C-FIBER-EVOKED AUTONOMIC CARDIOVASCULAR EFFECTS AFTER INJECTION OF PIPER BETLE INFLORESCENCE EXTRACTS

Piper betle inflorescence extracts contain eugenol (6.2%) and safrole (78.9%). Intravenous injections of water extracts of P. betle inflores cence (PBE), eugenol, and safrole in rats induced hypotensive and brad ycardiac effects, whereas both intraarterial and intrathecal injection s of PEE, eugenol and safrole resulted in hypotensive and tachycardiac effects. Moreover, the effects of intravenous injections of PEE were reversed or inhibited by the pretreatment with bilateral vagotomy, atr opine (1 mg/kg, i.p.) and capsaicin (100 mg/kg, s.c.). Effects of intr aarterial injections of PEE on blood pressure were inhibited by the pr etreatment with substance P (SP) antagonist (1 nmol, i.t.) and clonidi ne (2.5 mu g, i.t.), while heart rate was only inhibited by the pretre atment with SP antagonist (1 nmol, i.t.). In addition, the tachycardia resulting from intrathecal injections of PEE was inhibited by pretrea tment with propranolol (0.3 mg/kg, i.v.). Eugenol and safrole induced the same pattern on blood pressure and heart rate changes as PEE in ra ts after various treatments. This report suggests that acute administr ation of betel inflorescence extracts by different routes may activate C-fiber-evoked parasympathetic and sympathetic cardiovascular reflexe s in rats.