Hajós M, Sharp T
Department of Clinical Pharmacology, Oxford University, Radcliffe Infirmary, UK.
Brain Res. 1996 Nov 18;740(1-2):162-8. doi: 10.1016/s0006-8993(96)00869-4.
We recently reported raphe neurones which frequently fired spikes in short bursts. However, the action potentials were broad and the neurones fired in a slow and regular pattern, suggesting they were an unusual type of 5-hydroxytryptamine (5-HT) neurone. In the present study, we investigated whether these putative burst-firing 5-HT neurones project to the forebrain and whether all spikes fired in bursts propagate along the axon. In anaesthetised rats, electrical stimulation of the medial forebrain bundle evoked antidromic spikes in both burst-firing neurones and in single-spiking, classical 5-HT neurones recorded in the dorsal raphe nucleus. Although the antidromic spike latency of the single-spiking and burst-firing neurones showed a clear overlap, burst-firing neurones had a significantly shorter latency than single-spiking neurones. For both burst-firing neurones and classical 5-HT neurones, antidromic spikes made collisions with spontaneously occurring spikes. Furthermore, in all burst-firing neurones tested, first, second and third order spikes in a burst could be made to collide with antidromic spike. Interestingly, in a small number of burst-firing neurones, antidromic stimulation evoked spike doublets, similar to those recorded spontaneously. From these data we conclude that burst-firing neurones in the dorsal raphe nucleus project to the forebrain, and each spike generated by the burst propagates along the axon and could thereby release transmitter (5-HT).
我们最近报道了中缝神经元，它们经常在短串中频繁发放动作电位。然而，动作电位很宽，且神经元以缓慢且规律的模式发放，这表明它们是一种不寻常类型的5-羟色胺（5-HT）神经元。在本研究中，我们调查了这些假定的爆发式放电5-HT神经元是否投射到前脑，以及爆发式发放的所有动作电位是否都沿轴突传播。在麻醉大鼠中，电刺激内侧前脑束在爆发式放电神经元以及在中缝背核中记录到的单发放、经典5-HT神经元中均诱发了逆向动作电位。虽然单发放和爆发式放电神经元的逆向动作电位潜伏期有明显重叠，但爆发式放电神经元的潜伏期明显短于单发放神经元。对于爆发式放电神经元和经典5-HT神经元，逆向动作电位都与自发产生的动作电位发生了碰撞。此外，在所有测试的爆发式放电神经元中，爆发中的第一、第二和第三个动作电位都可能与逆向动作电位发生碰撞。有趣的是，在少数爆发式放电神经元中，逆向刺激诱发了双脉冲，类似于自发记录到的双脉冲。从这些数据我们得出结论，中缝背核中的爆发式放电神经元投射到前脑，并且爆发产生的每个动作电位都沿轴突传播，从而可能释放递质（5-HT）。
