Background: Diabetes mellitus is associated with abnormalities in peripheral/central catecholaminergic systems, including changes in catecholamine levels and receptor expression.

Objective: Since quinpirole-induced cardiac sympathetic inhibition is greater in diabetic than in normoglycemic rats, this study pharmacologically investigated the dopamine D -like receptor subtypes that mediate cardiac sympathetic inhibition in diabetic (streptozotocin [STZ]-pretreated) pithed rats.

Methods: Fifty male Wistar rats were pretreated with STZ, pithed and conditioned for spinal stimulation (C -T ) of the tachycardic sympathetic tone. The resulting increases in heart rate were evaluated following i.v. blocking doses of antagonists at D , D and D receptors during a continuous i.v. infusion of quinpirole (an agonist at D -like receptors) or saline (vehicle).

Results: With this experimental approach, the cardiac sympathetic inhibition produced by quinpirole in diabetic rats was: (i) unchanged after administration of vehicles and; (ii) abolished by the antagonists L-741,626 (D ), SB-277011-A (D ) or L-745,870 (D ).

Conclusion: These findings in diabetic pithed rats imply that: (i) the cardiac sympathetic inhibition by quinpirole involves activation of D dopamine receptors; and (ii) there is a differential stimulation of these receptors compared to normoglycemic rats. These D receptor subtypes could be a novel drug target for the therapy of typical cardiac complications of diabetes.

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http://dx.doi.org/10.1111/bcpt.13774DOI Listing

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