Characterization of hypotensive and vasorelaxant effects of PHAR-DBH-Me a new cannabinoid receptor agonist.

The effect of PHAR-DBH-Me, a cannabinoid receptor agonist, on different cardiovascular responses in adult male rats was analyzed. The blood pressure was measured directly and indirectly. The coronary flow was measured by Langendorff preparation, and vasomotor responses induced by PHAR-DBH-Me in aortic rings precontracted with phenylephrine (PHEN) were analyzed. The intravenous injection of the compound PHAR-DBH-Me (0.018-185 µg/kg) resulted in decreased blood pressure; maximum effect was observed at the dose of 1,850 µg/kg. A concentration-dependent increase in the coronary flow was observed in a Langendorff preparation. In the aortic rings, with and without endothelium, pre-contracted with PHEN (10-6 M), the addition of PHAR-DBH-Me to the superfusion solution (10-12-10-5 M), produced a vasodilator response, which depends on the concentration and presence of the endothelium. L-NAME inhibited these effects. Addition of CB1 receptor antagonist (AM 251) did not modify the response, while CB2 receptor antagonist (AM630) decreased the potency of relaxation elicited by PHAR-DBH-Me. Indomethacin shifted the curve concentration-response to the left and produced an increase in the magnitude of the maximum endothelium dependent response to this compound. The maximum effect of PHAR-DBH-Me was observed with the concentration of 10-5 M. These results show that PHAR-DBH-Me has a concentration-dependent and endothelium-dependent vasodilator effect through CB2 receptor. This vasodilation is probably mediated by the synthesis/release of NO. On the other hand, it is suggested that PHAR-DBH-Me also induces the release of a vasoconstrictor prostanoid.

Androgens Mediate ß-adrenergic Vasorelaxation Impairment Using Adenylyl Cyclase.

Cardiovascular disease development has been associated with sex differences, suggesting that sex hormones are implicated in vascular function and development of hypertension. Vascular tone comparison at different stages of rat growth represents a good model to study testosterone-related vascular response. We explored the role of testosterone in modulation of age-dependent impaired ß-adrenergic vasodilation. The 3-week-old male Sprague-Dawley rats were sorted in 3-week-old rats without any manipulation and 3-week-old rats treated with testosterone. The 9-week-old rats were randomly grouped into 9-week-old rats without any manipulation (sham), 9-week-old rats that underwent gonadectomy (9-week-old castrated), and 9-week-old castrated treated with testosterone replacement therapy (9-week-old castrated + testosterone). Vascular relaxation was evaluated in aortic rings. ß-adrenergic receptor protein expression, cyclic adenosine monophosphate production, testosterone levels, and adenylyl cyclase (AC) gene expression were assessed. Testosterone levels were low in 3-week-old and 9-week-old castrated rats compared with 9-week-old sham rats. Testosterone replacement raised these levels in 3-week-old and 9-week-old castrated rats similar to those of 9-week-old sham rats. SQ22536, the AC inhibitor, prevented isoproterenol-induced relaxation in aortic rings from 3-week-old and 9-week-old castrated rats. The ß-adrenergic receptor protein expression was similar in all experimental groups. AC mRNA and protein expression and cyclic adenosine monophosphate levels were elevated in 3-week-old and 9-week-old castrated rats compared with 3-week-old + testosterone, 9-week-old sham, and 9-week-old castrated + testosterone rats. In conclusion, we demonstrated that age maturation was associated with vascular relaxation impairment. Variations in testosterone levels and reduced AC expression may be responsible for this altered vascular function.

Pharmacological characterization of mechanisms involved in the vasorelaxation produced by rosuvastatin in aortic rings from rats with a cafeteria-style diet.

The present study aimed to investigate the possible influence of several inhibitors and blockers on the vascular effect produced by the acute in vitro application of rosuvastatin to phenylephrine-precontracted aortic rings from rats with a semi-solid, cafeteria-style (CAF) diet. It also aimed to examine the effects of rosuvastatin on the expression of endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase, constitutive cyclooxygenase, and inducible cyclooxygenase in aortic rings from rats with a CAF diet. From comparisons of the effect on phenylephrine-precontracted aortic rings extracted from rats with two different diets (a standard and a CAF diet), it was found that 10(-9) -10(-5) -mol/L rosuvastatin produced lower concentration-dependent vasorelaxation on rings from the CAF diet group. The vasorelaxant effect was unaffected by the vehicle, but it was significantly attenuated by 10(-5) -mol/L N(G) -nitro-l-arginine methyl ester, 10(-2) -mol/L tetraethylammonium, 10(-3) -mol/L 4-aminopyridine, 10(-7) -mol/L apamin plus 10(-7) -mol/L charybdotoxin, 10(-5) -mol/L indomethacin, or 10(-5) -mol/L cycloheximide. Moreover, in aortic rings from rats with a CAF diet, rosuvastatin enhanced the expression of eNOS, inducible nitric oxide synthase, constitutive cyclooxygenase, and inducible cyclooxygenase. The acute in vitro application of rosuvastatin to phenylephrine-precontracted aortic rings from rats with a CAF diet had a vasorelaxant effect. Overall, the present results suggest that the stimulation of eNOS, the opening of Ca(2+) -activated and voltage-activated K(+) channels, the stimulation of prostaglandin synthesis and enhanced protein levels of eNOS, inducible nitric oxide synthase, constitutive cyclooxygenase, and inducible cyclooxygenase are involved in this relaxant effect.

Age-related differences in the beta-adrenergic vasodilator response in rat aortic rings.

Mechanisms underlying age-dependent changes in vasodilator responses to beta-adrenergic drugs are poorly understood. The aim of the current study was to compare responses to isoproterenol (a non-selective beta-adrenergic receptor agonist) in phenylephrine or KCl precontracted aortic rings from 3 week and 3 month old male Wistar rats. Both the mechanism and the subtype of beta-adrenergic receptor underlying the response to isoproterenol in the both age groups were examined. Endothelial removal, pre-contraction with KCl (40 mM), pre-treatment with tetraethylammonium or with N(omega)-Nitro-L-arginine methyl ester inhibited the vasodilator response to isoproterenol only in aortic rings from older rats. The inhibition was total when TEA and L-NAME were administered together. In both age groups the response to isoproterenol was unaffected by the beta1-adrenergic antagonist CGP20712A, but was significantly inhibited by ICI 118551 (a beta2-adrenergic-antagonist) and to a greater extent by SR 59230A (a non-selective beta 3-adrenergic antagonist), the inhibition being more evident in the older rats. Unlike younger rats, in older animals the response to isoproterenol was partially dependent on endothelial nitric oxide and on K+ channels. In both age groups, beta2- and beta3-, but not beta1-adrenergic receptors were involved. The degree of relative participation of beta2 and beta3 adrenergic receptors may change with age and explain the differences in response to isoproterenol.