Changes in plasma catecholamine concentration during salinity manipulation and anaesthesia in the hagfish <Emphasis Type="Italic">Eptatretus cirrhatus</Emphasis>

Plasma catecholamines were measured following surgery under anaesthesia and after exposing hagfish to 90 and 110% sea water (SW). Plasma noradrenaline (NA) concentration increased from a resting value of 7 to 818 nM l⁻¹ on anaesthesia. Plasma adrenaline (AD) did not change. NA concentrations also increased during volume depletion (110% SW), but to much lower values (26 nM l⁻¹ at 100 min). AD concentrations were increased at 20 min, then fell. During volume loading (90% SW) NA fell, and AD increased to a maximum concentration of 511 nM l⁻¹ at 40 min (resting concentration 24 nM l⁻¹). The data are consistent with a vasoconstrictory role for NA on central veins when venous pressures fall and a vasodilatory role for AD on volume expansion.