Elevation of Serum Corticosterone Concentrations in Rats by Pergolide and Other Dopamine Agonists

Abstract

Pergolide, a dopamine agonist, elevated serum corticosterone concentrations in rats. The elevation was dose dependent, a maximum effect being produced at a dose of 0.3 mg/kg, ip. The serum corticosterone concentration was highest 30–60 min after pergolide injection and had returned to normal by 4 h. Spiperone and haloperidol, known dopamine antagonists, blocked the increase in serum corticosterone. Metergoline and mianserin did not alter the increase in serum corticosterone caused by pergolide, but these serotonin antagonists prevented the increase caused by quipazine, a serotonin agonist. Haloperidol did not influence serum corticosterone elevation by quipazine, but spiperone partially antagonized quipazine's effect atdoses higher than those required to prevent the effect of pergolide (spiperone is known to block some serotonin receptors as well as dopamine receptors). The ED ₅₀ for spiperone in antagonizing serum corticosterone elevation by pergolide was 0.003– 0.01 mg/kg whereas the EDr,o for spiperone in antagonizing serum corticosterone elevation by quipazine was 1–3 mg/kg. Domperidone, which blocks dopamine receptors in the periphery but not in the brain, did not prevent the elevation of serum corticosterone by pergolide. Other direct and indirect dopaminergic agonists (lergotrile, apomorphine, N₃N-dipropyl-2-aminotetralin, amfonelic acid, and L-dopa) also elevated serum corticosterone in rats, but a close structural analog of pergolide, relatively inactive as a dopamine agonist, had little or no effect. These results suggest that activation of pituitary-adrenocortical function occurs in the rat in response to stimulation of central dopamine receptors.