Mechanisms of acute hypertension and bradycardia following intracisternal 6-hydroxydopamine in conscious rabbits.
Intracisternal (i.c.) 6-hydroxydopamine (6-OHDA) 600 microgram x kg-1 produced a rise in blood pressure and a fall in heart rate, maximal 2-3 h injection. Pretreatment with phentolamine (0.2 or 0.5 mg x kg-1 i.c.) prevented the bradycardia and produced dose-related attenuation of the pressor response. The same dose given 2.1 h after 6-OHDA again abolished the bradycardia but attenuated the pressor response only slightly. We conclude that normally after 6-OHDA both hypertension and bradycardia are due to release of noradrenaline, stimulating alpha-adrenoceptors at distinctive sites in the CNS. The pathway mediating hypertensionis less accessible to the action of phentolamine than that mediating bradycardia.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002946:Cisterna Magna; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006892:Hydroxydopamines / Q000008:administration & dosage / Q000494:pharmacology*; D007267:Injections; D008297:Male; D010646:Phentolamine / Q000494:pharmacology; D011817:Rabbits; D013997:Time Factors
D006892:Hydroxydopamines; D010646:Phentolamine