Rodríguez-Sosa Leonardo, Calderón-Rosete Gabina, Flores Gonzalo, Porras M G
División de Estudios de Posgrado, Facultad de Medicina, Universidad Nacional Autónoma de México, Av. Universidad No. 3000, Ciudad Universitaria, 04510 Mexico.
Synapse. 2007 Oct;61(10):801-8. doi: 10.1002/syn.20425.
In the sixth abdominal ganglion (sixth AG) of the crayfish, two photosensitive neurons are located and have been identified as caudal photoreceptors (CPRs). We have expanded our investigation on the role of 5-Hydroxytryptamine (5-HT) as a modulator of the spontaneous and light-induced activity of the CPR. We located, by using immunocytochemistry, neurons in the sixth AG that contain the 5HT1A receptor. The expression of these receptors was examined by binding assays with [3H] 8-hydroxy-2 (di-n-propylamino) tetralin ([3H(8-OH-DPAT). We examined the exogenous action of both 5HT and its agonist 8-OH-DPAT on the phase of circadian rhythms of the spontaneous electrical activity and the photoresponse of the CPR in the isolated sixth AG by conventional extracellular recording methods. Experiments were made on the adult crayfish Procambarus clarkii and Cherax quadricarinatus. Thirteen immunopositive neurons were located, principally near the ventral and dorsal surface of the sixth AG, with the mean diameter of their somata 20+/-3 microm. The specific binding data showed the presence of 5-HT1A receptors with a mean level of 22.4+/-6.6 fmol/mg of wet tissue. Spontaneous and light-induced electrical activity of the CPR showed circadian variations with their activity more intense at night than in the day. Exogenous application of 5-HT or 8-OH-DPAT causes a circadian phase-shift in electrical activity of the CPR. Taken together, these results lead us to believe the 5-HT acts as a modulator of circadian electrical activity of the CPR in the isolated sixth AG of crayfish. Moreover, it suggests that the 5-HT1A receptor participates in this modulation.
在小龙虾的第六腹神经节（第六AG）中，发现了两个光敏神经元，并已确定为尾侧光感受器（CPR）。我们扩展了对5-羟色胺（5-HT）作为CPR自发和光诱导活动调节剂作用的研究。我们通过免疫细胞化学方法，在第六AG中定位了含有5HT1A受体的神经元。通过用[3H]8-羟基-2（二正丙基氨基）四氢萘（[3H(8-OH-DPAT)]进行结合试验，检测了这些受体的表达。我们通过传统的细胞外记录方法，研究了5HT及其激动剂8-OH-DPAT对分离的第六AG中CPR自发电活动和光反应的昼夜节律相位的外源作用。实验以成年克氏原螯虾和四脊光壳螯虾为对象。共定位到13个免疫阳性神经元，主要位于第六AG的腹侧和背侧表面附近，其胞体平均直径为20±3微米。特异性结合数据显示存在5-HT1A受体，平均水平为22.4±6.6 fmol/mg湿组织。CPR的自发和光诱导电活动表现出昼夜变化，其活动在夜间比白天更强烈。外源应用5-HT或8-OH-DPAT会导致CPR电活动的昼夜相位偏移。综上所述，这些结果使我们相信5-HT在小龙虾分离的第六AG中作为CPR昼夜电活动的调节剂发挥作用。此外，这表明5-HT1A受体参与了这种调节。
