Effects of norepinephrine on alpha-subtype receptors in the feline pulmonary vascular bed.
OBJECTIVE
To test the hypothesis that norepinephrine induces a pressor response in the pulmonary vascular bed of the cat and identify the alpha-(1)adrenoceptor subtypes involved in the mediation or modulation of these effects.


METHODS
Prospective vehicle controlled study.


METHODS
University research laboratory.


METHODS
Intact chest preparation, adult mongrel cats.


METHODS
In separate experiments, the effects of 5-methyl-urapidil, a selective alpha-(1)A-subtype adrenoceptor antagonist, chloroethylclonidine, an alpha-(1)B-subtype and -(1)D-subtype adrenoceptor antagonist, and BMY 7378, the selective alpha-(1)D-subtype adrenoceptor antagonist, were investigated on pulmonary arterial responses to norepinephrine and other agonists in the pulmonary vascular bed of the cat.


RESULTS
The systemic pressure and lobar arterial perfusion pressure were continuously monitored, electronically averaged, and permanently recorded. In the feline pulmonary vascular bed of the isolated left lower lobe, norepinephrine induced a dose-dependent vasoconstrictor response that was not significantly altered after administration of BMY 7378. However, the responses to norepinephrine were significantly attenuated following administration of 5-methyl-urapidil and chloroethylclonidine.


CONCLUSIONS
The results of the present study suggest that norepinephrine has potent vasopressor activity in the pulmonary vascular bed of the cat and that this response may be mediated or modulated by both alpha-(1)A-subtype and -(1)B-subtype adrenoceptor sensitive pathways.
Kaye
Alan D
AD
Department of Anesthesiology, Texas Tech University Health Sciences Center, Lubbock, TX, USA.
Hoover
Jason M
JM
Baber
Syed R
SR
Ibrahim
Ikhlass N
IN
Fields
Aaron M
AM
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002415:Cats; D003000:Clonidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004336:Drug Antagonism; D004353:Drug Evaluation, Preclinical; D004809:Ephedrine / Q000494:pharmacology; D005260:Female; D007269:Injections, Intra-Arterial; D007275:Injections, Intravenous; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology*; D010656:Phenylephrine / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects*; D011652:Pulmonary Circulation / Q000187:drug effects*; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects* / Q000502:physiology; D014655:Vascular Resistance / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D010879:Piperazines; D018340:Receptors, Adrenergic, alpha-1; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; C057446:5-methylurapidil; D010656:Phenylephrine; C051731:chlorethylclonidine; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D004809:Ephedrine; C053428:BMY 7378; D003000:Clonidine; D009638:Norepinephrine