Synaptic Transmission and Modulation in Submandibular Ganglia. Aspects of a Current-Clamp Study.

Abstract

The superior salivatory nucleus in the medulla oblongata is the parasympathetic center of the sublingual and the submandibular (SM) glands. The preganglionic axons originating in this parasympathetic center connect postganglionic neurons in the submandibular ganglia. In spite of an earlier electrophysiological study by Langley in 189013), intracellular electrical studies on SM ganglion neurons had not been done because of the technical difficulties in impaling neurons. It was in only 1972 that the authors begun the intracellular electrical studies of SM ganglia in adult rats and hamsters. In this review, we describe the membrane properties of neurons, spontaneous activities of neurons, types of connection between pre- and post-ganglionic neurons, synaptic potentials including fast EPSP, slow IPSP, slow EPSP and slow hyperpolarizing synaptic potential, characteristics of the reflex spike discharges and modulation of synaptic transmission by biogenic substances in SM ganglion neurons. Transfer of information within the ganglia is more complex than simple nicotinic-cholinergic relay, and seems to be specialized for compatibility with the salivary glands. These data reflect the specific characteristics of synaptic transmission in the SM ganglia.