Abstract
We have investigated the characteristics of peripheral orexin system in guinea-pig intestine by means of intracellular recording, Magnus method, Ussing method and fluorescent-immunohistochemistry. This time, enteric orexin system in the rat intestine was investigated to compare with that of guinea-pig, because rats are more commonly used in sleep researches. The guinea-pig intestine indicated twitch contraction after transmural electrical nerve stimulation (duration: 1-3 ms, 5-10 pulses/20 s, 10 Hz, voltage: 40 v), while rat intestine showed weak oscillatory responses to strong electrical stimuli (duration: 10-50 ms, 5-10 pulses/20 s, 10 Hz, voltage: 40 v). Orexin dose-dependently (10-300 nM) augmented the nerve stimulation-induced twitch response in the guinea-pig intestine. On the other hand, orexin dose-dependently increased resting tension of the rat intestine (3-100 nM), without affecting nerve stimulation-induced responses. The actions of orexin A were stronger than that of orexin B in guinea-pig intestine, while orexin B was stronger in the rat intestine. The oral part of rat ileum was more sensitive than the lower part of the ileum. This specie dependency of orexin response may reflect food difference and it may affect the sleep-awake cycle of the animals. [Jpn J Physiol 54 Suppl:S201 (2004)]
