title: Cardiovascular responses to microinjections of nociceptin into a midline area in the commissural subnucleus of the nucleus tractus solitarius of the rat.
abstract: Immunoreactivity for nociceptin, an endogenous ligand for the ORL1 opioid receptors, has been reported in the nucleus tractus solitarius (nTS). A midline area in the commissural subnucleus (nCom) of nTS is the site of peripheral chemoreceptor projections. This investigation was carried out in urethane-anesthetized, artificially ventilated, adult male Wistar rats, to study the cardiovascular effects of the activation of ORL1 receptors in a midline area of the nCom. Microinjections (30 nl) of nociceptin (0.15-0.62 mM) into the nCom elicited depressor and bradycardic responses. Prior microinjections of [N-Phe(1)]-nociceptin-(1-13)-NH(2) (4.5 mM), a specific antagonist for ORL1 opioid receptors, into the nCom blocked the effects of nociceptin (0.31 mM, the maximally effective concentration), but not endomorphin-2 (0.6 mM; an endogenous ligand for micro -opioid receptors). On of other hand, naloxone (0.125 mM; an antagonist for classical opioid receptors) did not block the effects of nociceptin, while it did block the effects of endomorphin-2. The blockade of nociceptin effects by [N-Phe(1)]-nociceptin-(1-13)-NH(2) and endomorphin-2 by naloxone, was not due to some nonspecific effects because the responses to L-Glu (5 mM) remained unaltered after the microinjection of these antagonists. These results indicate that activation of ORL1 receptors in the nCom may play a role in the regulation of cardiovascular function.
authors.affiliation: Department of Neurological Surgery, MSB H-586, New Jersey Medical School, 185 South Orange Ave., Newark, NJ 07103, USA.
authors.forename: Neel
authors.initials: N
authors.lastname: Shah
authors.forename: Vineet C
authors.initials: VC
authors.lastname: Chitravanshi
authors.forename: Hreday N
authors.initials: HN
authors.lastname: Sapru
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002319:Cardiovascular System / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D008297:Male; D008845:Microinjections / Q000379:methods*; D009292:Narcotic Antagonists / Q000494:pharmacology; D018847:Opioid Peptides / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011957:Receptors, Opioid / Q000819:agonists / Q000502:physiology; D017552:Solitary Nucleus / Q000187:drug effects* / Q000502:physiology; D000094942:Nociceptin Receptor; D000097629:Nociceptin
chemical_list: D009292:Narcotic Antagonists; D018847:Opioid Peptides; D011957:Receptors, Opioid; D000094942:Nociceptin Receptor; D000097629:Nociceptin; C000722285:Oprl1 protein, rat