An examination of glutamate decarboxylase₆₅ immunoreactive puncta with respect to rat ventral pallidum neurons after repeated cocaine administration

The ventral pallidum is known to have topographically organized reciprocal γ-aminobutyric acid-ergic projections with the nucleus accumbens, and changes in these connections may play a role in mediating the behavioral sensitizing effect of repeated exposure to cocaine. The present study investigated glutamate decarboxylase-65 (GAD₆₅) immunoreactivity in the rat ventral pallidum after repeated cocaine administration. Male Sprague-Dawley rats were administered bi-daily injections of 15 mg/kg cocaine or saline vehicle for 5 consecutive days. After 2 or 14 days of withdrawal, ventral pallidal sections were immunocytochemically processed for GAD₆₅ immunoreactive puncta and counts were made. In both groups, there were no statistically significant differences in the number or density of GAD₆₅ puncta in medial or lateral portions either in contact with neuronal cell bodies or in the neuropil after 2 or 14 days of withdrawal. The results suggest that there is no alteration in the number of GABAergic boutons expressing GAD₆₅ immunoreactivity in the ventral pallidum after repeated exposure to cocaine. Copyright (C) 2000 Elsevier Science Ireland Ltd.