Differential effects of phencyclidine upon hippocampal complex-spike and theta neurons

The effects of local application of phencyclidine (PCP) upon hippocampal CA1 neurons were investigated in urethane-anesthetized rats. Hippocampal neurons were classified on the basis of extracellularly recorded action potential duration as either complex-spike or theta cells prior to PCP administration. PCP depressed spontaneous firing of 46 of 48 complex-spike cells, but excited 12 of 13 theta neurons. This result demonstrates that hippocampal complex-spike and theta neurons may be differentiated of theta neurons were greatly attenuated or absent in rats pretreated with DSP4, a neurotoxin which selectively destroys noradrenergic pathways. This latter finding lends additional support to the hypothesis that the effects of locally applied PCP are mediated via noradrenergic mechanisms.