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Neurotransmitter‐Mediated Changes in the Electrophysiological Properties of Pituicytes
Author(s) -
Burnard Diane M.,
Pittman Quentin J.,
MacVicar Brian A.
Publication year - 1991
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1991.tb00300.x
Subject(s) - endocrinology , medicine , opioid peptide , (+) naloxone , chemistry , agonist , neurotransmitter , enkephalin , resting potential , membrane potential , dynorphin , electrophysiology , depolarization , biophysics , antagonist , biology , receptor , opioid , central nervous system
Intracellular recordings were obtained from pituicytes in the neural lobe of the isolated rat pituitary. Like other glia, pituicytes lacked action potentials in response to depolarizing current injection, but they tended to have more positive resting membrane potentials and higher input resistances than astrocytes in other preparations. Dye‐coupling typical of astrocytes was also demonstrated amongst pituicytes, and their morphologies were similar to those of pituicytes stained for glial fibrillary acidic protein. Action potentials, anode‐break spikes or barium spikes were not observed in pituicytes, even under conditions that maximized the elicitation of Ca 2+ ‐dependent responses. This suggests that pituicytes either have no or a very low density of Ca 2+ channels or Ca 2+ currents that are too small to generate action potentials. Dynorphin A (1–13), a kappa‐opioid agonist, produced long‐lasting increases in pituicyte input resistance with no significant changes in resting membrane potential. Dynorphin's action was concentration‐dependent and was blocked by the opioid antagonist naloxone. This is consistent with previous reports demonstrating kappa‐opioid receptors on pituicytes in the neurohypophysis. The β‐adrenergic agonist isoproterenol (100 μM) reversed the increases in pituicyte input resistance produced by opioid application, with no significant changes in resting membrane potential. The fact that pituicytes responded to neurotransmitters suggests a functional link between pituicytes and neurosecretory nerve fibres.