Cholinergic dopamine release from the in vitro rabbit carotid body.

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Abstract
The aim of this study was to test whether cholinergic mechanisms regulate dopamine (DA) release from the carotid body (CB) and interact with DA D2 autoreceptors. One hundred forty-two CBs from adult rabbits were infused in vitro in a surviving medium bubbled with O2 (Bairam A, Marchal F, Cottet-Emard JM, Basson H, Pequignot JM, Hascoet JM, and Lahiri S. J Appl Physiol 80: 20–24, 1996 ). CB DA content and release were measured after 1 h of exposure to various treatments: control, cholinergic agonist (0.1–50 μM carbachol), full muscarinic antagonist (1 and 10 μM atropine), antagonists of M1 and M2 muscarinic receptors (1 and 10 μM pirenzepine and 10 μM AFDX-116, respectively), and the DA D2 receptor antagonist domperidone (1 μM), alone and with carbachol (1 μM). Compared with control, the release of DA was significantly increased by carbachol (1–50 μM), AFDX-116, and domperidone and decreased by atropine (10 μM) and pirenzepine (10 μM). The effects of domperidone and carbachol were not significantly different but were clearly additive. It is concluded that, in the rabbit CB, M1 and M2 muscarinic receptor subtypes may be involved in the control of DA release, in addition to the DA D2 autoreceptors.