Effect of co-dergocrine in the autoperfused superior mesenteric vascular bed of the rat.
1. The influence of local administration of co-dergocrine in the in situ, constant flow autoperfused, superior mesenteric vascular bed of the rat was investigated. 2. Local infusion of co-dergocrine (0.1 micrograms kg-1 min-1) reduced the pressor response to electrical stimulation of the periarterial sympathetic nerves for the whole frequency range studied during cumulative frequency-response curves (1-8 Hz). 3. Co-dergocrine (0.01, 0.03, 0.1 micrograms kg-1 min-1) dose-dependently inhibited the pressor response to electrical stimulation at 4 Hz; increases in perfusion pressure produced by locally administered noradrenaline were inhibited to the same degree. 4. Pressor responses induced by locally administered phenylephrine were also inhibited by co-dergocrine (0.1 micrograms kg-1 min-1) while those produced by local injection of angiotensin II were not. 5. Local administration of the DA1-/DA2-receptor antagonist haloperidol (1 microgram kg-1), the DA2-receptor antagonist domperidone (10 micrograms kg-1) and the alpha 2-adrenoceptor antagonist rauwolscine (100 micrograms kg-1) partially prevented the influence of co-dergocrine on the electrically induced response. 6. The results show that the effect of co-dergocrine in the rat superior mesenteric vascular bed cannot simply be ascribed to interaction with the presynaptic inhibitory DA2-receptors on the noradrenergic nerve endings; it also has an antagonistic action at the postsynaptic alpha 1-adrenoceptors and an agonist action at the presynaptic alpha 2-adrenoceptors.
Lefebvre
R A
RA
Heymans Institute of Pharmacology, University of Gent Medical School, Belgium.
Devreese
K
K
D000804:Angiotensin II / Q000037:antagonists & inhibitors; D000818:Animals; D004088:Dihydroergotoxine / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004294:Domperidone / Q000494:pharmacology; D005260:Female; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D008642:Mesenteric Veins / Q000187:drug effects*; D009638:Norepinephrine / Q000037:antagonists & inhibitors; D010477:Perfusion / Q000379:methods; D010656:Phenylephrine / Q000037:antagonists & inhibitors; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D004088:Dihydroergotoxine; D000804:Angiotensin II; D010656:Phenylephrine; D015016:Yohimbine; D004294:Domperidone; D006220:Haloperidol; D009638:Norepinephrine