Two types of acetylcholine receptors on the soma of primary afferent neurons.

Acetylcholine (ACh) caused two types of depolarizations of the soma membrane of bullfrog primary afferent neurons (dorsal root ganglion cells); the one, a rapid transient depolarization, was nicotinic and the other, a long-lasting one, was muscarinic in nature, respectively. The rapid transient depolarization was due to a simultaneous increase in sodium and potassium conductance, whereas the slow one was caused by a decrease in membrane potassium conductance. These results indicate that the soma of bullfrog primary afferent neuron is endowed with nicotinic and muscarinic receptors.