The effect of sphenopalatine postganglionic neurotomy on the alteration of local cerebral blood flow of normotensive and hypertensive rats in acute cold stress.

The cold season of a year has been reported to have the highest incidence of strokes. Present studies were designed to test whether the parasympathetic denervation plays any role in the regulation of local cerebral blood flow (LCBF) in anesthetized animals exposed to a cold environment. Each species of Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) was divided into four groups: sphenopalatine postganglionic neurotomy (SPNx) or a control group at room temperature (20 degrees C) or in a cold environment (5 degrees C), respectively. LCBF in 14 brain structures was measured using the [14C] iodoantipyrine technique and tissue dissecting methods. Our results show that SPNx did not significantly alter physiological parameters and LCBF in WKY and SHR kept at either 20 degrees C or 5 degrees C. However, 30 minutes of cold exposure caused a significant decrease in the core body temperature of both the WKY and SHR groups (P < 0.05, Student's paired t-test) and a significant decrease in LCBF in 3 of 14 brain areas: the temporal cortex (TC), inferior colliculus (IC) and vermis (VER) of both WKY and SHR (P < 0.05, MANOVA). The percentages of decrease were 24% (TC), 12% (IC), 12% (VER) and 19% (TC), 16% (IC), 15% (VER), respectively. Our findings indicate that in a cold environment, the lower LCBFs in some areas of the brain may be related to decreased body temperature. Whether they are related to the higher prevalence of stroke in winter needs further investigation.