摘要
目的 观察内源性和外源性褪黑素对大鼠下丘脑视交叉上核神经元自发放电的影响。方法 在昼夜周期的不同时相 (主观白天的CT4～ 8和主观黑夜的CT16～ 2 0 ) ,采用松果腺摘除 (PINX)和氨甲蝶呤 (MTX)抑制褪黑素 (MEL)合成的方法 ,分别去除内源性MEL的主要来源后 ,观察大鼠SCN神经元自发放电的变化以及侧脑室注射外源性MEL的作用。结果 (1)不管是主观白天还是主观黑夜 ,SCN神经元存在规则放电、不规则放电和簇状放电 3种形式的自发放电 ,摘除松果腺和抑制MEL合成 ,对这 3种放电形式未见明显影响 ;(2 )SCN神经元的自发放电频率在主观白天高 ,在主观黑夜低。摘除松果腺和抑制MEL合成后 ,放电频率昼高夜低的节律性消失 ,放电频率有所提高 ;(3)SCN神经元对外源性MEL起抑制反应 ,高亲和力 (ML - 1)受体拮抗剂luzindole能阻断这种抑制效应 ,而低亲和力 (ML - 2 )受体拮抗剂哌唑嗪 (prazosin)则不能 ,提示MEL的抑制作用是由ML - 1受体介导的。结论 松果腺作为大鼠昼夜节律组构中的一个调整器 ,分泌MEL并由ML - 1受体介导 ,对SCN神经元自发放电有抑制性的调节作用。
Objective To observe the effects of endogenous and exogenous melatonin on the spontaneous firing of rat hypothalamic suprachiasmatic nucleus (SCN) neurons.Methods The spontaneous firing of SCN neurons was recorded in vivo extracellularly during the subjective day (CT4-8) and the subjective night (CT16-20) after pinealectomy (PINX) and after inhibition of endogenous melatonin (MEL) synthesis by methotrexate (MTX), and the effect of exogenous MEL on the neuronal firing of SCN was examined.Results (1) In the spontaneous firing of SCN neurons there existed three types of discharge (regular firing, irregular firing and burst firing), which persisted during both the subjective day and the subjective night, as well as after PINX and after inhibition of endogenous MEL synthesis.(2) The firing rate of SCN neurons was high during the subjective day and low during the subjective night, this circadian rhythm disappeared and the firing rate was increased after PINX and after inhibition of endogenous MEL synthesis.(3) The effect of exogenous MEL on SCN neurons was inhibitory in nature, which was blocked by ML-1 receptor antagonist luzindole, but not by ML-2 receptor antagonist prazosin.Conclusion The pineal gland ,as a regulator in circadian rhythm organization, secretes MEL, which, in turn,elicits an inhibitory regulatory effect on SCN neurons through ML-1 receptor.
出处
《苏州大学学报（医学版）》
CAS
2002年第2期137-140,156,共5页
Suzhou University Journal of Medical Science
