Peripheral dopaminergic receptors. Physiological and pharmaceutical aspects of therapeutic importance.

Evidence for the existence of dopamine (DA) receptors in structures peripheral to the blood-brain barrier is accumulating. Two important central dopaminergic systems are functionally located peripheral to the blood-brain barrier, viz, the DA receptors in the chemoceptor trigger zone (CTZ) and those in the anterior pituitary. Agonists on these systems induce vomiting and reduce milk production, while antagonists have opposite effects. DA receptors also occur in the proximal gastrointestinal tract where activation of DA receptors delays gastric emptying. DA antagonists, however, enhance gastric emptying and prevent gastro-oesophageal reflux probably via an action on DA receptors in the stomach. DA receptors also occur in renal, mesenteric, coronary and intracerebral arteries. Activation of these DA receptors causes vasodilatation with a resultant increase in regional tissue perfusion.