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The Journal of Neuroscience, May 1, 1999, 19(9):3367-3375
Differences in the Properties of Ionotropic Glutamate Synaptic Currents in Oxytocin and Vasopressin Neuroendocrine Neurons
Javier E. Stern, Mario Galarreta, Robert C. Foehring, Shaul Hestrin, and William E. Armstrong Department of Anatomy and Neurobiology, College of Medicine, University of Tennessee, Memphis, Tennessee 38163
Oxytocin (OT) and vasopressin (VP) hormone release from neurohypophysial terminals is controlled by the firing pattern of neurosecretory cells located in the hypothalamic supraoptic (SON) and paraventricular nuclei. Although glutamate is a key modulator of the electrical activity of both OT and VP neurons, a differential contribution of AMPA receptors (AMPARs) and NMDA receptors (NMDARs) has been proposed to mediate glutamatergic influences on these neurons. In the present study we examined the distribution and functional properties of synaptic currents mediated by AMPARs and NMDARs in immunoidentified SON neurons. Our results suggest that the properties of AMPA-mediated currents in SON neurons are controlled in a cell type-specific manner. OT neurons displayed AMPA-mediated miniature EPSCs (mEPSCs) with larger amplitude and faster decay kinetics than VP neurons. Furthermore, a peak-scaled nonstationary noise analysis of mEPSCs revealed a larger estimated single-channel conductance of AMPARs expressed in OT neurons. High-frequency summation of AMPA-mediated excitatory postsynaptic potentials was smaller in OT neurons. In both cell types, AMPA-mediated synaptic currents showed inward rectification, which was more pronounced in OT neurons, and displayed Ca2+ permeability. On the other hand, NMDA-mediated mEPSCs of both cell types had similar amplitude and kinetic properties. The cell type-specific expression of functionally different AMPARs can contribute to the adoption of different firing patterns by these neuroendocrine neurons in response to physiological stimuli.
Key words: oxytocin; vasopressin; hypothalamus; synaptic transmission; AMPA receptors; NMDA receptors
Copyright © 1999 Society for Neuroscience 0270-6474/99/1993367-09$05.00/0
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