Functional organization of chromaffin cells and cholinergic synaptic transmissiom in rat adrenal medulla

Riichi Kajiwara, Olav Sand, Yoshiaki Kidokoro, Michael E. Barish, Toshio Iijima

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    39 Citations (Scopus)

    Abstract

    Optical recordings of membrane depolarization and whole-cell patch-clamp recordings of membrane potentials and currents were obtained from chromaffin cells in slices of rat adrenal medulla. The stimulation of splanchnic nerve fibers caused a discontinuous spread of electrical activity across the slice. Cells in clusters with diameters of about 80 μm were excited simultaneously, suggesting that the adrenal medulla is organized into discrete cell complexes with common innervation. The electrical properties of chromaffin cells in situ were in agreement with previous reports on cultured cells. A fraction of the recorded cells displayed excitatory postsynaptic currents (EPSCs) of 0.2-1 nA upon the stimulation of presynaptic nerve fibers. The EPSC was blocked by hexamethonium, suggesting that nicotinic ACh receptors were involved. The decay phase of the EPSC was well fit by the sum of two exponentials with time constants of 6.3 and 57.3 ms. The relative amplitude of the fast component was 84.1%. These two exponentials may reflect activation of both fast and slow time-constant ACh receptor channels by presynaptic release of ACh. There were multiple peaks in the EPSC amplitude histograms in low-[Ca2+] saline, the first peak was at 37 pA. To resolve the quantal size, miniature EPSCs were recorded in a tetrodotoxin-containing high-[K+] solution. The miniature EPSC amplitude histograms were also multimodal with the first peak at 25 pA, which probably represents the quantal size of the synapse. The second and third peaks were at the integer multiples of the first one.

    Original languageEnglish
    Pages (from-to)449-464
    Number of pages16
    JournalJapanese Journal of Physiology
    Volume47
    Issue number5
    DOIs
    Publication statusPublished - 1997 Oct

    Keywords

    • ACh
    • Chromaffin cells
    • EPSC
    • Quantal release
    • Rat adrenal medulla

    ASJC Scopus subject areas

    • Physiology

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