title: Central ventilatory and cardiovascular actions of trout gastrin-releasing peptide (GRP) in the unanesthetized trout.
abstract: Gastrin-releasing peptide (GRP), a neuropeptide initially isolated from porcine stomach, shares sequence similarity with bombesin. GRP and its receptors are present in the brains and peripheral tissues of several species of teleost fish, but little is known about the ventilatory and cardiovascular effects of this peptide in these vertebrates. The goal of this study was to compare the central and peripheral actions of picomolar doses of trout GRP on ventilatory and cardiovascular variables in the unanesthetized rainbow trout. Compared to vehicle, intracerebroventricular (ICV) injection of GRP (1-50 pmol) significantly elevated the ventilation rate (ƒV) and the ventilation amplitude (VAMP), and consequently the total ventilation (VTOT). The maximum hyperventilatory effect of GRP (VTOT: +225%), observed at a dose of 50 pmol, was mostly due to its stimulatory action on VAMP (+170%) rather than ƒV (+20%). In addition, ICV GRP (50 pmol) produced a significant increase in mean dorsal aortic blood pressure (P DA) (+35%) and in heart rate (ƒH) (+25%). Intra-arterial injections of GRP (5-100 pmol) were without sustained effect on the ventilatory variables but produced sporadic and transient increases in ventilatory movement at doses of 50 and 100 pmol. At these doses, GRP elevated P DA by +20% but only the 50 pmol dose significantly increased HR (+15%). In conclusion, our study suggests that endogenous GRP within the brain of the trout may act as a potent neurotransmitter and/or neuromodulator in the regulation of cardio-ventilatory functions. In the periphery, endogenous GRP may act as locally-acting and/or circulating neurohormone with an involvement in vasoregulatory mechanisms.
authors.affiliation: Université Européenne de Bretagne, Université de Brest, INSERM UMR1101, Laboratoire de Traitement de l'Information Médicale, Laboratoire de Neurophysiologie, SFR ScInBioS, Faculté de Médecine et des Sciences de la Santé , 22 Avenue Camille Desmoulins, CS 93837, 29238 Brest Cedex 3, CHU de Brest , France.
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Le Mével
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lancien
authors.forename: Nagi
authors.initials: N
authors.lastname: Mimassi
authors.forename: Marc
authors.initials: M
authors.lastname: Kermorgant
authors.forename: J Michael
authors.initials: JM
authors.lastname: Conlon
keywords: Central GRP; Hypertension; Hyperventilation; Intracerebroventricular injection; Teleost