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外文期刊>european journal of neuroscience
>A Study of the Barium‐sensitive and ‐insensitive Components of the Action of Thyrotropin‐releasing Hormone on Lumbar Motoneurons of the Rat Isolated Spinal Cord
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A Study of the Barium‐sensitive and ‐insensitive Components of the Action of Thyrotropin‐releasing Hormone on Lumbar Motoneurons of the Rat Isolated Spinal Cord
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机译：A Study of the Barium‐sensitive and ‐insensitive Components of the Action of Thyrotropin‐releasing Hormone on Lumbar Motoneurons of the Rat Isolated Spinal Cord
AbstractThe electrophysiological action of thyrotropin‐releasing hormone (TRH) on rat spinal motoneurons was studiedin vitrousing single‐electrode voltage‐ and current‐clamp techniques. In current‐clamp conditions TRH elicited a slowly developing depolarization, associated with a large input resistance increase and sustained neuronal firing; the primary metabolites of TRH were ineffective. Under voltage‐clamp conditions in the presence of tetrodotoxin, TRH evoked a large inward current (ITRH; peaking at approximately –40 mV) associated with a large input conductance fall. Only 44 of cells displayedITRHreversal; when the chord conductance values of these cells were plotted against membrane potential, a bell‐shaped relation occurred, indicating voltage‐dependent block by TRH of a persistent conductance active over a wide range of membrane potentials.ITRHreversal values were shifted to more positive levels in high K+solution in Nernstian fashion; hence a large proportion of the TRH response is suggested to be mediated by the block of a K+conductance (IK(T)).IK(T)(and its voltage‐dependent block by TRH) was resistant to certain K+channel antagonists (tetraethylammonium, Cs+, 4‐aminopyridine or apamin), but was depressed by Ba2+. The Ba2+‐resistant fraction ofITRHwas attenuated by Cd2+, Mn2+or Co2+, indicating that it probably involved a Ca2+‐sensitive inward current. Concomitant application of Ba2+and Cd2+induced a near‐total block of the response to TRH. It is suggested that suppression ofIK(T), associated with the onset of a Ca2+‐sensitive current, can explain the excitatory effect of
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