Acute and chronic cold exposure differentially affect cardiac control, but not cardiorespiratory function, in resting Atlantic salmon (Salmo salar)

• Published in: Current Research in Physiology
• Main Authors: Porter, E.S., Clow, K.A., Sandrelli, R.M., Gamperl, A.K.
• Format: Text
• Language: English
• Published: Elsevier 2022
• Subjects: Articles from the special issue: Environment and the Heart; edited by Holly Shiels; Todd Gillis; Erica Eliason; Elena Fabbri and Denis Abramochkin; Todd; Atlantic salmon; Salmo salar
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8960890/; https://doi.org/10.1016/j.crphys.2022.03.002

No studies have examined the effects of cold temperatures (∼0–1 °C) on in vivo cardiac function and control, and metabolism, in salmonids. Thus, we examined: 1) how acclimation to 8 °C vs. acclimation (>3 weeks) or acute exposure (8-1 °C at 1 °C h(−1)) to 1 °C influenced cardiorespiratory parameters in resting Atlantic salmon; and 2) if/how the control of cardiac function was affected. Oxygen consumption ([Formula: see text]) and cardiac function [i.e., heart rate (f(H)) and cardiac output ([Formula: see text]] were 50% lower in the acutely cooled and 1(o)C-acclimated salmon as compared to 8 °C fish, whereas stroke volume (V(S)) was unchanged. Intrinsic f(H) was not affected by whether the fish were acutely exposed or acclimated to 1 °C (values ∼51, 24 and 21 beats min(−1) in 8 and 1 °C-acclimated fish, and 8-1 °C fish, respectively), and in all groups f(H) was primarily under adrenergic control/tone (cholinergic tone 13–18%; adrenergic tone 37–70%). However, β-adrenergic blockade resulted in a 50% increase in V(S) in the 1(o)C-acclimated group, and this was surprising as circulating catecholamine levels were ∼1–3 nM in all groups. Overall, the data suggest that this species has a limited capacity to acclimate to temperatures approaching 0 °C. However, we cannot exclude the possibility that cardiac and metabolic responses are evoked when salmon are cooled to ∼ 0–1 °C, and that this prevented further declines in these parameters (i.e., they ‘reset’ quickly). Our data also provide further evidence that V(S) is temperature insensitive, and strongly suggest that changes in adrenoreceptor mediated control of venous pressure/capacitance occur when salmon are acclimated to 1 °C.