cis-Flupentixol antagonism of the rat prefrontal cortex neuronal response to apomorphine and ventral tegmental area input.

This study was designed to characterize the response of a select population of prefrontal cortex neurons to exogenous and endogenous dopaminergic influences. Of particular interest were neurons with efferent projections to the ventral tegmental area (VTA) which are part of a reciprocal innervation between the prefrontal cortex and the VTA. Extracellular single unit recording techniques were used to determine the response of cortical neurons to electrical stimulation of the VTA in chloral hydrate anesthetized rats. The neurons were selected on the basis of their electrophysiological characteristics (large amplitude with positive initial deflection) and were classified as to whether or not they were antidromically activated from the VTA. Apomorphine (25 micrograms/kg, IV) significantly reduced the spontaneous activity of both the antidromically identified and the unidentified prefrontal cortex neurons. The apomorphine (25 micrograms/kg, IV) response was antagonized by cis-flupentixol (1.0 mg/kg, IV) in both antidromically identified and unidentified cortical neurons. Stimulation of the VTA also induced a synaptically mediated inhibition of the cortical neuron spontaneous activity. The orthodromic VTA stimulus-evoked inhibition was antagonized by cis-flupentixol (1.0 mg/kg, IV) for both the antidromically identified and the unidentified neurons (63 and 71% of the neurons respectively). The results indicate that a select population of prefrontal cortex neurons respond specifically to exogenous and endogenous dopaminergic influences and that the response is independent of efferent projections to the VTA.