Pharmacological evidence that central alpha 2-adrenoceptors are involved in cardiovascular responses to intravenously injected enkephalins in anesthetized dogs.
In anesthetized dogs, intravenous infections of 30 micrograms/kg of leucine- and methionine-enkephalin (L- and M-enk respectively) produced a significant reduction of mean blood pressure (MPB) and heart rate (HR). The peak decreases in MBP and HR occurred within 1 min after injection and recoveries to pre-injection levels within 3 min. The depressor responses to both L-enk and M-enk were abolished by intracisternal pretreatment with yohimbine (0.5 mg/kg) but not with prazosin (0.1 mg/kg). Pretreatment with either drug did not alter the bradycardia. All cardiovascular effects of both L-enk and M-enk were prevented by intravenous pretreatment with naloxone (2 mg/kg). These results suggest that central alpha 2-adrenoceptors may participate in the central actions of enkephalins on blood pressure regulation. HR responses to enkephalins may be elicited by a different mechanism.
D000768:Anesthesia, General; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001933:Brain Stem / Q000502:physiology*; D002319:Cardiovascular System / Q000187:drug effects*; D004285:Dogs; D004743:Enkephalin, Leucine / Q000494:pharmacology*; D004744:Enkephalin, Methionine / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D007267:Injections; D007275:Injections, Intravenous; D011224:Prazosin / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D011224:Prazosin