Vasopressin-induced currents in rat neonatal spinal lateral horn neurons are G-protein mediated and involve two conductances.
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 microM) and tetrodotoxin (TTX)-resistant inward current. A role for G-proteins was indicated by persistence of this inward current after intracellular dialysis with GTP-gamma-S or GMP-PNP, its marked reduction with GDP-beta-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 Ih; 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.
Kolaj
M
M
Neuroscience, Loeb Research Institute, Ottawa Civic Hospital and University of Ottawa, Ottawa, Ontario K1Y 4E9, Canada.
Renaud
L P
LP
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D001127:Arginine Vasopressin / Q000494:pharmacology*; D004553:Electric Conductivity; D004594:Electrophysiology; D005260:Female; D019204:GTP-Binding Proteins / Q000502:physiology*; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010121:Oxytocin / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D017483:Receptors, Vasopressin / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*
D017483:Receptors, Vasopressin; D001127:Arginine Vasopressin; D010121:Oxytocin; D019204:GTP-Binding Proteins