector of the nucleus accumbens firstly produced partial recovery of the increase in the extracellular citrulline level in this structure induced by exploratory behavior and suppressed by a tone previously combined with pain stimulation and, secondly, prevented inhibition of exploratory behavior by this danger sound signal. The data obtained here provide the first evidence that inhibition of exploratory behavior by danger signals and the exploration-associated activation of the nitrergic system of the medial sector of the nucleus accumbens are mediated by GABA A receptor mechanisms.