title: Dopamine D2 receptors in the posterior region of the nucleus tractus solitarius mediate the central pressor action of quinpirole (LY171555).
abstract: Our previous studies demonstrated that intravenous (IV) administration of the selective dopamine (DA) D2 receptor agonist quinpirole (LY171555) induces a pressor response in conscious Sprague-Dawley (S-D) rats through a central mechanism. The present study was designed to identify the neurons which medicate this pressor response. Injection of quinpirole (1-150 micrograms/kg) into the 4th ventricle produced a greater pressor response of a more rapid onset than similar injections into the lateral ventricle in conscious, freely moving S-D rats, suggesting a site of action in brainstem. Further, microinjections (5-10 micrograms/kg in 200 nl) of quinpirole into major hypothalamic nuclei of conscious, freely moving rats elicited no pressor response. Uni- or bilateral microinjections of quinpirole (5 micrograms/200 nl) into the posterior region of nucleus tractus solitarius (P-NTS) caused a consistent increase in mean arterial pressure (MAP) (Max = 12.4 +/- 1.1 mmHg, n = 12) with a rapid onset (less than 30 sec) in unanesthetized decerebrate S-D rats, while microinjections into the anterior region of NTS, area postrema, C1/A1 regions, raphe obscurus nucleus, locus coeruleus or regions 0.5 mm lateral, superior or inferior to P-NTS produced little or no response. The pressor response induced by bilateral microinjections of quinpirole into P-NTS was not different from that of unilateral microinjection. The pressor response to microinjection of quinpirole into P-NTS was abolished by pretreatment with metoclopramide (5 mg/kg, IV or 25 micrograms/200 nl, P-NTS injection; 5 min before), a selective DA D2 antagonist that crosses the blood-brain barrier.(ABSTRACT TRUNCATED AT 250 WORDS)
authors: Department of Medicine, University of Alabama, Birmingham 35294.
authors: R H
authors: RH
authors: Yang
authors: Y
authors: Y
authors: Igarashi
authors: J M
authors: JM
authors: Wyss
authors: Y F
authors: YF
authors: Chen
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000187:drug effects; D004873:Ergolines / Q000494:pharmacology*; D007276:Injections, Intraventricular; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000378:metabolism*; D019257:Quinpirole; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000378:metabolism*; D017448:Receptors, Dopamine D2
chemical_list: D004873:Ergolines; D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D019257:Quinpirole