PHYSIOLOGICAL PROPERTIES OF RAT VENTRAL PALLIDAL NEURONS RECORDED INTRACELLULARLY IN VIVO. Lavin, Antonieta and Anthony A. Grace. Departments of Neuroscience and Psychiatry, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA.
APStracts 2:0310N, 1995.
SUMMARY AND CONCLUSIONS
1. The physiology of ventral pallidal (VP) cells was investigated using in vivo intracellular recording and staining techniques in adult rats. Based on electrophysiological criteria, three different types of cells were found: a) Type A cells. Cells in this group fired phasic spikes that did not exhibit a substantial afterhyperpolarization (AHP). b) Type B cells. These cells exhibited a slow ramp-like depolarization that preceded the short duration action potential; the spike was followed by a prominent afterhyperpolarization (AHP). c) Type C cells. This was the only class of cells that fired spikes in couplets or bursts, with the spikes in a burst exhibiting a progressive increase in duration and a decrease in amplitude. These cells also exhibited a rebound low threshold spike-like event. Furthermore, 18% of the VP cells recorded exhibited a slow subthreshold oscillation of the membrane potential (<1 Hz). 2. The response of VP cells to stimulation of fibers arising from the prefrontal cortex (PFCtx), nucleus accumbens, and mediodorsal thalamic nucleus (MD) was examined. In contrast to our initial predictions, all cells responded to nucleus accumbens stimulation with excitation. Type A and Type B cells responded to nucleus accumbens stimulation with excitation and to MD stimulation with antidromic-like responses, orthodromic excitation, or evoked ipsps. Only Type A cells responded to prefrontal cortical stimulation. Type C cells only responded to stimulation of the nucleus accumbens, which resulted in evoked epsps. 3. The cells in the VP can therefore be segregated into three physiologically defined groups according to action potential discharge patterns and their response to afferent fiber stimulation. 

Received 12 July 1995; accepted in final form 24 October 1995.
APS Manuscript Number J447-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95