Effects of oolong tea on renal sympathetic nerve activity and spontaneous hypertension in rats.

In a previous study, evidence was presented that oolong tea (OT) reduced abdominal fat accumulation in diet-induced obese mice. In the study presented here, we examined the sympathetic and cardiovascular effects of intraduodenal injection of OT in urethane-anesthetized rats and found that it suppressed renal sympathetic nerve activity (RSNA) and blood pressure (BP). In addition, pretreatment with the histaminergic H3-receptor antagonist thioperamide or bilateral subdiaphragmatic vagotomy eliminated the effects of OT on RSNA and BP. Furthermore, OT drinking for 14 weeks reduced BP elevation in spontaneously hypertensive rats. These results thus suggest that OT may exert its hypotensive action through changes in autonomic neurotransmission via an afferent neural mechanism. Moreover, we found that intraduodenal injection of decaffeinated OT lowered RSNA and BP as well as OT, indicating that substances other than caffeine contained in OT may function as effective modulators of RSNA and BP.