Synaptic activation of rat adrenal medulla examined with a large photodiode array in combination with a voltage-sensitive dye

T. Iijima, G. Matsumoto, Y. Kidokoro

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    39 Citations (Scopus)

    Abstract

    The adrenal medulla is innervated by sympathetic preganglionic nerve fibers in the splanchnic nerve. Synaptic activation of the adrenal medulla causes catecholamine secretion which is known to be modified by various neuropeptides and other factors. To understand the neuronal control mechanism of catecholamine secretion, it is necessary to know the transfer function at the synapse and how it is affected by such factors. By using a large photodiode array in combination with a voltage-sensitive dye, membrane potential changes in a slice of the rat adrenal gland were recorded upon brief local electrical stimulation. Electrical signals were recorded only on the portion of the diode array corresponding to the medulla. In a typical record, a spike and an underlying slow potential were observed following a small deflection due to a presynaptic nerve action potential. Both the spike and slow potential were blocked in Ca2+-free solution or by hexamethonium, a nicotinic antagonist, but were not affected by atropine, a muscarinic antagonist. The slow potential was interpreted as a nicotinic synaptic potential in the chromaffin cells and the spike as a population action potential. A double pulse experiment revealed that the chromaffin cell action potential began to fail only when the stimulus interval was less than 50 ms (20 Hz). When the stimulus intensity was reduced, the minimal response was found to behave in an all-or-none fashion. This suggested that one nerve fiber is innervating a cluster of chromaffin cells, which may correspond to a previously histologically identified "complex" of cells [Hillarp (1946) Acta. anat. 4, Suppl. 1]. Each complex was innervated by approximately four nerve fibers. Catecholamine secretion seems to be under tight neural control. Desensitization of acetylcholine receptors in the postsynaptic membrane is unlikely to play a significant role under normal conditions.

    Original languageEnglish
    Pages (from-to)211-219
    Number of pages9
    JournalNeuroscience
    Volume51
    Issue number1
    DOIs
    Publication statusPublished - 1992 Nov

    ASJC Scopus subject areas

    • Neuroscience(all)

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