抄録
We have previously shown that the defense response was attenuated in prepro-orexin gene knockout mice (Am J Physiol, 2003, 285:R581). Because the defense response was not completely abolished in the knockout mice, we have speculated that the co-transmitters contained in the orexinergic neurons may also participate in the defense response. To test the hypothesis, here we used orexin neuron-ablated mice that were generated by introducing a transgene to express a neurotoxin under regulation of the orexin-promoter. In urethane-anesthetized mice, a GABA-A receptor antagonist, bicuculline, was microinjected into the perifornical area in the posterior hypothalamus, so called defense area. Defense response was defined as simultaneous elevation of blood pressure, heart rate, and minute ventilation and shift of blood flow from the visceral to the muscular vasculature. Excitation of the perifornical area by disinhibition with bicuculline resulted in an attenuated defense response in orexin neuron-ablated mice. However, the defense response was still remained about a half magnitude as compared to the wild-type controls as was the case in prepro-orexin knockout mice. We conclude that orexin but not co-transmitters in the orexinergic neurons plays a role as a master switch to elicit multifaceted autonomic and respiratory changes in the defense response. [Jpn J Physiol 55 Suppl:S87 (2005)]
