Ventilatory and cardiovascular actions of centrally administered trout tachykinins in the unanesthetized trout.
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 (NPgamma), 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 NPgamma 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 NPgamma was to produce an hypoventilatory response since the total ventilation (V(TOT)) was significantly reduced. The minimum effective dose for a significant effect of NPgamma 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 NPgamma, produce a strong hypoventilatory response in a teleost fish and so suggest that endogenous tachykinins may be differentially implicated in neuroregulatory control of ventilation.
Le Mével
Jean-Claude
JC
Laboratoire de Traitement de l'Information Médicale, INSERM U650, Faculté de Médecine et des Sciences de la Santé, Université de Bretagne Occidentale, 22 avenue Camille Desmoulins, CS 93837, 29238 Brest Cedex 3, France. jean-claude.lemevel@univ-brest.fr
Lancien
Frédéric
F
Mimassi
Nagi
N
Conlon
J Michael
JM
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004333:Drug Administration Routes; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D015288:Neurokinin A / Q000008:administration & dosage / Q000494:pharmacology; D017686:Oncorhynchus mykiss / Q000502:physiology*; D010101:Oxygen Consumption / Q000187:drug effects*; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology; D013373:Substance P / Q000008:administration & dosage / Q000494:pharmacology; D015320:Tachykinins / Q000008:administration & dosage / Q000494:pharmacology*
D010446:Peptide Fragments; D015320:Tachykinins; C059905:tachykinin neuropeptide gamma; D013373:Substance P; D015288:Neurokinin A