Vasopressin depolarizes lateral horn cells of the neonatal rat spinal cord in vitro.
The effects of vasopressin (VP) on lateral horn cells including a number of sympathetic preganglionic neurons contained in thin in vitro slices of neonatal rat spinal cord were investigated by means of intracellular recording techniques. Superfusion of (Arg8)-vasopressin (AVP, 0.01-1 microM) caused a depolarization leading, in the majority of lateral horn cells, to repetitive discharges. The AVP depolarization which could be partially reduced by low Ca/high Mg solution or tetrodotoxin, was accompanied by an increase in membrane resistance and the response was nullified near the membrane potential at which the spike afterhyperpolarization was abolished. A clear reversal of the response was not observed upon further hyperpolarization. The AVP response was blocked by the VP1 antagonist, D-(CH2)5 Tyr (Me)-AVP, whereas, deamino (D-Arg8-vasopressin), a VP2 agonist, at high concentrations (greater than or equal to 50 microM) was either ineffective or produced a small depolarization. The results indicate that AVP, acting mainly on VP1 receptors, excited lateral horn cells by a direct depolarization and an indirect effect via the release of an excitatory transmitter(s). A reduction of a voltage-dependent K conductance may underlie the depolarizing effect of AVP.
D000818:Animals; D000831:Animals, Newborn; D001127:Arginine Vasopressin / Q000031:analogs & derivatives / Q000494:pharmacology*; D001339:Autonomic Fibers, Preganglionic / Q000187:drug effects; D002415:Cats; D002462:Cell Membrane / Q000187:drug effects; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D013116:Spinal Cord / Q000187:drug effects*; D013564:Sympathetic Nervous System / Q000187:drug effects*
D001127:Arginine Vasopressin; C025043:vasopressin, 1-(1-mercaptocyclohexaneacetic acid)-2-(O- methyl-L-tyrosine)-8-L-arginine-; D003894:Deamino Arginine Vasopressin