Neurochemical effects of verruculogen, a secondary fungal (Penicillium Verruculosum) metabolite, were studied using rat synaptosomes. To evaluate the presynaptic effects of verruculogen, high affinity uptake and potassium stimulated release, as well as spontaneous release of $^{3}H$-GABA from synaptosome enriched preparations from the hippocampus, corpus striatum, and cerebral cortex were investigated. High affinity uptake of $^{3}H$-GABA into hippocampal and striatal synaptosomes decreased by 36.7 and 26.2%, respectively, in the presence of 0.1 mM verruculogen, while $^{3}H$-GABA uptake in cerebrocortical synaptosomes showed no remarkable change. Verruculogen had no significant effect on the spontaneous or the stimulated release of $^{3}H$-GABA from hippocampal, striatal, and cortical synaptosomes. These results suggest that verruculogen exerts presynaptic effects on GABAergic nerve terminals by inhibiting high affinity uptake systems in the hippocampus and striatum.