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First published online August 31, 2007
Journal of Experimental Biology 210, 3301-3310 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.006106

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Ventilatory and cardiovascular actions of centrally administered trout tachykinins in the unanesthetized trout

Jean-Claude Le Mével^1,*, Frédéric Lancien¹, Nagi Mimassi¹ and J. Michael Conlon²

¹ Laboratoire de Traitement de l'Information Médicale, INSERM U650, and Laboratoire de Neurophysiologie, Faculté de Médecine et des Sciences de la Santé, Université de Bretagne Occidentale, 22 avenue Camille Desmoulins, CS 93837, 29238 Brest Cedex 3, France
² Department of Biochemistry, Faculty of Medicine and Health Sciences, United Arab Emirates University, 17666 Al Ain, United Arab Emirates

^* Author for correspondence (e-mail: jean-claude.lemevel{at}univ-brest.fr)

Accepted 17 July 2007

The brains of teleost fish contain members of the tachykinin family that are the products of orthologous genes expressed in mammalian nervous tissues, but little is known regarding the physiological effects of these peptides in their species of origin. The present study compares the central actions of trout neuropeptide gamma (NP), substance P (SP) and neurokinin A (NKA) (5–250 pmol) on ventilatory and cardiovascular parameters in the unanesthetized rainbow trout Oncorhynchus mykiss. Intracerebroventricular (ICV) injection of NP evoked a dose-dependent elevation of the ventilation rate (f_V) but a reduction of the ventilation amplitude (V_AMP) that was caused by a reduction of the magnitude of the adduction phase of the ventilatory signal. The net effect of NP was to produce an hypoventilatory response since the total ventilation (V_TOT) was significantly reduced. The minimum effective dose for a significant effect of NP on f_V and V_AMP was 50 pmol. SP evoked a significant elevation of f_V, a concomitant depression of V_AMP, and a resultant decrease in V_TOT but only at the highest dose (250 pmol). NKA was without action on f_V but significantly decreased V_AMP at only the highest dose tested. In this case also, the net effect of NKA was to reduce V_TOT. When injected centrally, none of the three peptides, at any dose tested, produced changes in heart rate or mean dorsal aortic blood pressure (P_DA). Intra-arterial injection of the three tachykinins (250 pmol) produced a significant (P<0.05) increase in P_DA, but only SP and NKA induced concomitant bradycardia. None of the three peptides produced any change in f_V or V_AMP. In conclusion, our results demonstrate that centrally injected tachykinins, particularly NP, produce a strong hypoventilatory response in a teleost fish and so suggest that endogenous tachykinins may be differentially implicated in neuroregulatory control of ventilation.

Key words: neuropeptide , substance P, neurokinin A, ventilatory control, intracerebroventricular injection, teleost

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