ROLE OF CAPSAICIN‐SENSITIVE SENSORY NERVES IN MEDIATION OF THE CARDIOVASCULAR EFFECTS OF THE ESSENTIAL OIL OF CROTON ZEHNTNERI LEAVES IN ANAESTHETIZED RATS

Abstract

The essential oil of Croton zehntneri Pax et Hoffm. (EOCZ) contains anethole (42%) and estragole (46%), two isomers that share some chemical structural similarities with capsaicin. The present study investigated the cardiovascular effects of EOCZ and the role of capsaicin-sensitive sensory nerve fibres in the mediation of these effects in anaesthetized rats. 2. Intravenous bolus injection of EOCZ (1-20 mg/kg) elicited dose-dependent hypotension and bradycardia that were immediate and transient. Similar responses were also observed with anethole and estragole (both at 10 mg/kg). After cervical bivagotomy or perineural treatment of both cervical vagus nerves with capsaicin (250 mg/mL) to selectively block the conduction of sensory C-fibres, both cardiovascular responses to EOCZ (10 mg/kg) were abolished. 3. Like capsaicin, an epigastric retrograde intra-arterial injection of EOCZ (10 mg/kg, i.a.) into the femoral artery elicited a monophasic hypotensive response. This reflex response was blocked by either neonatal pretreatment with capsaicin (50 mg/kg, s.c.) or intrathecal injection of the substance P receptor antagonist RP 67580 (7.8 nmol, at the spinal level L5-L6), suggesting that it is mediated exclusively by substance P-containing primary afferent fibres. 4. The cardiovascular responses to EOCZ (10 mg/kg, i.v.) were also significantly reduced by the selective vallinoid TPRV1 receptor antagonist capsazepine (1 mg/kg, i.v.). 5. It is concluded that i.v. administration of EOCZ in anaesthetized rats elicits a capsaicin-like bradycardic and depressor reflex, which appears to be mediated by the activation of vallinoid TPRV1 receptors located on vagal sensory nerves. Like capsaicin, i.a. injection of EOCZ induces a spinally mediated sensory reflex.

Cardiovascular effects of 1-nitro-2-phenylethane, the main constituent of the essential oil of Aniba canelilla, in spontaneously hypertensive rats

“…In four different groups of rats, maximal changes in MAP and HR elicited by i.v. injection of EOAC and NP (both at 10 mg/kg) were determined before and 20 min after a cervical bilateral vagotomy (Series 2; n = 5 and 6, respectively), before and 20 min after bilateral perineural treatment (PNT) with CAP (250 μg/mL; n = 5 and 6, respectively) (Series 3) as previously described [11], before and 2 min after i.v. pretreatment with the competitive TPRV 1 receptor antagonist, capsazepine (1 mg/kg) [12] ( n = 6 and 6, respectively) (Series 4), and before and 5 min after i.v.…”

Cardiovascular Effects of the Essential Oil of Croton argyrophylloides in Normotensive Rats: Role of the Autonomic Nervous System

“…Previously, we reported that EOCA was able to relax both a conduit artery and a resistance vascular bed preparation [8], an effect that could be responsible for a putative hypotensive action of this essential oil, as previously demonstrated for EOCN [9] and EOCZ [13, 14] in normotensive rats. As no information in the international literature is available regarding this hypothesis, the present study was undertaken to test such a possibility and also to elucidate the mechanisms underlying the vasorelaxant effects of EOCA.…”

“…Doses of antagonists and EOCA were chosen according to those recommended in the literature and those employed in our previous investigations [13, 14, 18, 20–23], respectively. In a first series of experiments, a dose-effect relationship was determined in anesthetized rats which have been submitted ( n = 6) or not ( n = 5) to a cervical bilateral vagotomy.…”

Essential oil of Croton zehntneri and its major constituent anethole display gastroprotective effect by increasing the surface mucous layer

“…vagus reflex) and then an increase in blood pressure. Further studies carried out in anesthetized rats showed that EOCZ‐induced capsaicin‐like bradycardic and depressor reflex is mediated through the activation of vanilloid TPRV 1 receptors located on sensory vagal nerves [9]. A hydrolate obtained from stalk and leaves of C. zehntneri contains compounds with larvicidal activity against third instar Aedes aegypti larvae [10], and EOCZ presents antifungal activity against the dermatophytic fungus Microsporum canis [11].…”