兔肠系膜下神经节细胞的两种非胆碱能性慢突触后电位

以常规细胞内记录技术对兔肠系膜下神经节细胞的跨膜电位进行了观察。对节前神经的短串脉冲刺激,可诱发出一串快兴奋性突触后电位(f-EPSP)或顺向动作电位;在此之后,大多数细胞还出现一个持续约2min 的缓慢去极化电位。该电位具有抗箭毒和阿托品性质,受低钙高镁溶液的可逆性阻抑,因而可称为非胆碱能性兴奋性突触后电位,或者也可归入迟慢兴奋性突触后电位(ls-EPSP)。多数细胞的 ls-EPSP 伴有膜电阻增大,电位的幅度随细胞静息电位的超极化而变小;提示在这些细胞上,钾电导的失活很可能参与了电位的发生。以P物质溶液灌流神经节未见该电位有显著改变。另外,在箭毒化加阿托品化的神经节中,还发现少数细胞对节前神经的串刺激发生一个持续约一分钟的超极化电位。它也具有抗胆碱能受体阻断剂的性质,受低钙高镁溶液可逆性阻抑,为此我们命之为“极慢抑制性突触后电位”(vs-IPSP),以区别于“慢抑制性突触后电位”(s-IPSP),后者是通常用以表示一种胆碱能性的慢电位。本文所述的这两种非胆碱能性的突触电位有关递质,尚待探索。

TWO TYPES OF NON-CHOLINERGIC SLOW POSTSYNAPTIC POTENTIALS IN INFERIOR MESENTERIC GANGLION NEURONS OF THE RABBIT

With a bridge pre-amplifier, the transmembrane potential of the inferior mes-enteric ganglion (IMG) cell of the rabbit was investigated by intracellular record-ing techinque. A short train of stimulation of the pregangionic nerves elicited avolley of fast excitatory postsynaptic potentials or orthodromic discharges whichwere followed, in the majority of cells, by a slow depolarization lasting for about 2min. This slow potential was resistant to d-tubocurarine (d-TC) and atropine,and could be reversibly blocked by a low calcium (0.25 mM) and high magnesium12 mM) Krebs solution; consequently the potential was termed non-cholinergicexcitatory postsynaptic potential and could be categorized as a kind of late slow ex-citatory postsynaptic potential (ls-EPSP). The ls-EPSP in the majority of cellssampled was accompanied by an inrease in membrane resistance and was attenu-ated upon conditioning hyperpolarization, which suggested that an inactivationof potassium conductance was probably involved in genesis of the slow potential.Superfusion of substance P caused no appreciable change in the ls-EPSP. In addi-tion, some of the cells in the rabbit IMG generated a hyperpolarization potentialafter a train stimulation of the preganglionic fibers. The hyperpolarization lastedabout 1 min and was enhanced by conditioning hyperpolarization. It was alsod-TC and atropine resistant, but sensitive to low calcium/high magnesium; there-fore, it was termed "very slow inhibitory postsynaptic potential" (vs-IPSP) to bedistinguished from the s-IPSP, a conventional term for the slow cholinergic synapticresponse in some autonomic neurones. The transmitters responsible for these twotypes of non-cholinergic synaptic potentials remain to be identified.