Simonic(1988) have investigated that hypothermic effect of oholinornimetics is mediated through an activation of muscarine cholinergic receptors. And also, Yamada(1987) injected trytamine into the lateral cerebroventricle in mice and observed hypothermic through 5-HT1 receptor.
We have previously reported that PCPA(a serotonin depletor), has reduced 5-HT contents gradually, but had a marked reduction in Ach contents in the cortex and hippocampus.
After injection of PCPA and 5,7-DHT, a serotonergic toxin into the cerebroventricle in rats, we observed the colonic body temperature and Ach contents of cerebral cortex.
The results of our study are as follows :
1) Ach contents in the cortex were decreased significantly on the 3rd day & 7th day after PCPA i.c.v. injection.
2) Ach contents in the cortex were not changed on the 3rd day & 7th day after 5,7-DHT i.c.v. injection.
3) Increase in colonic body temperature was markedly observed in rats on 3rd day & 7th day after received intracerebral PCPA injection. During handling with rectal probe insertion there is a small changes of colonic body temperature with time.
4) Increase in colonic body temperature was observed in rats on 3rd day after received intracerebral 5,7-DHT injection. During handling with rectal probe insertion there is a small changes of colonic body temperature with time.
So, we concluded that serotonin depletion could cause a decrease in Ach contents of the cortex and also increase in colonic body temperature via cholinergic system in the brain.
