Medial prefrontal transection enhances social interaction - II: Neurochemical studies

Medial prefrontal cortex (MPFC) transection enhances social interaction in an open arena test. Social interaction enhances dopaminergic activity in th e nucleus accumbens (NAC). In the present set of experiments, microdialysis probes were implanted in the NAG, and glutamate, gamma -aminobutyl ic acid (GABA) and dopamine IDA) were measured during electrical stimulation of th e MPFC, after coronal transection caudal to the MPFC and after a systemic i njection of amphetamine in transected rats. Electrical stimulation of the M PFC caused a transient enhancement of glutamate release in the NAG, no chan ge in GABA levels and a long lasting increase in DA levels. Medial prefront al transection did not change basal glutamate or GABA levels in the NAG, hu t increased basal DA levels. Amphetamine administration decreased GABA leve ls in medial prefrontal transected rats, had no effect on glutamate and inc reased DA levels more than in controls. The experiments suggest that glutam atergic activity in the accumbens decreases dopamine release. Medial prefro ntal transection reduces glutamatergic tone and enhances dopamine release, which probably decreases GABAergic activity in the NAC. Presumably, GABA in hibition in the NAC enhances social interaction. (C) 2000 Elsevier Science B.V. All rights reserved.