Mechanisms of neuroprotection and retain the function of central nervous system during hibernation in Syrian hamsters

采用原代培养的仓鼠海马神经元，研究了腺苷（ADO）、阿片类物质、组胺和促甲状腺激素释放激素（TRH）等冬眠调节物质（HRS）对低温诱导的细胞死亡（LTCD）的保护作用。当培养物在<22℃下保持7天时，诱导LTCD。ADO（10-100 μM）对培养的神经元有剂量依赖性的保护作用。ADO的神经保护作用可被A_1受体拮抗剂8-环戊茶碱（CPT）和A_2受体拮抗剂3，7-二甲基-1-炔丙基半胱氨酸（DMPX）逆转。吗啡（一种非选择性阿片受体激动剂）在体外剂量范围为10-100 μM时也能有效减弱LTCD。吗啡的神经保护作用可被非选择性阿片受体拮抗剂纳洛酮拮抗。此外，虽然[D-Ala^2，N-Me-Phe ^4，Gly-ol^5]-脑啡肽（DAMGO; μ-阿片受体激动剂）、[D-Pen^<25>]-脑啡肽（DPDPE; δ-阿片受体激动剂）和[D-Gly-ol ^5]-脑啡肽（DAMGO; μ-阿片受体激动剂）在阿片受体激动剂中的作用不明显，但它们在阿片受体激动剂中的作用也不明显。 ...更多信息 st）和K-阿片受体激动剂U-69593也能有效抑制海马神经元的LTCD，TRH对培养的海马神经元LTCD无影响。此外，组胺在100 μM时可使叙利亚仓鼠体温降低，并在体外保护海马神经元。组胺的神经保护作用可被H_1受体拮抗剂吡拉明逆转。细胞凋亡可能参与了LTCD的发生。上述结果提示，ADO通过激动A_1和A_2受体对离体海马神经元起保护作用，而吗啡可能通过激动μ、δ和k阿片受体起神经保护作用。此外，组胺还通过激动H_1受体对海马神经元产生保护作用。因此，HRS-like腺苷-，阿片-和组胺-like低温行动将最有可能诱导对LTCD在体外的神经保护作用。内源性阿片肽参与冬眠期间体温（Tb）的中枢调节系统在叙利亚仓鼠。根据Tb的变化，将麻木分为i）进入期、ii）维持期和iii）唤醒期。在以往的研究中，我们证明了在维持阶段，中枢阿片系统参与Tb的调节系统。免疫组化法检测c-Fos和β-内啡肽的表达。侧脑室（icv）注射μ1阿片受体拮抗剂纳洛嗪（naloxonazine）可使金黄地鼠苏醒。相比之下，10 nM纳曲吲哚（δ-阿片受体拮抗剂）和nor-BNI（k-阿片受体拮抗剂）均未中断麻痹。侧脑室注射抗β-内啡肽抗体可有效地阻断昏睡，而抗内啡肽-1和-2抗体则无效。与麻痹前相比，麻痹后1h弓状核（ARC）内c-Fos阳性神经元数明显增多。此外，虽然前阿黑皮素（POMC）mRNA的表达水平没有变化，内切蛋白酶-2 mRNA的增加，在ARC。ARC内可见Β-内啡肽样免疫反应（β-EndIR）。随着冬眠的进行，ARC的β-End IR降低，而OVLT的β-End IR升高。提示β-内啡肽通过轴突流从ARC转运到OVLT，并通过μ1阿片受体调节体温。少

The neuroprotective effects of hibernation-regulating substances (HRS) such as adenosine (ADO), opioids, histamine and thyrotropin-releasing hormone (TRH) on low temperature-induced cell death (LTCD) were examined using primary cultured hamster hippocampal neurons. LTCD was induced when cultures were maintained at <22℃ for 7 days. ADO (10-100 μM) protected cultured neurons from LTCD in a dose-dependent manner. The neuroprotective effects of ADO were reversed by both 8-cyclopenthyltheophilline (CPT, A_1 receptor antagonist) and 3,7-dimethyl-1-propargybcanthine (DMPX; A_2 receptor antagonist). Morphine (a non-selective opioid receptor agonist) was also effective in attenuating LTCD at an in vitro dose-range of 10-100 μM. The neuroprotective effects of morphine were antagonized by naloxone (a non-selective opioid receptor antagonist). In addition, although [D-Ala^2, N-Me-Phe^4, Gly-ol^5]-enkephalin (DAMGO; μ-opioid receptor agonist), [D-Pen^<25>]-enkephalin (DPDPE; δ-opioid receptor agoni … More st) and U-69593 (k-opioid receptor agonist) were also effective, LTCD of cultured hippocampal neurons was not affected by TRH. Furthermore, histamine produced hypothermia in Syrian hamsters and protected hippocampal neurons in vitro at 100 μM. The neuroprotective effect of histamine was reversed by pyrilamine (H_1 receptor antagonist). Apoptosis was probably involved in LTCD. These results suggest that ADO protected hippocampal neurons in vitro via its agonistic actions on both A_1 and A_2 receptors, while morphine probably elicited its neuroprotective effects via agonistic effects on the μ-, δ- and k-opioid receptors. In addition, histamine also protected hippocampal neurons via its agonistic action on the H_1 receptor. Thus, HRS-like adenosine-, opioid- and histamine-like hypothermic actions would most likely induce neuroprotective effects against LTCD in vitro.Endogenous opioid peptides involved in the central regulatory system of body temperature (Tb) during hibernation in Syrian hamsters. The torpor was classified into i) entrance, ii) maintenance and iii) arousal phases according to Tb changes. In previous study, we demonstrated that central opioid system involved in the Tb regulatory system during maintenance phase. Immunostaining of c-Fos and β-endorphin was performed by using avidin-biotin-peroxidase procedure. Intracerebroventricular (icv) injection of naloxonazine (μ1-opioid receptor antagonist) was effective in arousing hamster from torpor. In contrast, neither 10 nM of naltrindole (δ-opioid receptor antagonist) nor nor-BNI (k-opioid receptor antagonist) interrupted the torpor. Moreover, icv injection of anti-β-endorphin antibody was effective in interrupting the torpor, but anti-endomorphin-1 and-2 antibodies were ineffective. The number of c-Fos positive neuron increased in arcuate nucleus (ARC) at 1 hr after torpor onset compared with before torpor. Furthermore, although the expression level of proopiomelanocortin (POMC) mRNA did not change, the endoprotease-2 mRNA incresed in ARC. Β-Endorphin-like immunoreactivity (β-End IR) was observed in ARC. With progress of hibernation, the β-End IR decreased with ARC and increased with organum vasculosum lamina terminalis (OVLT) . These results suggest that the β-endorphin was transported to OVLT from ARC by axonal flow and then regulates body temperature during maintenance phase of torpor via μ1-opioid receptors. Less