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

Abstract

SUMMARY 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 (NPγ), 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 NPγ evoked a dose-dependent elevation of the ventilation rate (fV) but a reduction of the ventilation amplitude (VAMP) that was caused by a reduction of the magnitude of the adduction phase of the ventilatory signal. The net effect of NPγ was to produce an hypoventilatory response since the total ventilation (VTOT) was significantly reduced. The minimum effective dose for a significant effect of NPγ on fV and VAMP was 50 pmol. SP evoked a significant elevation of fV, a concomitant depression of VAMP, and a resultant decrease in VTOTbut only at the highest dose (250 pmol). NKA was without action on fV but significantly decreased VAMP at only the highest dose tested. In this case also, the net effect of NKA was to reduce VTOT. When injected centrally, none of the three peptides, at any dose tested, produced changes in heart rate or mean dorsal aortic blood pressure (PDA). Intra-arterial injection of the three tachykinins (250 pmol) produced a significant (P<0.05)increase in PDA, but only SP and NKA induced concomitant bradycardia. None of the three peptides produced any change in fV or VAMP. In conclusion, our results demonstrate that centrally injected tachykinins, particularly NPγ,produce a strong hypoventilatory response in a teleost fish and so suggest that endogenous tachykinins may be differentially implicated in neuroregulatory control of ventilation.

Cod CGRP and tachykinins in coeliac artery innervation of the Atlantic cod, Gadus morhua: presence and vasoactivity

“…In vivo studies on rainbow trout showed that bolus (intra-arterial) injections of trout SP initially increased coeliac artery blood flow but subsequently, about 3 min after the injection of the peptide, the resistance increased, causing a reduction in flow (Kågström et al 1996). This unusual reduction in flow was corroborated in similar studies in the rainbow trout, using trout SP and the even more potent trout NKA (Le Mével et al 2007). In contrast, in vitro, trout SP and NKA only increased vascular resistance in 45% of the exposures in the rainbow trout (Kågström and Holmgren 1998).…”

Central ventilatory and cardiovascular actions of trout gastrin-releasing peptide (GRP) in the unanesthetized trout

“…Because the hypothalamic region in the rainbow trout brain contains the largest number of SP-immunoreactive and GRP neurons and fibers (Vecino et al, 1989; Cuadrado et al, 1994), possible interaction among both neuropeptides may be of physiological importance to permit the fine control of cardiovascular and ventilatory functions. The consequence of this possible interaction is unknown, but we have previously shown that ICV injection of SP in trout decreases V TOT (Le Mével et al, 2007). Further studies are clearly required to elucidate the precise location of GRP-producing elements, the distribution of GRPR, and to reveal which pathways are recruited and under which circumstances the GRP and other neuropeptidergic systems are triggered to participate in integrative and homeostatic cardio-ventilatory regulations.…”

“…The time-series related to the ventilatory, the pulsatile P DA and the ECG signals were then processed off-line with custom-made programs written in LabView 6.1 (Laboratory Virtual Instrument Engineering Workbench, National Instruments, Austin, USA). The ventilatory and cardiovascular variables were calculated as previously described (Lancien et al, 2004; Le Mével et al, 2007). Segments free of any movement artifacts on the ventilatory signal were selected and ƒV (breaths min −1 ) and V AMP (arbitrary units, a.u.)…”

Brain neuropeptides in central ventilatory and cardiovascular regulation in trout

“…Neuroanatomical studies have revealed the presence of tachykinin-like immunoreactivity in neuronal cell bodies and fibers throughout the brains of several teleost fish, including the trout (Vecino et al, 1989; Batten et al, 1990; Holmqvist and Ekstrom, 1991; Moons et al, 1992) together with high density of tachykinin binding sites from the hypothalamus to the medulla oblongata (Moons et al, 1992). We recently demonstrated that, after ICV injection, exogenously administered trout tachykinins are differentially implicated in the neuroregulatory control of ventilation in trout (Le Mével et al, 2007). …”