Nagano N, Ono H, Ozawa M, Fukuda H
Department of Toxicology and Pharmacology, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
Eur J Pharmacol. 1988 May 10;149(3):337-44. doi: 10.1016/0014-2999(88)90665-6.
The effects of thyrotropin-releasing hormone (TRH), 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) and L-5-hydroxytryptophan (5-HTP) were studied on the monosynaptic reflex (MSR) and the polysynaptic reflex (PSR) in acute and chronic spinal rats. Radioimmunoassay showed that while chronic spinal transection (for 2 weeks) caused the complete depletion of TRH in the ventral lumbar enlargement a certain level of TRH was maintained in the dorsal lumbar enlargement. This result suggested the existence of TRH-containing neurons in the dorsal horn other than the medullary raphe neurons descending to the spinal cord. The latency to the start of the MSR was shortened in chronic spinal rats and the amplitudes of the MSR and PSR were significantly greater than those in acute spinal rats. There was no obvious difference in the effects of TRH and 5-MeODMT on spinal reflexes of acute and of chronic spinal rats although marked supersensitivity to 5-HTP was observed in both the MSR and the PSR in chronic spinal rats. The supersensitivity to 5-HTP was considered to be due to a lack of 5-hydroxytryptamine (5-HT) uptake into 5-HT-containing nerve terminals rather than to a change in 5-HT receptors. It is suggested that TRH and 5-HT do not show any mutual requirement for each other in their effects on the spinal reflex since co-depletion of TRH and 5-HT did not change the effects of TRH and 5-MeODMT in chronic spinal rats. The coexistence of 5-HT and TRH in the descending spinal pathway is not considered to be significant for the control of spinal reflexes at the postsynaptic level.
研究了促甲状腺激素释放激素（TRH）、5-甲氧基-N，N-二甲基色胺（5-MeODMT）和L-5-羟色氨酸（5-HTP）对急性和慢性脊髓损伤大鼠单突触反射（MSR）和多突触反射（PSR）的影响。放射免疫分析表明，虽然慢性脊髓横断（2周）导致腰膨大腹侧TRH完全耗竭，但腰膨大背侧仍维持一定水平的TRH。这一结果提示，除了延髓中缝神经元下行至脊髓外，背角中还存在含TRH的神经元。慢性脊髓损伤大鼠MSR起始潜伏期缩短，MSR和PSR的幅度明显大于急性脊髓损伤大鼠。TRH和5-MeODMT对急性和慢性脊髓损伤大鼠脊髓反射的影响无明显差异，尽管在慢性脊髓损伤大鼠的MSR和PSR中均观察到对5-HTP的明显超敏反应。对5-HTP的超敏反应被认为是由于含5-羟色胺（5-HT）的神经末梢缺乏5-羟色胺摄取，而不是5-HT受体的改变。提示TRH和5-HT在对脊髓反射的作用中彼此之间没有相互需求，因为TRH和5-HT的共同耗竭并未改变慢性脊髓损伤大鼠中TRH和5-MeODMT的作用。5-HT和TRH在下行脊髓通路中的共存对于突触后水平的脊髓反射控制并不重要。
