ELECTROPHYSIOLOGICAL PROPERTIES AND CHOLINERGIC RESPONSES OF RAT VENTRAL ORAL PONTINE RETICULAR NEURONS IN-VITRO

In order to characterize the electrophysiological properties of morpho logically identified neurons of the ventral part of the oral pontine r eticular (vRPO) nucleus and the effects of cholinergic agonists on the m, intracellular recordings were obtained from 45 cells in a rat brain -slice preparation. Intracellular staining was performed with 2% biocy tin in potassium acetate (1 M)-filled micropipettes. Results demonstra ted the presence of two types of vRPO neurons. Type I cells (n = 12, 2 4%) were characterized by a break with a decrease of the depolarizing slope following hyperpolarizing pulses which delayed the return to the resting V-m and subsequent spike-firing. The delay was antagonized by 4-AP (200-500 mu M) which specifically blocks the transient outward K f-mediated current I,. Type II neurons (n = 38, 76%) displayed a typic al depolarizing sag during hyperpolarizing current pulses which was bl ocked by Cs+. This behavior is characteristic of the hyperpolarization -activated current I-Q. These two neuronal types displayed different m orphological features. Most type I and LI cells (100 and 73.7%, respec tively) were depolarized by acetylcholine (1-15 mu M), carbachol(0.5-1 mu M) and muscarine (1-10 mu M) through the activation of post-synapt ic muscarinic receptors. The remaining type II cells (26.3%) were hype rpolarized (1-10 min, 3-15 mV) through the activation of post-synaptic muscarinic receptors. Results are consistent with the hypothesis that the vRPO could be a neuronal target of Cch in eliciting paradoxical s leep because most of its neurons are activated by muscarinic agonists. (C) 1979 Elsevier Science B.V.