刺激皮肤诱发的鲫鱼Mauthner细胞复合性兴奋性突触后电位和动作电位

Compound EPSPs and Action Potential of Mauthner Cell Evoked by Skin Stimulation in Crucian Carp

目的研究皮肤感觉传入信息对Mauthner细胞M细胞兴奋性的影响。方法电刺激皮肤并结合M细胞多点胞内穿刺技术记录胞体及腹侧树突的电反应。结果刺激躯干部皮肤在国产鲫鱼M细胞上记录到3组复合性兴奋性突触后电位(EPSP):a组EPSP幅度最低潜伏期和时程也最短,分布在胞体及胞体附近的腹侧树突上,耐受≥1Hz的刺激。b组EPSP幅度最高,时程最长,潜伏期介于a、c两组之间不耐受≥1Hz的刺激从胞体到腹侧树突末梢端幅度逐渐增大;在b组EPSP基础上可爆发动作电位。c组EPSP的特点是需要较强(伤害性)刺激≥100V才可出现,潜伏期最长幅度介于a、b两组之间,不耐受≥1Hz的刺激。上述3组EPSP上均叠加有代表电突触活动的尖峰样瞬变电位。结论(1)皮肤感觉传入信息可使M细胞爆发动作电位,这与以往观点不同;(2)皮肤伤害性刺激可使M细胞产生一个迟发性EPSP(3)从皮肤投射到M细胞的神经通路可能是由含有不同突触接替次数和不同突触种类的神经链群组成,它们在M细胞上的投射部位各异;4在上述通路上有可能皆存在电和化学突触。

Objective To investigate the effects of afferent excitatory inputs from ski n on the excitability of Mauthner cell(M cell)of crucian carp.Methods Multip le-site intracellular recordings on the soma and the ventral dendrite(VD)of M cell and direct current stimulation on the skin surface of the fi-sh' s trunk were employed.Results Direct stimulation of the skin evoked3groups of compoun d exc itatory postsynaptic potentials(EPSPs)on soma and VD of M cell.Group a EPSP had the lowest amplitude(≤0.35mV),which was insensitive to high-fr equency stimulation.It had the shortest latency(mean1.9ms)and could be rec orded on the soma and the proximal end of VD.Group b EPSP had the highest ampl itude(≤9.7mV),which was increased when the recording electrode was moved from the soma to the distal end of VD.The latency of Group b(mean4.5ms)wa s shorter than that of Gro up c,but longer than that of Group a.We firstly f ound that action potential could be induced on the basis of Group b in M cell by skin stimulation.Group c EPSP was our new finding,which could only be evoked by higher intensity(noxious)stimulus(≥100V).It had the longest latency (me -an13.5ms)with amplitude between those of a and b,and was very sensit ive to high frequency stim-ula tion.All the three groups of EPSPs were superim posed with spike-like transient potentials,which were believed to be the sign of electrical synapse activities.Conclusions (1)Action potential can be ind uced on M cell by skin stimulation,which is in controversy with previous report s;(2)the nox ious skin stimulation can induce a late EPSP(Group c)in M cell;(3) the neural pathway projec-ting from skin to M cell is composed of a set of neuro nal chains with different number of synaptic relays,in which short chains proj ected concentrically to the soma and the proximal part of VD,while long chains pro jected mainly to the distal part of VD;(4)both electrical and chemical synapses may exist in short and long pathways.