Effects of fentanyl on a bradykinin-induced excitatory cardiac reflex in the anaesthetized rat.
A reflex increase in arterial blood pressure and heart rate was elicited by application of epicardial bradykinin (4 X 10(-8), 2 X 10(-7), 10(-6) g/ml) in pentobarbital-anaesthetized, thoracotomized rats. The influence of the opioid fentanyl and the tranquilizer diazepam on this increase was then investigated. When fentanyl (2.2 micrograms/(kg X min] was infused i.v. during periods of bradykinin application, a highly significant suppression of the excitatory reflex resulted. Epicardial bradykinin (10(-6) g/ml) induced an increase in mean arterial blood pressure of 25.3 +/- 3.5 mm Hg during the control period and of 6.8 +/- 1.4 mm Hg during fentanyl infusion. The corresponding changes in heart rate were +20.8 +/- 4.7 beats/min during the control period and +1.9 +/- 1.3 beats/min during fentanyl infusion. When cardioacceleration was induced by the carotid occlusion reflex, fentanyl antagonized this effect too. The effect of fentanyl was entirely neutralized by injecting naloxone (30 micrograms/kg i.v.) prior to application of the former. Diazepam had no influence on the bradykinin-induced reflex. The results support the view that morphinoceptors may modulate the excitatory cardiac reflex induced by epicardial application of the algesic bradykinin in the rat.
D000758:Anesthesia; D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D001920:Bradykinin / Q000494:pharmacology*; D003975:Diazepam / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005283:Fentanyl / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012018:Reflex / Q000187:drug effects*
D003975:Diazepam; D001920:Bradykinin; D005283:Fentanyl