Cardiovascular changes in the unanaesthetized lingcod (Ophiodon elongatus) during short-term, progressive hypoxia and spontaneous activity

Abstract

Cardiac output [Formula: see text] and arterial blood pressures in the ventral and dorsal aortae (PVAnd PDA) were measured directly and simultaneously in the lingcod. The branchial and systemic conductances to blood flow (Gg and Gs) were calculated. During progressive hypoxia [Formula: see text], Gg, Gs, PVA, and PDA were all reduced when the water [Formula: see text] decreased below 45 mmHg (1 mmHg = 133.322 Pa). Spontaneous activity was characterized by an initial bradycardia and concurrent reduction in [Formula: see text], Gg, Gs, PVA, and PDA. Longer periods of activity were subsequently followed by a period of restitution where [Formula: see text], Gg, Gs, PVA, and PDA were all elevated.The beat by beat oscillations in flow were usually synchronized with, and in the same direction as, those in vascular conductance during both activity and hypoxia. This synchrony was most apparent between Gs and [Formula: see text] during the rapid cardiovascular adjustments occurring with activity. It is suggested that the observed relationship between flow and conductance changes was a result of passive changes in conductance when flow was altered, plus an active component which involved reflex vasoactivity.