title: Mechanism of action of phenylephrine on isolated guinea-pig atria rate.
abstract: 1. Phenylephrine has a positive chronotropic effect on the right isolated guinea-pig atria and this effect is not modified by alpha-adrenergic blocker (phentolamine) but it is drastically inhibited by beta-adrenergic antagonists (practolol or propranolol). 2. The effect is substantially reduced by treatment with cocaine or pretreatment with reserpine. 3. Cocaine plus reserpine shift the dose-response curve for phenylephrine to the left. 4. It is concluded that positive chronotropic effect of phenylephrine has two components: direct action on beta-adrenergic receptors and an indirect action due to norepinephrine release.
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D003042:Cocaine / Q000494:pharmacology; D004347:Drug Interactions; D005260:Female; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology*; D012110:Reserpine / Q000494:pharmacology
chemical_list: D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D010656:Phenylephrine; D012110:Reserpine; D003042:Cocaine