Corticotropin releasing factor induces anxiogenic locomotion in trout and alters serotonergic and dopaminergic activity

Corticotropin releasing factor (CRF) and serotonin (5-HT) are strongly linked to stress and anxiety in vertebrates. As a neuromodulator in the brain, CRF has anxiogenic properties often characterized by increased locomotion and stereotyped behavior in familiar environments. We hypothesized that expression of anxiogenic behavior in response to CRF will also be exhibited in a teleost fish. Rainbow trout were treated with intracerebroventricular (icv) injections of artificial cerebrospinal fluid (aCSF), 500 or 2000 ng ovine CRF, or not injected. Treatment with either dose of CRF elicited greater locomotion and pronounced head shaking behavior but did not influence water column position. Locomotor and head shaking behaviors may be analogous to the increased stereotypy evoked by icv CRF in rats and may reflect the expression of stress/anxiety behavior. Injection with either aCSF or CRF produced significant increases in plasma cortisol. The absence of behavioral changes in aCSF-injected fish suggests that the behavioral responses following CRF were not due to cortisol. Treatment with 2000 ng CRF significantly increased serotonin, 5-HIAA and dopamine concentrations in the subpallium and raphé and increased 5-HIAA in the preoptic hypothalamus (POA). Concurrent effects of CRF on central monoamines, locomotion and head shaking in trout suggest that anxiogenic properties of CRF are evolutionarily conserved. In addition, positive linear correlations between locomotion and serotonergic and dopaminergic function in the subpallium, POA and raphé nuclei suggest a locomotory function for these monoamines.     

Food-deprivation induces HSP70 and HSP90 protein expression in larval gilthead sea bream and rainbow trout

Heat shock proteins (HSPs) expression is commonly used as indicators of cellular stress in animals. However, very little is known about either the expression patterns of HSPs or their role in the stress-tolerance phenomenon in early life stages of fish. To this end, we examined the impact of food-deprivation (12 h), reduced oxygen levels (3.5 mg/L for 1 h) and heat shock (HS: + 5 °C for 1 h) on HSP70 and HSP90 protein expression in early life stages of the gilthead sea bream (Sparus aurata), a warm-water aquaculture species. Also, we investigated HSP70 and HSP90 response to food-deprivation (7 days) in early life stages of rainbow trout (Oncorhynchus mykiss), a cool-water aquaculture species, and the tolerance of this larvae to heat shock (either + 5 or + 10 °C for 1 h). Our results clearly demonstrate that food-deprivation enhances HSP70 and HSP90 protein expression in larvae of both species. In gilthead sea bream larvae, the stressors-induced HSP70 and HSP90 (only in the reduced oxygen group) protein expression returned to unstressed levels after 24 h recovery. In fed trout larvae, a + 5 °C heat shock did not elevate HSP70 and HSP90 expression, whereas 100% mortality was evident with a + 10 °C HS. However, food-deprived trout larvae, which had higher HSP70 and HSP90 protein content, survived HS and showed HS-dependent increases in HSP70, but not HSP90 expression. Overall, HSP70 and HSP90 protein expression in early life stages of fish have the potential to be used as markers of nutritional stress, while elevation of the tissue HSPs content may be used as a means to increase stress tolerance during larval rearing.     

A cDNA microarray assessment of gene expression in the liver of rainbow trout (Oncorhynchus mykiss) in response to a handling and confinement stressor

A purpose-designed microarray platform (Stressgenes, Phase 1) was utilised to investigate the changes in gene expression within the liver of rainbow trout during exposure to a prolonged period of confinement. Tissue and blood samples were collected from trout at intervals up to 648 h after transfer to a standardised confinement stressor, together with matched samples from undisturbed control fish. Plasma ACTH, cortisol, glucose and lactate were analysed to confirm that the neuroendocrine response to confinement was consistent with previous findings and to provide a phenotypic context to assist interpretation of gene expression data. Liver samples for suppression subtractive hybridisation (SSH) library construction were selected from within the experimental groups comprising “early” stress (2–48 h) and “late” stress (96–504 h). In order to reduce redundancy within the four SSH libraries and yield a higher number of unique clones an additional subtraction was carried out. After printing of the arrays a series of 55 hybridisations were executed to cover 6 time points. At 2 h, 6 h, 24 h, 168 h and 504 h 5 individual confined fish and 5 individual control fish were used with control fish only at 0 h. A preliminary list of 314 clones considered differentially regulated over the complete time course was generated by a combination of data analysis approaches and the most significant gene expression changes were found to occur during the 24 h to 168 h time period with a general approach to control levels by 504 h. Few changes in expression were apparent over the first 6 h. The list of genes whose expression was significantly altered comprised predominantly genes belonging to the biological process category (response to stimulus) and one cellular component category (extracellular region) and were dominated by so-called acute phase proteins. Analysis of the gene expression profile in liver tissue during confinement revealed a number of significant clusters. The major patterns comprised genes that were up-regulated at 24 h and beyond, the primary examples being haptoglobin, β-fibrinogen and EST10729. Two representative genes from each of the six k-means clusters were validated by qPCR. Correlations between microarray and qPCR expression patterns were significant for most of the genes tested. qPCR analysis revealed that haptoglobin expression was up-regulated approximately 8-fold at 24 h and over 13-fold by 168 h.     

Parvalbumin expression in trout swimming muscle correlates with relaxation rate

Rainbow trout (Oncorhynchus mykiss) display longitudinal and developmental shifts in muscle relaxation rate. This study aimed to determine the role of variations in parvalbumin content in modulating muscle relaxation. Parvalbumin is a low molecular weight protein that buffers myoplasmic Ca2+ and enhances muscle relaxation. In some fish, longitudinal variations in muscle relaxation have been linked to variations in the total amount of parvalbumin present in muscle and in the relative expression of two parvalbumin isoforms. We have demonstrated previously that anterior slow-twitch or red myotomal muscle relaxes more rapidly than that from the posterior for both rainbow and brook trout. Further, younger rainbow trout parr have faster red muscle relaxation rates than older smolts. Here we report similar results for fast-twitch or white muscle. We quantified the parvalbumin expression in red and white muscle from different body positions of rainbow trout parr and smolts and for brook trout (Salvelinus fontinalis) adults. There was a significant shift in total parvalbumin content of muscle: the faster muscle from the anterior myotome contained greater amounts of parvalbumin. For brook trout, longitudinal variation in relaxation rate was also associated with shifts in the relative expression of the two parvalbumin isoforms. The faster muscle of parr contained more parvalbumin. Lastly, trout white muscle tended to have higher levels of parvalbumin and greater levels of the Parv2 (relative to Parv1) isoform as compared to red muscle. Parvalbumin expression correlated with muscle relaxation rate in trout, although there were species-specific differences in the importance of altering total parvalbumin content versus shifts in relative parvalbumin isoform expression.     

Effect of starvation and refeeding on digestive enzyme activities in sturgeon (Acipenser naccarii) and trout (Oncorhynchus mykiss)

The digestive enzyme activities were determined in Adriatic sturgeon and rainbow trout during starvation and refeeding period. Overall, the digestive enzyme activities are affected in the same sense in both species. The protease and lipase activities were decreased later than amylase activity. Even after 1 month of starvation, both species would be prepared to digest protein and lipids in an effective way. After 72 days of starvation, the digestive machinery of the sturgeon and of the trout shows an altered capacity to digest macronutrients. The capacity to digest proteins and lipids, after 60 days of refeeding, begins to become re-established in sturgeon and trout. In contrast, in this period, the capacity to digest carbohydrates remains depressed in both species.     

Innate immune responses in rainbow trout (Oncorhynchus mykiss, Walbaum) induced by probiotics

Carnobacterium maltaromaticum B26 and Carnobacterium divergens B33, which were isolated from the intestine of healthy rainbow trout (Oncorhynchus mykiss, Walbaum), were selected as being potentially useful as probiotics with effectiveness against Aeromonas salmonicida and Yersinia ruckeri. Thus, rainbow trout administered with feed supplemented with B26 or B33 dosed at >10(7) cells g(-1) feed conferred protection against challenge with virulent cultures of the pathogens. Moreover, both cultures persisted in the gut for up to 3 weeks after administration. The cultures enhanced the cellular and humoral immune responses. Specifically, fish fed with B26 demonstrated significantly increased phagocytic activity of the head kidney macrophages, whereas the use of B33 led to significant increases in respiratory burst and serum lysozyme activity. Also, the gut mucosal lysozyme activity for fish fed with both cultures was statistically higher than the controls.     

Variability of kokanee and rainbow trout food habits,distribution, and population dynamics,in an ultraoligotrophic lake with no manipulative management

Crater Lake is a unique environment to evaluate the ecology of introduced kokanee and rainbow trout because of its otherwise pristine state, low productivity, absence of manipulative management, and lack of lotic systems for fish spawning. Between 1986 and 2004, kokanee displayed a great deal of variation in population demographics with a pattern that reoccurred in about 10 years. We believe that the reoccurring pattern resulted from density dependent growth, and associated changes in reproduction and abundance, driven by prey resource limitation that resulted from low lake productivity exacerbated by prey consumption when kokanee were abundant. Kokanee fed primarily on small-bodied prey from the mid-water column; whereas rainbow trout fed on large-bodied prey from the benthos and lake surface. Cladoceran zooplankton abundance may be regulated by kokanee. And kokanee growth and reproductive success may be influenced by the availability of Daphnia pulicaria, which was absent in zooplankton samples collected annually from 1990 to 1995, and after 1999. Distribution and diel migration of kokanee varied over the duration of the study and appeared to be most closely associated with prey availability, maximization of bioenergetic efficiency, and fish density. Rainbow trout were less abundant than were kokanee and exhibited less variation in population demographics, distribution, and food habits. There is some evidence that the population dynamics of rainbow trout were in-part related to the availability of kokanee as prey.     

Plasma ghrelin levels in rainbow trout in response to fasting, feeding and food composition, and effects of ghrelin on voluntary food intake

Ghrelin, a peptide hormone which stimulates growth hormone (GH) release, appetite and adiposity in mammals, was recently identified in fish. In this study, the roles of ghrelin in regulating food intake and the growth hormone (GH)-insulin-like growth factor I (IGF-I) system of rainbow trout (Oncorhynchus mykiss) were investigated in three experiments: 1) Pre- and postprandial plasma levels of ghrelin were measured in relation to dietary composition and food intake through dietary inclusion of radio-dense lead-glass beads, 2) the effect of a single intraperitoneal (i.p.) injection with rainbow trout ghrelin on short-term voluntary food intake was examined and 3) the effect of one to three weeks fasting on circulating ghrelin levels and the correlation with plasma GH and IGF-I levels, growth and lipid content in the liver and muscle was studied. There was no postprandial change in plasma ghrelin levels. Fish fed a normal-protein/high-lipid (31.4%) diet tended to have higher plasma ghrelin levels than those fed a high-protein/low-lipid (14.1%) diet. Plasma ghrelin levels decreased during fasting and correlated positively with specific growth rates, condition factor, liver and muscle lipid content, and negatively with plasma GH and IGF-I levels. An i.p. ghrelin injection did not affect food intake during 12-hours post-injection. It is concluded that ghrelin release in rainbow trout may be influenced by long-term energy status, and possibly by diet composition. Further, in rainbow trout, ghrelin seems to be linked to growth and metabolism, but does not seem to stimulate short-term appetite through a peripheral action.     

Identification, cloning and tissue localization of a rainbow trout (Oncorhynchus mykiss) intelectin-like protein that binds bacteria and chitin

Intelectins are a recently identified group of animal lectins involved in innate immune surveillance. This paper describes the primary structure, expression and immunohistochemical localization of a rainbow trout plasma intelectin (RTInt). RTInt exhibited calcium-dependent binding to N-acetylglucosamine (GlcNAc) and mannose conjugated Toyopearl Amino 650 M matrices. When GlcNAc eluates from chromatography matrices were analyzed by reducing 1D PAGE and Western blots, the lectin appeared as approximately 37 kDa and approximately 72 kDa bands. Similar analysis of plasma revealed a single 72 kDa band under reducing conditions. MALDI-TOF MS demonstrated five, approximately 37 kDa isoforms (pI 5.3-6.1) separated by 2D-PAGE. A 975 bp cDNA sequence obtained by RT-PCR from liver and spleen tissue encoded a 325 amino acid secretory protein with homology to human and murine intelectins, which bind bacterial components and are induced during parasitic infections. Gene expression and immunohistochemistry detected RTInt in gill, spleen, hepatic sinusoid, renal interstitium, intestine, skin, swim bladder and within leukocytes. Direct binding assays demonstrated the ability of RTInt to bind relevant bacterial and chitinous targets. These findings suggest that RTInt plays a role in innate immune defense against bacterial and chitinous microbial organisms.     

Status and opportunities for genomics research with rainbow trout

The rainbow trout (Oncorhynchus mykiss) is one of the most widely studied of model fish species. Extensive basic biological information has been collected for this species, which because of their large size relative to other model fish species are particularly suitable for studies requiring ample quantities of specific cells and tissue types. Rainbow trout have been widely utilized for research in carcinogenesis, toxicology, comparative immunology, disease ecology, physiology and nutrition. They are distinctive in having evolved from a relatively recent tetraploid event, resulting in a high incidence of duplicated genes. Natural populations are available and have been well characterized for chromosomal, protein, molecular and quantitative genetic variation. Their ease of culture, and experimental and aquacultural significance has led to the development of clonal lines and the widespread application of transgenic technology to this species. Numerous microsatellites have been isolated and two relatively detailed genetic maps have been developed. Extensive sequencing of expressed sequence tags has begun and four BAC libraries have been developed. The development and analysis of additional genomic sequence data will provide distinctive opportunities to address problems in areas such as evolution of the immune system and duplicate genes.     

Splenic cultures from rainbow trout,Oncorhynchus mykiss: establishment and characterisation

This study describes the culture conditions and the phenotypic features of different types of splenic cultures established from explants. Using the same culture technique it was possible to grow splenic explants from which monolayers of reticular origin, long-term haematopoietic cultures, and subcultures were obtained. The cultures were characterised by light and electron microscopy, cytochemical and immuno-cytochemical analyses, phagocytic activity and susceptibility to virus. The cultures comprised multilayers of epithelioid and fibroblastoid cells with haemopoietic foci, melanomacrophages and eosinophilic granular cells. The cytochemical and immuno-cytochemical analyses revealed that the stromal cells were always positive for ANAE activity. The stromal cells in primary cultures were negatively or weakly stained by antibodies directed against cytokeratins and S-100, but in the subcultures they were strongly stained by these antibodies. The stromal cells had very poor phagocytic activity and were susceptible to VHS virus.     

Isolation and characterization of the receptor for vitellogenin from follicles of the rainbow trout,Oncorhynchus mykiss

The isolation and characterization of the receptor for vitellogenin from follicle membranes of the rainbow trout, Oncorhynchus mykiss, is described. Follicle membrane proteins subjected to SDS-polyacrylamide gel electrophoresis and subsequently to either protein staining or ligand blotting with radiolabelled vitellogenin (¹²⁵iodine-vitellogenin) demonstrated that the vitellogenin receptor has an apparent molecular mass of 200 kD (probably comprising of two 100-kD subunits) under non-reducing conditions. The vitellogenin binding sites were identified as specific receptors: binding was saturable and the binding sites were both tissue specific to follicle membranes and exhibited ligand specificity. Scatchard analyses of specific binding data revealed a single class of binding sites with a high affinity for rainbow trout vitellogenin (K _d=8.2·10^-9 mol·1^-1). Both brown trout, Salmo trutta, vitellogenin and carp, Cyprinus carpio, vitellogenin were able to displace the radiolabelled rainbow trout vitellogenin from its receptor, although they were less effective than rainbow trout vitellogenin.Abbreviations B _max maximum number of binding sites available - BSA bovine serum albumin - bt-VTG brown trout vitellogenin - c-VTG earp vitellogenin - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - K _d dissociatian constant - NCM nitrocellulose membranes - PMSF phenylmethylsulphonylfluoride - rt-VTG rainbow trout vitellogenin - VTG vitellogenin     

Changes in expression of provasotocin and proisotocin genes during adaptation to hyper- and hypo-osmotic environments in rainbow trout

Summary The physiological roles of neurohypophysial hormones, vasotocin (VT) and isotocin (IT), are not yet clear in teleosts. Since information on responsiveness of hypothalamic neurosecretory neurons to environmental stimuli may contribute to an understanding of their physiological roles, effects of environmental hyper- and hypo-osmotic stimuli on expression of VT and IT precursor (proVT and proIT) genes in rainbow trout were investigated, using an in situ hybridization technique in which 46 mer synthetic oligonucleotides were used as hybridization probes. The probes corresponded to the mRNA loci encoding chum salmon proVT (-5 to 11) and proIT (-5 to 11), and were labeled at the 3-end with ³⁵S. Autoradiographic silver grains which represent the hybridization signals of proVT and proIT mRNAs were localized in both magnocellular and parvocellular neurons in the nucleus preopticus magnocellularis (NPOmg). Localizations of proVT and proIT hybridization signals coincided with those of VT- and IT-immunoreactive neurons in adjacent sections, and showed that proVT and proIT genes are expressed in separate neurons. The intensity of proVT hybridization signals as determined by grain counting in magnocellular neurons in the NPOmg was conspicuously decreased after transfer from fresh water (FW) to 80% seawater (SW). The proVT mRNA levels in SW trout were consistently lower than those of FW trout for up to 2 weeks. After return from 80% SW to FW, the proVT mRNA level increased, attaining the initial FW level. The proIT mRNA levels in SW trout were not statistically different from those in FW trout, except for the 1st day after transfer to SW. These results suggest that synthesis of proVT was elevated by transfer from higher to lower salinity, and that VT may have a physiological role in salmonid osmoregulation, especially in adaptation to a hypo-osmotic environment.Abbreviations ABC avidin-biotin-peroxidase complex - AVP arginine vasopressin - BSA bovine serum albumin - EDTA ethylene diamine tetra-acetic acid - cpm counts per minute - FW fresh water - GFR gromerular filtration rate - ISH in situ hybridization - IT isotocin - mRNA messenger ribonucleic acid - NPOmg nucleus preopticus magnocellularis - OXT oxytocin - PBS phosphate-buffered saline - SSC saline sodium citrate - RT room temperature - SW seawater - VT vasotocin     

Acidosis,glycolysis and energy state in anaerobic heart tissue from rainbow trout

With focus on metabolism not depending on contractility in myocardial tissue from rainbow trout, Oncorhynchus mykiss, the effects of high CO₂ on lactate production, phosphocreatine, creatine, ATP, ADP, AMP and intracellular pH were examined under a blockage of cell respiration either alone or in combination with a glycolytic inhibition. Irrespective of metabolic interventions, a change in CO₂ from 1 to either 11 or 5% of the gas mixture perfusing the muscle bath with 15 mmol·l^-1 HCO _- ³ caused a drop of intracellular pH from 7.4 to either 6.5 or 7.0, respectively. An elevation of CO₂ to 11% diminished the rate of anaerobic lactate formation and slightly lowered anaerobic energy degradation. The further addition of 1 mmol·l^-1 iodoacetate to inhibit glycolysis strongly enhanced the tendency of acidosis to lower energy degradation. Moreover, iodoacetate induced a parallel decrease in ATP and total concentration of phosphorylated adenylates and an increase in resting tension. These effects were all substantially dampened by acidosis and could not immediately be related to tissue content of energy-rich phosphates. Tentatively, the depression of resting tension was the prime effect and a cause of the other effects acidosis. However, these were not affected by an inhibition of resting tension development with 2,3-butadione monoxime. The results suggest that glycolysis protects the anaerobic myocardium also by means not immediately related to tissue energy state. Acidosis exerts a similar protection, which is marginal as long as glycolysis is fully active, but substantial with an inhibited glycolysis.Abbreviations Cr _t total tissue concentration of creatine - G _PCr energy liberated per mol PCr hydrolyzed - IAA iodoacetate - PCr phosphocreatine - PE total tissue concentration of energy-rich phosphate bonds - pH _i intracellular pH - P _i inorganic phosphate - TAN total tissue concentration of phosphorylated adenylates - 2,3-BDM 2,3-butadione monoxime - SE standard error of the mean     

Evidence for multiple adrenoceptor sites in rainbow trout vasculature

The importance of neuronal and lumenal vascular adrenoceptors in the regulation of vascular reactivity was examined in rainbow trout (Oncorhynchus mykiss), in vivo and in vitro. In vivo, ganglionic blockade with hexamethonium or -adrenoceptor blockade, with either phentolamine or prazosin, produced similar (7 mmHg) decreases in dorsal aortic blood pressure. The drop in dorsal aortic pressure produced by phentolamine or prazosin was due to reduced systemic vascular resistance. Neither the -adrenoceptor antagonist, phenoxybenzamine nor chemical sympathectomy with 6-hydroxy-dopamine affected dorsal aortic pressure. However, after chemical sympathectomy, phenoxybenzamine lowered dorsal aortic pressure to levels similar to that produced by either phentolamine or prazosin. Plasma epinephrine and norepinephrine concentrations increased four- and twofold, respectively, in sympathectomized fish. Sympathectomy also produced a leftward shift in the epinephrine dose/response curve of the in vitro perfused splanchnic vasculature, placing the effective catecholamine concentration well within the in vivo plasma levels. These results indicate that following chemical sympathectomy arterial blood pressure is stabilized by circulating catecholamines through the combined effect of increased plasma catecholamine concentrations and increased sensitivity of vascular adrenoceptors. Phenoxybenzamine is incapable of blocking neuronal vascular adrenoceptors but is a potent antagonist of the up-regulated adrenoceptors, suggesting that the latter are localized on the lumenal side of the vessel.Abbreviations 6OH-DA 6-hydroxy dopamine - EC ₅₀ half-maximal response - EDTA ethylenediaminetetra-acetate - PE polyethylene - PBS phosphate-buffered saline - P _da dorsal aortic pressure - USP United States Pharmacopeia     

Rainbow trout (Oncorhynchus mykiss) sIgM- leucocytes secrete an interleukin-2 like growth factor after mitogenic stimulation in vitro

Two secreted proteins were detected in culture supernatants of PHA or PMA stimulated, immunomagnetically separated, sIgM(-) leucocytes of rainbow trout (Oncorhynchus mykiss) with 60kDa and with 12-15kDa (multiple bands). So called conditioned media (CM), containing these proteins, induced significant activation of blood and head kidney leucocytes. Immunomagnetically separated, naive as well as PHA activated sIgM(-) T lymphocytes and LPS prestimulated sIgM(+) B lymphocytes could be identified to be responding to these secreted proteins. Using a monoclonal antibody specific for mouse IL-2 (clone JES6-1A12), one of the multiple 12-15kDa proteins could be stained in Western blots. It was also shown that the induced proliferation was due to this protein in the CM, as the same anti-IL-2 mab was able to block the CM induced proliferation. Furthermore, survival of the IL-2 dependent mouse cell line HT-2 was enhanced after addition of various concentrations of CM. The data presented show, for the first time, that mitogen stimulated trout sIgM(-) leucocytes secrete a cytokine like growth factor sharing functional and structural similarities with mammalian IL-2.     

Effect of temperature and temperature acclimation on the ryanodine sensitivity of the trout myocardium

The influence of acute temperature change and temperature acclimation on the sensitivity of contracture development to ryanodine were examined in the rainbow trout myocardium using two preparations: in vitro isolated ventricular strips and in situ working perfused hearts. Ryanodine effects in vitro were dependent on test temperature (8 and 18 °C), pacing frequency (0.2–1.5 Hz) and acclimation temperature (8 and 18 °C). At a pacing frequency of 0.2 Hz and a test temperature of 18 °C, ryanodine depressed isometric tension development in ventricular strips both from trout acclimated to 8 and 18 °C but the decrease was significantly greater in strips from 8 °C-acclimated trout. No ryanodine effect was observed in either acclimation group at a test temperature of 8°C. The effect of ryanodine in vitro was reduced or lost at pacing frequencies greater than 0.2 Hz and at 0.6 Hz ryanodine depressed tension development at 18 °C only in strips from 8 °C-acclimated trout. Ryanodine did not affect tension development at stimulation rates above 0.6 Hz in any test group. Likewise, ryanodine did not significantly impair cardiac performance of in situ working perfused heart preparations which operated at intrinsic beat frequencies in excess of 0.6 Hz. These results suggest that the sarcoplamic reticulum calcium release channel of the trout myocardium is expressed but is not functionally involved in beat-to-beat regulation of contractility at either (1) low temperature (8 °C), or (2) at routine physiological heart rate (>0.6 Hz). However, under conditions in which involvement of the sarcoplasmic reticulum is observed (18 °C and a heart rate < 0.6 Hz), prior acclimation to low temperature results in either a greater capacity of the sarcoplasmic reticulum to store releasable calcium or an increase in the amount of calcium that is in releasable form.Abbreviations bm body mass - E-C coupling, excitation-contraction coupling - IVS isometric ventricular strip - SR sarcoplasmic reticulum - TES N-tris[hydroxy-methyl]methyl-2-aminoethane sulfonic acid - WPH in situ working perfused heart     

The effect of exogenous catecholamines on the ventilatory and cardiac responses of normoxic and hyperoxic rainbow trout,Oncorhynchus mykiss

Ventilation frequency, opercular pressure amplitude, heart rate, dorsal aortic pressure, arterial pH, arterial O₂ tension, and plasma catecholamine levels were recorded in rainbow trout, Oncorhynchus mykiss, during normoxia (19.7 kPa, 148 mmHg) or hyperoxia (51.2 kPa, 384 mmHg) after injection of various concentrations of catecholamines. In normoxic fish, adrenaline injection resulted in a depression of arterial O₂ tension, hypoventilation due to a drop in ventilation frequency, and a drop in heart rate, while dorsal aortic pressure increased. Noradrenaline depressed ventilation frequency, but opercular pressure amplitude increased to a far greater extent, and dorsal aortic pressure increased. During hyperoxia, adrenaline injection lowered ventilation frequency, opercular amplitude and heart rate, but dorsal aortic pressure increased. The stimulatory effects of noradrenaline on ventilation were abolished during hyperoxia, but the cardiac responses were similar to those seen during normoxia. These results indicate that catecholamines can modify the ventilatory output from the respiratory centre, and modification of ventilation frequency can occur independently of opercular pressure amplitude.Abbreviations f _g ventilation frequency - HPLC high performance liquid chromatography - P _op opercular pressure amplitude - f _h heart rate - P _DA dorsal aortic pressure - pH_a arterial pH - P _aO₂ arterial oxygen tension - PO₂ oxygen tension