Involvement of central β-adrenergic, NMDA and thromboxane A receptors in the pressor effect of anandamide in rats

Intravenous (i.v.) injection of the endocannabinoid anandamide induces triphasic cardiovascular responses, including a pressor effect mediated via unknown central and peripheral mechanism(s). The aim of the present study was to determine the central mechanism(s) responsible for the pressor response to anandamide. For this purpose, the influence of antagonists at thromboxane A TP (sulotroban, daltroban, SQ 29548), NMDA (MK-801) and β-adrenergic receptors (ICI 118551) on the pressor effect induced by i.v. and intracerebroventricularly (i.c.v.) administered anandamide was examined in urethane-anaesthetized rats. Anandamide (1.5-3 μmol/kg, i.v.) or its stable analogue methanandamide (0.75 μmol/kg, i.v.) increased blood pressure by 25%. Anandamide (0.03 μmol per animal i.c.v.) caused a pure pressor effect (by 20%) but only in the presence of antagonists of CB and TRPV1 receptors. The effects of cannabinoids (i.v. or i.c.v.) were diminished by i.v. daltroban, sulotroban (10 μmol/kg each), and/or SQ 29548 (1 μmol/kg). The effect of anandamide i.v. was reduced by SQ 29548 (0.02 μmol per animal i.c.v.) and by the thromboxane A synthesis inhibitor furegrelate i.c.v. (1.8 μmol per animal). ICI 118551, MK-801 (1 μmol/kg i.v. each), and bilateral adrenalectomy diminished the effect of anandamide i.c.v. Sulotroban (i.v.) failed to affect the response to anandamide (i.v.) in pithed rats, and anandamide and methanandamide did not bind to TP receptors in rat platelets. The present study suggests that central β-adrenergic, NMDA and thromboxane A receptors are involved in the anandamide-induced adrenal secretion of catecholamines and their pressor effect in urethane-anaesthetized rats. © 2010 Springer-Verlag.