title: Influence of temperature and frequency on the positive inotropic action of phenylephrine in the isolated rabbit papillary muscle.
abstract: On the isolated papillary muscle of the rabbit the maximal developed tension induced by phenylephrine bia alpha-adrenoceptors was not affected by changing the temperature, while the basal developed tension of the muscle was significantly increased or decreased by lowering the temperature from 37 degrees C to 32 degrees C or by raising it to 42 degrees C, respectively. When the temperature was lowered from 37 degrees C to 32 degrees C in the muscle stimulated at a frequency of 0.5 Hz, the dose-response curve for phenylephrine via alpha-adrenoceptors was shifted to the left (delta pD2-0.47), while that for phenylephrine via beta-adrenoceptors was also shifted to the left to a similar extent (delta pD2=0.43). When the temperature was raised from 37 degrees C to 42 degrees C, the dose-response curve for phenylephrine via alpha-adrenoceptors was markedly shifted to the right (delta pD2=1.58), whereas that via beta-adrenoceptors was not affected at all by this elevation of the temperature (delta pD2=0.04). The change of the stimulation frequency affected chiefly the intrinsic activity of phenylephrine but not the affinity of the drug for alpha-adrenoceptors expressed as the pD2-value.
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D010210:Papillary Muscles / Q000187:drug effects; D010646:Phentolamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology*; D010869:Pindolol / Q000494:pharmacology; D011817:Rabbits; D013268:Stimulation, Chemical; D013696:Temperature
chemical_list: D010656:Phenylephrine; D010869:Pindolol; D010646:Phentolamine