Vasopressin-Induced Currents in Rat Neonatal Spinal Lateral Horn Neurons Are G-Protein Mediated and Involve Two Conductances

Abstract

Kolaj, Miloslav and Leo P. Renaud. Vasopressin-induced currents in rat neonatal spinal lateral horn neurons are G-protein mediated and involve two conductances . J. Neurophysiol. 80: 1900–1910, 1998. Arginine vasopressin (AVP) receptors are expressed early in the developing spinal cord. To characterize AVP-induced conductances in lower thoracic sympathetic preganglionic (SPN) and other lateral horn neurons, we used patch-clamp recording techniques in neonatal (11–21 days) rat spinal cord slices. Most (90%) of 273 neurons, including all 68 SPNs, responded to AVP with membrane depolarization and/or a V1 receptor-mediated, dose-dependent (0.01–1.0 μM) and tetrodotoxin (TTX)-resistant inward current. A role for G-proteins was indicated by persistence of this inward current after intracellular dialysis with GTP-γ-S or GMP-PNP, its marked reduction with GDP-β-S, and significant reduction, but not abolition, after preincubation with pertussis toxin or in the presence of N-ethylmaleimide. Analysis of individual current-voltage ( I- V) relationships in 57 cells indicated the presence of two different membrane conductances. In 21 cells, net AVP-induced currents reversed around −103 mV, reflecting reduction in one or more barium-sensitive potassium conductances; in 12 cells, net AVP-induced current reversed around −40 mV and was not significantly sensitive to several potassium channel blockers including barium, tetraethylammonium chloride (TEA), 4-aminopyridine (4AP), cesium, or glibenclamide, suggesting increase in a nonselective cationic conductance that was separate from I h; in 24 cells where I- V lines shifted in parallel, AVP-induced inward currents were significantly greater and probably involved both conductances. These data indicate that SPNs and a majority of unidentified neonatal lateral horn neurons possess functional G-protein–coupled V1-type vasopressin receptors. The wide distribution of AVP receptors in neonatal spinal lateral column cells suggests a role that may extend beyond involvement in regulation of autonomic nervous system function.