1
|
Costa KM, Accorsi-Mendonça D, Moraes DJA, Machado BH. Evolution and physiology of neural oxygen sensing. Front Physiol 2014; 5:302. [PMID: 25161625 PMCID: PMC4129633 DOI: 10.3389/fphys.2014.00302] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 07/23/2014] [Indexed: 01/06/2023] Open
Abstract
Major evolutionary trends in animal physiology have been heavily influenced by atmospheric O2 levels. Amongst other important factors, the increase in atmospheric O2 which occurred in the Pre-Cambrian and the development of aerobic respiration beckoned the evolution of animal organ systems that were dedicated to the absorption and transportation of O2, e.g., the respiratory and cardiovascular systems of vertebrates. Global variations of O2 levels in post-Cambrian periods have also been correlated with evolutionary changes in animal physiology, especially cardiorespiratory function. Oxygen transportation systems are, in our view, ultimately controlled by the brain related mechanisms, which senses changes in O2 availability and regulates autonomic and respiratory responses that ensure the survival of the organism in the face of hypoxic challenges. In vertebrates, the major sensorial system for oxygen sensing and responding to hypoxia is the peripheral chemoreflex neuronal pathways, which includes the oxygen chemosensitive glomus cells and several brainstem regions involved in the autonomic regulation of the cardiovascular system and respiratory control. In this review we discuss the concept that regulating O2 homeostasis was one of the primordial roles of the nervous system. We also review the physiology of the peripheral chemoreflex, focusing on the integrative repercussions of chemoreflex activation and the evolutionary importance of this system, which is essential for the survival of complex organisms such as vertebrates. The contribution of hypoxia and peripheral chemoreflex for the development of diseases associated to the cardiovascular and respiratory systems is also discussed in an evolutionary context.
Collapse
Affiliation(s)
| | | | | | - Benedito H. Machado
- Laboratory of Autonomic and Respiratory Control, Department of Physiology, School of Medicine of Ribeirão Preto, University of São PauloRibeirão Preto, Brazil
| |
Collapse
|
2
|
Porteus CS, Abdallah SJ, Pollack J, Kumai Y, Kwong RWM, Yew HM, Milsom WK, Perry SF. The role of hydrogen sulphide in the control of breathing in hypoxic zebrafish (Danio rerio). J Physiol 2014; 592:3075-88. [PMID: 24756639 DOI: 10.1113/jphysiol.2014.271098] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The current study investigated the role of hydrogen sulphide (H2S) in oxygen sensing, intracellular signalling and promotion of ventilatory responses to hypoxia in adult and larval zebrafish (Danio rerio). Both larval and adult zebrafish exhibited a dose-dependent increase in ventilation to sodium sulphide (Na2S), an H2S donor. In vertebrates, cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) are enzymes that catalyse the endogenous production of H2S. In adult zebrafish, inhibition of both CBS and CSE with aminooxyacetate (AOA) and propargyl glycine (PPG) blunted or abolished the hypoxic hyperventilation, and the addition of Na2S to the water partially rescued the effects of inhibiting endogenous H2S production. In zebrafish larvae (4 days post-fertilization), gene knockdown of either CBS or CSE using morpholinos attenuated the hypoxic ventilatory response. Furthermore, the intracellular calcium concentration of isolated neuroepithelial cells (NECs), which are putative oxygen chemoreceptors, increased significantly when these cells were exposed to 50 μm Na2S, supporting a role for H2S in Ca(2+)-evoked neurotransmitter release in these cells. Finally, immunohistochemical labelling showed that NECs dissociated from adult gill contained CBS and CSE, whereas cutaneous NECs in larval zebrafish expressed only CSE. Taken together, these data show that H2S can be produced in the putative oxygen-sensing cells of zebrafish, the NECs, in which it appears to play a pivotal role in promoting the hypoxic ventilatory response.
Collapse
Affiliation(s)
- Cosima S Porteus
- Department of Biosciences, University of British Columbia, Vancouver, BC, Canada
| | - Sara J Abdallah
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Jacob Pollack
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Yusuke Kumai
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | | | - Hong M Yew
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - William K Milsom
- Department of Biosciences, University of British Columbia, Vancouver, BC, Canada
| | - Steve F Perry
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| |
Collapse
|
3
|
Brainstem mechanisms controlling cardiovascular reflexes in channel catfish. Comp Biochem Physiol A Mol Integr Physiol 2014; 170:1-5. [PMID: 24434806 DOI: 10.1016/j.cbpa.2014.01.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 12/24/2013] [Accepted: 01/06/2014] [Indexed: 12/29/2022]
Abstract
Microinjections of kynurenic acid and kainic acid into the general visceral nucleus (nGV), homologous to the mammalian nucleus tractus solitarius of the medulla, in anesthestized, spontaneously breathing catfish were used to identify central areas and mechanisms controlling resting normoxic heart rate and blood pressure and the cardiovascular responses to hypoxia. Kynurenic acid, an antagonist of ionotropic glutamate receptors, significantly reduced resting normoxic heart rate but did not block the bradycardia associated with aquatic hypoxia. Kainic acid (an excitotoxic glutamatergic receptor agonist) also significantly reduced normoxic heart rate, but blocked the hypoxia-induced bradycardia. Neither kynurenic acid nor kainic acid microinjections affected blood pressure in normoxia or hypoxia. The results of this study indicate that glutamatergic receptors in the nGV are involved in the maintenance of resting heart rate and the destruction of these neurons with kainic acid abolishes the bradycardia associated with aquatic hypoxia.
Collapse
Key Words
- Chemosensitivity, Central
- Receptors, NMDA, AMPA
- heart rate, blood pressure, general visceral nucleus, fish, hypoxia, kainic acid, kynurenic acid, kainic acid
Collapse
|
4
|
Le Mével JC, Lancien F, Mimassi N, Conlon JM. Brain neuropeptides in central ventilatory and cardiovascular regulation in trout. Front Endocrinol (Lausanne) 2012; 3:124. [PMID: 23115556 PMCID: PMC3483629 DOI: 10.3389/fendo.2012.00124] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Accepted: 10/01/2012] [Indexed: 12/20/2022] Open
Abstract
Many neuropeptides and their G-protein coupled receptors (GPCRs) are present within the brain area involved in ventilatory and cardiovascular regulation but only a few mammalian studies have focused on the integrative physiological actions of neuropeptides on these vital cardio-respiratory regulations. Because both the central neuroanatomical substrates that govern motor ventilatory and cardiovascular output and the primary sequence of regulatory peptides and their receptors have been mostly conserved through evolution, we have developed a trout model to study the central action of native neuropeptides on cardio-ventilatory regulation. In the present review, we summarize the most recent results obtained using this non-mammalian model with a focus on PACAP, VIP, tachykinins, CRF, urotensin-1, CGRP, angiotensin-related peptides, urotensin-II, NPY, and PYY. We propose hypotheses regarding the physiological relevance of the results obtained.
Collapse
Affiliation(s)
- Jean-Claude Le Mével
- INSERM UMR 1101, Laboratoire de Traitement de l'Information Médicale, Laboratoire de Neurophysiologie, SFR ScInBioS, Faculté de Médecine et des Sciences de la Santé, Université Européenne de Bretagne, Université de Brest, CHU de BrestBrest, France
- *Correspondence: Jean-Claude Le Mével, INSERM UMR 1101, Laboratoire de Traitement de l'Information Médicale, Laboratoire de Neurophysiologie, SFR ScInBioS, Faculté de Médecine et des Sciences de la Santé, Université Européenne de Bretagne, Université de Brest, CHU de Brest, 22 avenue Camille Desmoulins, CS 93837, 29238 Brest Cedex 3, France. e-mail:
| | - Frédéric Lancien
- INSERM UMR 1101, Laboratoire de Traitement de l'Information Médicale, Laboratoire de Neurophysiologie, SFR ScInBioS, Faculté de Médecine et des Sciences de la Santé, Université Européenne de Bretagne, Université de Brest, CHU de BrestBrest, France
| | - Nagi Mimassi
- INSERM UMR 1101, Laboratoire de Traitement de l'Information Médicale, Laboratoire de Neurophysiologie, SFR ScInBioS, Faculté de Médecine et des Sciences de la Santé, Université Européenne de Bretagne, Université de Brest, CHU de BrestBrest, France
| | - J. Michael Conlon
- Department of Biochemistry, Faculty of Medicine and Health Sciences, United Arab Emirates UniversityAl Ain, United Arab Emirates
| |
Collapse
|
5
|
Turesson J, Johansson M, Sundin L. Involvement of non-NMDA receptors in central mediation of chemoreflexes in the shorthorn sculpin, Myoxocephalus scorpius. Respir Physiol Neurobiol 2010; 172:83-93. [DOI: 10.1016/j.resp.2010.03.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Revised: 02/25/2010] [Accepted: 03/19/2010] [Indexed: 10/19/2022]
|
6
|
Le Mével JC, Lancien F, Mimassi N, Conlon JM. Ventilatory and cardiovascular actions of centrally and peripherally administered trout pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) in the unanaesthetized trout. J Exp Biol 2009; 212:3919-27. [DOI: 10.1242/jeb.035196] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
SUMMARY
In mammals, pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are involved in cardiovascular and respiratory regulation. Several studies have demonstrated the presence of PACAP, VIP and their receptors in various tissues of teleost fish, including the brain, but little is known about their respiratory and cardiovascular effects. The present study was undertaken to compare the central and peripheral actions of graded doses (25-100 pmol) of trout PACAP and trout VIP on ventilatory and cardiovascular variables in the unanaesthetized rainbow trout. Compared with vehicle, only intracerebroventricular injection of PACAP significantly (P<0.05) elevated the ventilation frequency and the ventilation amplitude, but both peptides significantly increased the total ventilation (). However, the maximum hyperventilatory effect of PACAP was approximately 2.5-fold higher than the effect of VIP at the 100 pmol dose (PACAP, =+5407±921 arbitrary units, a.u.; VIP, =+2056±874 a.u.; means ± s.e.m.). When injected centrally, only PACAP produced a significant increase in mean dorsal aortic blood pressure (PDA) (100 pmol: +21%) but neither peptide affected heart rate (fH). Intra-arterial injections of either PACAP or VIP were without effect on the ventilatory variables. PACAP was without significant action on PDA and fH while VIP significantly elevated PDA (100 pmol: +36%) without changing fH. In conclusion, the selective central hyperventilatory actions of exogenously administered trout PACAP, and to a lesser extent VIP, suggest that the endogenous peptides may be implicated in important neuroregulatory functions related to the central control of ventilation in trout.
Collapse
Affiliation(s)
- J.-C. Le Mével
- Université Européenne de Bretagne, Université de Brest, INSERM U650, Laboratoire de Traitement de l'Information Médicale, Laboratoire de Neurophysiologie, IFR 148 ScInBioS, Faculté de Médecine et des Sciences de la Santé, 22 Avenue Camille Desmoulins, CS 93837, 29238 Brest Cedex 3, CHU de Brest, France
| | - F. Lancien
- Université Européenne de Bretagne, Université de Brest, INSERM U650, Laboratoire de Traitement de l'Information Médicale, Laboratoire de Neurophysiologie, IFR 148 ScInBioS, Faculté de Médecine et des Sciences de la Santé, 22 Avenue Camille Desmoulins, CS 93837, 29238 Brest Cedex 3, CHU de Brest, France
| | - N. Mimassi
- Université Européenne de Bretagne, Université de Brest, INSERM U650, Laboratoire de Traitement de l'Information Médicale, Laboratoire de Neurophysiologie, IFR 148 ScInBioS, Faculté de Médecine et des Sciences de la Santé, 22 Avenue Camille Desmoulins, CS 93837, 29238 Brest Cedex 3, CHU de Brest, France
| | - J. M. Conlon
- Department of Biochemistry, Faculty of Medicine and Health Sciences, United Arab Emirates University, 17666 Al Ain, United Arab Emirates
| |
Collapse
|
7
|
Le Mével JC, Lancien F, Mimassi N, Conlon JM. Central hyperventilatory action of the stress-related neurohormonal peptides, corticotropin-releasing factor and urotensin-I in the trout Oncorhynchus mykiss. Gen Comp Endocrinol 2009; 164:51-60. [PMID: 19341734 DOI: 10.1016/j.ygcen.2009.03.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Revised: 03/03/2009] [Accepted: 03/23/2009] [Indexed: 01/23/2023]
Abstract
The stress-related neurohormonal peptides corticotropin-releasing factor (CRF) and urotensin-I (U-I), an ortholog of mammalian urocortin 1, are widely distributed in the central nervous systems of teleost fish but little is known about their possible central neurotropic actions. In the present study, we investigated the effect of intracerebroventricular (ICV) injection of CRF and U-I (1-10pmol) on ventilatory and cardiovascular variables in our established unanaesthetized trout model. CRF and U-I produced a significant dose-dependent and long-lasting increase in the ventilatory frequency (VF) and the ventilatory amplitude (VA). Consequently the net effect of these peptides was a hyperventilatory response since the total ventilation (VTOT) was significantly elevated. However, CRF evoked a significant hyperventilatory response 5-10min sooner than that observed after ICV administration of U-I and the hyperventilatory effect of 10pmol CRF was twofold higher than that of equimolar dose of U-I. Pre-treatment of the trout with the antagonist, alpha-helical CRF(9-41), significantly reduced by about threefold the CRF-induced increase in VF, VA and VTOT. The most significant cardiovascular action of central CRF and U-I was to evoke a hypertensive response without changing the heart rate. Peripheral injection of CRF and U-I at doses of 5 and 50pmol produced no change in VF, VA or VTOT. Only a transient hypertensive response without change in heart rate was observed after the injection of the highest dose of U-I. Our results demonstrate that in a teleost fish, CRF and U-I produce a potent hyperventilatory response only when injected centrally. The two endogenous stress-related neuropeptides may play an important stimulatory role acting as neurotransmitters and/or neuromodulators in the central control of ventilatory apparatus during stress.
Collapse
Affiliation(s)
- Jean-Claude Le Mével
- Université Européenne de Bretagne, Université de Brest, INSERM U650, Laboratoire de Traitement de l'Information Médicale, IFR 148 ScInBioS, Faculté de Médecine et des Sciences de la Santé, Brest, CHU de Brest, France.
| | | | | | | |
Collapse
|
8
|
Burleson ML. Sensory innervation of the Gills: O2-sensitive chemoreceptors and mechanoreceptors. Acta Histochem 2009; 111:196-206. [PMID: 19193399 DOI: 10.1016/j.acthis.2008.11.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Physical characteristics of water (O(2) solubility and capacitance) dictate that cardiovascular and ventilatory performance be controlled primarily by the need for oxygen uptake rather than carbon dioxide excretion, making O(2) receptors more important in fish than in terrestrial vertebrates. An understanding of the anatomy and physiology of mechanoreception and O(2) chemoreception in fishes is important, because water breathing is the primitive template upon which the forces of evolution have modified into the various cardioventilatory modalities we see in extant terrestrial species. Key to these changes are the O(2)-sensitive chemoreceptors and mechanoreceptors, their mechanisms and central pathways.
Collapse
|
9
|
Perry S, Jonz M, Gilmour K. Chapter 5 Oxygen Sensing And The Hypoxic Ventilatory Response. FISH PHYSIOLOGY 2009. [DOI: 10.1016/s1546-5098(08)00005-8] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
10
|
Le Mével JC, Lancien F, Mimassi N, Conlon JM. Ventilatory and cardiovascular actions of centrally administered trout tachykinins in the unanesthetized trout. J Exp Biol 2007; 210:3301-10. [PMID: 17766308 DOI: 10.1242/jeb.006106] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYThe 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.
Collapse
Affiliation(s)
- Jean-Claude Le Mével
- 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.
| | | | | | | |
Collapse
|
11
|
Turesson J, Schwerte T, Sundin L. Late onset of NMDA receptor-mediated ventilatory control during early development in zebrafish (Danio rerio). Comp Biochem Physiol A Mol Integr Physiol 2006; 143:332-9. [PMID: 16458555 DOI: 10.1016/j.cbpa.2005.12.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2005] [Revised: 12/05/2005] [Accepted: 12/05/2005] [Indexed: 11/24/2022]
Abstract
Increased ventilation frequency (fV) in response to hypoxia in adult fish depends on ionotropic N-methyl-D-aspartate (NMDA) receptors. Nonetheless, the ontogeny of central control mechanisms mediating hypoxic ventilatory chemoreflexes in lower vertebrates has not been studied. Therefore, the aim of this study was to determine when the hypoxic ventilatory response during zebrafish (Danio rerio) development is mediated via NMDA receptors, by performing physiological experiments and western blot analysis of NMDA receptor subunits. Zebrafish larvae at stages 4-16 days post-fertilisation (dpf) were exposed to an hypoxic pulse in control groups and in groups treated with MK801 (NMDA receptor antagonist). The hypoxic increase in fV was present at all larval stages, and it matured during development. The reflex became MK801 sensitive at 8 dpf, but did not completely rely on a glutamatergic transmission until 13 dpf. This, together with changing subunit composition during the different stages (increasing amounts of NMDAR1 subunits and appearance of NMDAR2A subunits in adults), suggests that the amount of functional NMDA receptors needed to achieve a fully developed reflex is not attained until later stages. Furthermore, our results suggest that other non-NMDA receptor mechanisms are responsible for the hypoxia-induced increase in fV during the earlier developmental stages.
Collapse
Affiliation(s)
- J Turesson
- Department of Zoophysiology, Göteborg University, Box 463, S-405 30, Göteborg, Sweden.
| | | | | |
Collapse
|
12
|
Gilmour KM, Perry SF. Branchial Chemoreceptor Regulation of Cardiorespiratory Function. FISH PHYSIOLOGY 2006. [DOI: 10.1016/s1546-5098(06)25003-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
|
13
|
Bernier NJ, Craig PM. CRF-related peptides contribute to stress response and regulation of appetite in hypoxic rainbow trout. Am J Physiol Regul Integr Comp Physiol 2005; 289:R982-90. [PMID: 15932968 DOI: 10.1152/ajpregu.00668.2004] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hypoxia stress suppresses appetite in a variety of fish species, but the mechanisms mediating this response are not known. Therefore, given their anorexigenic and hypophysiotropic properties, we investigated the contribution of forebrain corticotropin-releasing factor (CRF) and urotensin I (UI) to the regulation of food intake and the hypothalamic-pituitary-interrenal (HPI) stress axis in hypoxic rainbow trout. Exposure to 50 and 35% O(2) saturation for 24 h decreased food intake by 28 and 48%, respectively. The 35% O(2) treatment also increased forebrain CRF and UI mRNA levels, plasma cortisol, and lactate. Exposure for 72 h to the same conditions resulted in similar reductions in food intake, increases in plasma cortisol proportional to the hypoxia severity, and increases in forebrain CRF and UI mRNA levels in the 50% O(2) treatment. Relative to saline-infused fish, chronic intracranial infusion of the CRF receptor antagonist alpha-helical CRF((9-41)) reduced the appetite-suppressing effects of 24-h exposure to 35% O(2) and blocked the hypoxia-induced increase in plasma cortisol. Finally, forebrain microdissection revealed that 50 and 35% O(2) exposure for 24 h specifically increases preoptic area CRF and UI mRNA levels in proportion to the severity of the hypoxic challenge and either has no effect or elicits small decreases in other forebrain regions. These results show that CRF-related peptides play a physiological role in regulating the HPI axis and in mediating at least a portion of the reduction in food intake under hypoxic conditions in rainbow trout and demonstrate that the response of forebrain CRF and UI neurons to this stressor is region specific.
Collapse
Affiliation(s)
- Nicholas J Bernier
- Department of Integrative Biology, University of Guelph, 50 Stone Road East, Guelph, ON, Canada N1G 2W1.
| | | |
Collapse
|