Inhibitory adrenergic control of heart rate of perch (Perca fluviatilis) in vitro.
1. Adrenaline and noradrenaline, but not isoprenaline or phenylephrine, showed a negative chronotropic effect on the isolated perch heart. 2. This adrenergic effect was blocked by an alpha-adrenergic antagonist, phentolamine, but not by a beta-blocker, propranolol, suggesting the role of alpha receptors in this action. 3. When a ligature between the atrium and the ventricle was used, adrenaline inhibited the beating of the atrium but not of the ventricle. This suggests that the negative chronotropic effect occurred in the whole heart through an atrial pacemaker (sinus node). 4. The sensitivity of the heart to the adrenergic effect was temperature-dependent and greater at low test temperature. At 15 degrees C pD2 for noradrenaline was 6.45 +/- 0.20 and for adrenaline 6.33 +/- 0.20. At 24 degrees C the values were 5.44 +/- 0.12 and 5.67 +/- 0.15, respectively.
D000818:Animals; D003864:Depression, Chemical; D004837:Epinephrine / Q000494:pharmacology; D005399:Fishes / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000502:physiology*; D013696:Temperature
D009638:Norepinephrine; D004837:Epinephrine