Gazyakan E, Hennegriff M, Haaf A, Landwehrmeyer G B, Feuerstein T J, Jackisch R
Institut für Pharmakologie und Toxikologie der Universität Freiburg, Neuropharmakologisches Labor, Freiburg, Germany.
Naunyn Schmiedebergs Arch Pharmacol. 2000 Jul;362(1):32-40. doi: 10.1007/s002100000253.
Presynaptic opioid receptors of the delta- and mu-types have been shown to inhibit the release of acetylcholine (ACh) in the rat striatum and hippocampus, respectively, but it is unknown whether opioid receptors modulate the release of ACh also in the region of origin of the hippocampal cholinergic innervation, the septum. To answer this question, slices (350 microm) of the medial septal area and of the diagonal band of Broca, as well as (for comparison) of the hippocampus, were prepared from adult male Wistar rats. The slices were incubated with [3H]choline, superfused in the presence of hemicholinium-3 (10 microM) and stimulated twice (S1, S2) by electrical fields (360 pulses, 3 Hz, 2 ms, 60 mA); opioid receptor agonists were present during S2. The preferential mu-agonist [D-Ala2,N-Me-Phe4,Gly-ol5]enkephalin (DAMGO) inhibited the evoked ACh release by maximally about 40% in hippocampal slices and acted even more strongly in the medial septal area, or the diagonal band of Broca (about 60% or 75% maximal inhibition, respectively). These effects were reduced or abolished by the preferential mu-antagonist naloxone, which showed no effects when given alone. Using naloxone in the presence of a cocktail of peptidase inhibitors, no evidence for an endogenous tone of opioid peptides was found in the medial septal area, diagonal band of Broca or the hippocampus. Using the preferential delta-agonist [D-Pen2, D-Pen5]enkephalin (DPDPE) and the delta-antagonist naltrindole, a delta-opioid receptor inhibiting evoked ACh release was clearly detectable both in the medial septal area and the diagonal band of Broca, but not in the hippocampus, whereas the preferential kappa-agonist trans-3,4-dichloro-N-methyl-N-[2(1-pyrrolidinyl)cyclo-hexyl] benzeneacetamide (U50,488H) had only weak or no effects. In addition to the functional experiments, double in-situ hybridization studies were performed, in which cells containing mRNA for choline acetyltransferase (ChAT) were labeled by an antibody-linked enzymatic staining procedure, whereas mRNAs for mu- or delta-opioid receptors were detected with radioactive probes. These experiments revealed that in the septal region mainly mu-opioid receptors were expressed by neurons positive for ChAT mRNA, whereas in the rat striatum the expression of delta-opioid receptors prevailed in those neurons. We conclude that in the septal area of the rat brain, in contrast to the rat striatum and hippocampus, both presynaptic mu- and delta-opioid receptors modulate the evoked release of ACh. Whether presynaptic mu- and delta-opioid receptors occur on the same or on different septal cells or axon terminals remains to be clarified.
已表明δ型和μ型突触前阿片受体分别抑制大鼠纹状体和海马中乙酰胆碱（ACh）的释放，但尚不清楚阿片受体是否也在海马胆碱能神经支配的起源区域即隔区调节ACh的释放。为回答这个问题，从成年雄性Wistar大鼠制备了内侧隔区、布罗卡斜角带以及（作为对照）海马的切片（350微米）。将切片与[3H]胆碱一起孵育，在3-己基氯化物（10微摩尔）存在下进行灌流，并通过电场（360个脉冲，3赫兹，2毫秒，60毫安）刺激两次（S1、S2）；在S2期间存在阿片受体激动剂。优先的μ激动剂[D-丙氨酸2，N-甲基苯丙氨酸4，甘醇5]脑啡肽（DAMGO）在海马切片中最大程度地抑制诱发的ACh释放约40%，在内侧隔区或布罗卡斜角带中作用更强（分别为最大抑制约60%或75%）。这些作用被优先的μ拮抗剂纳洛酮减弱或消除，单独给予纳洛酮时无作用。在肽酶抑制剂混合物存在下使用纳洛酮，在内侧隔区、布罗卡斜角带或海马中未发现阿片肽内源性张力的证据。使用优先的δ激动剂[D-青霉胺2，D-青霉胺5]脑啡肽（DPDPE）和δ拮抗剂纳曲吲哚，在内侧隔区和布罗卡斜角带中均清晰检测到δ阿片受体抑制诱发的ACh释放，但在海马中未检测到，而优先的κ激动剂反式-3,4-二氯-N-甲基-N-[2-(1-吡咯烷基)环己基]苯乙酰胺（U50,488H）只有微弱作用或无作用。除功能实验外，还进行了双重原位杂交研究，其中通过抗体连接酶染色程序标记含有胆碱乙酰转移酶（ChAT）mRNA的细胞，而用放射性探针检测μ或δ阿片受体的mRNA。这些实验表明，在隔区主要是表达ChAT mRNA的神经元表达μ阿片受体，而在大鼠纹状体中，δ阿片受体在这些神经元中的表达占优势。我们得出结论，在大鼠脑的隔区，与大鼠纹状体和海马不同，突触前μ和δ阿片受体均调节诱发的ACh释放。突触前μ和δ阿片受体是存在于相同还是不同的隔区细胞或轴突终末尚有待阐明。
