Horrigan D J, Horwitz B A, Horowitz J M
Section of Neurobiology, Physiology, and Behavior, University of California, Davis 95616, USA.
Am J Physiol. 1997 Oct;273(4 Pt 2):R1291-8. doi: 10.1152/ajpregu.1997.273.4.r1291.
Serotonergic fibers project to the hippocampus, a brain area previously shown to have distinctive changes in electroencephalograph (EEG) activity during entrance into and arousal from hibernation. The EEG activity is generated by pyramidal cells in both hibernating and nonhibernating species. Using the brain slice preparation, we characterized serotonergic responses of these CA1 pyramidal cells in euthermic, cold-acclimated, and hibernating Syrian hamsters. Stimulation of Shaffer-collateral/commissural fibers evoked fast synaptic excitation of CA1 pyramidal cells, a response monitored by recording population spikes (the synchronous generation of action potentials). Neuromodulation by serotonin (5-HT) decreased population spike amplitude by 54% in cold-acclimated animals, 80% in hibernating hamsters, and 63% in euthermic animals. The depression was significantly greater in slices from hibernators than from cold-acclimated animals. In slices from euthermic animals, changes in extracellular K+ concentration between 2.5 and 5.0 mM did not significantly alter serotonergic responses. The 5-HT1A agonist 8-hydroxy-2(di-n-propylamino)tetralin mimicked serotonergic inhibition in euthermic hamsters. Results show that 5-HT is a robust neuromodulator not only in euthermic animals but also in cold-acclimated and hibernating hamsters.
血清素能纤维投射到海马体，海马体是一个之前已被证明在进入冬眠和从冬眠中苏醒时脑电图（EEG）活动会发生显著变化的脑区。EEG活动由冬眠和非冬眠物种的锥体细胞产生。利用脑片制备技术，我们对正常体温、冷适应和冬眠的叙利亚仓鼠中这些CA1锥体细胞的血清素能反应进行了表征。刺激海马联合纤维会诱发CA1锥体细胞的快速突触兴奋，这种反应通过记录群体峰电位（动作电位的同步产生）来监测。血清素（5-HT）的神经调节作用使冷适应动物的群体峰电位幅度降低了54%，冬眠仓鼠降低了80%，正常体温动物降低了63%。冬眠动物脑片的抑制作用明显大于冷适应动物的脑片。在正常体温动物的脑片中，细胞外钾离子浓度在2.5至5.0 mM之间的变化并未显著改变血清素能反应。5-HT1A激动剂8-羟基-2-（二正丙基氨基）四氢萘在正常体温的仓鼠中模拟了血清素能抑制作用。结果表明，5-HT不仅在正常体温动物中是一种强大的神经调节剂，在冷适应和冬眠的仓鼠中也是如此。
