Repeated administration of pergolide to rats attenuates the acute elevation of serum corticosterone by pergolide.
A single injection (0.3 mg/kg IP) of pergolide mesylate, a dopamine agonist, increased serum corticosterone concentration several-fold in rats. This increase did not occur or was greatly diminished in rats that had received four previous daily injections of pergolide. The non-responsiveness to pergolide persisted at the second day after the last of 4 daily injections of pergolide, but by the third and fourth days the rats were again responsive to pergolide in terms of serum corticosterone elevation. The lowering of dopamine metabolites (3,4-dihydroxyphenylacetic acid and homovanillic acid) by pergolide occurred in pergolide-pretreated rats to the same extent as in control rats. Serum corticosterone concentration in pergolide-pretreated rats was elevated normally by a serotonin agonist, quipazine. Since the pituitary-adrenocortical system can be activated in pergolide-pretreated rats (indicated by the normal response to quipazine), the insensitivity to pergolide may be due to decreased responsiveness of central dopamine receptors mediating corticosterone elevation by pergolide.
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000187:drug effects; D003345:Corticosterone / Q000097:blood*; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004873:Ergolines / Q000494:pharmacology*; D006719:Homovanillic Acid / Q000378:metabolism; D008297:Male; D010479:Pergolide; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects
D004873:Ergolines; D011954:Receptors, Dopamine; D015102:3,4-Dihydroxyphenylacetic Acid; D010479:Pergolide; D004298:Dopamine; D003345:Corticosterone; D006719:Homovanillic Acid