PMID: 7543799Jan 1, 1995Paper

Action of 5-hydroxytryptamine, substance P, thyrotropin releasing hormone and clonidine on spinal neuron excitability

The Journal of Spinal Cord Medicine
L E Tremblay, P J Bedard

Abstract

We investigated the influence of four substances on the excitability of lumbar motoneurons. These substances, three of which coexist in the same bulbospinal descending pathways that end, for the most part, around motoneurons (MNS), are: 5-hydroxytryptamine (5-HT), substance P (SP) and thyrotropin-releasing hormone (TRH). We also studied the effects of clonidine, an alpha 2 noradrenergic (NA) agonist. This study was carried out in rats spinalized at T5 and treated three weeks earlier with 5-7 dihydroxytryptamine (5-7 DHT). Under these conditions, the following responses were observed: 5-HTP (5-HT precursor) intraperitoneally (I.P.), 5-HT intrathecally (I.T.), TRH (I.P. or I.T.) and substance P (I.T.) all elicited strong excitation of MNS as measured by integrated EMG of the hindlimb muscles; substance P reduced by almost half the response to 5-HTP given one hour and 24 hours later; TRH given acutely did not modify the response to 5-HTP, but given chronically for 21 days markedly increased the response to this substance. Clonidine by itself decreased the excitability of MNS and antagonized the excitatory effects of 5-HTP and TRH. In two separate pilot trials, cyproheptadine, a 5-HTP antagonist, decreased the manifestations of spa...Continue Reading

Citations

Mar 16, 2007·Journal of Neurophysiology·Michelle M RankMonica A Gorassini
Mar 28, 2008·The Journal of Pharmacology and Experimental Therapeutics·Nicolas P LapointePierre A Guertin
Mar 1, 2005·Muscle & Nerve·C J HeckmannDavid J Bennett
Mar 24, 2004·Spinal Cord·J F DitunnoA S Burns
Apr 14, 1999·Gait & Posture·S KhodadadehJ Patrick

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