Effects of pergolide on dogs with neurogenic hypertension

In pentobarbital anaesthetized dogs with decentralized adrenal glands, sinoaortic baroreceptor deafferentation produced an increase in mean aortic blood pressure which reached a maximum (42 ± 5 mmHg, n=6) within 5 min and then warred entirely within the subsequent 25 min. In contrast, in sham-operated dogs, the maximal pressor response due to the deafferentation was of greater magnitude (63 ± 3 mmHg, n=8) and of much longer duration (44 ± 4 mmHg, 60 min after deafferentation). A marked elevation of epinephrine plasma concentration occurred 5 min after deafferentation and the magnitude of this effect was 8 times greater in dogs with innervated than denervated adrenal glands. In dogs with adrenal glands denervated, pergolide blocked entirely the pressor response and the small elevation in plasma concentration of catecholamines evoked by sinoaortic deafferentation. However, in sham-operated dogs (intact adrenal innervation), pergolide reduced partially the increase in blood pressure and plasma epinephrine concentration caused by deafferentation. In conclusion, the effect of pergolide was mediated by DA-2 dopamine receptors inasmuch as it was prevented by pretreating the dogs with sulpiride, an antagonist of DA-2 dopamine receptors.