Small changes in heart rate following alpha-1 adrenoceptor stimulation in the anaesthetized dog.
In a previous work (1) we observed a weak alpha-1 adrenoceptor mediated chronotropic effect in anaesthetized dogs: the intracoronary injection of 100 micrograms of amidephrine, an alpha-1 agonist, increased heart rate by 2.5 +/- 0.8 bpm (mean +/- SEM). Since these experiments had been performed in the presence of alpha-2 blockade with yohimbine, one could argue that alpha-1 adrenoceptors had been partially blocked as well. To test for this possibility 5 additional experiments were performed with the same protocol, just omitting yohimbine administration. The chronotropic effect of amidephrine was larger (6.2 +/- 1.9 bpm after i.c. injection of 100 micrograms), but the difference was not significant. This confirms our earlier finding that alpha-1 adrenoceptors are not involved in heart rate control of the anaesthetized dog.
Verlato
G
G
Institute of Human Physiology, University of Verona, Italy.
Borgdorff
P
P
Poltronieri
R
R
D000818:Animals; D004285:Dogs; D004983:Ethanolamines / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
D004983:Ethanolamines; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; C016980:amidephrine