Baroreflex responses to activity at different temperatures in the South American rattlesnake, Crotalus durissus

AbstractIn humans, physical exercise imposes narrower limits for the heart rate (fH) response of the baroreflex, and vascular modulation becomes largely responsible for arterial pressure regulation. In undisturbed reptiles, the baroreflex-relatedfH alterations at the operating point (Gop) decreases at elevated body temperatures (Tb) and the vascular regulation changes accordingly. We investigated how the baroreflex of rattlesnakes,Crotalus durissus, is regulated during an activity at differentTb, expecting that activity would reduce the capacity of the cardiac baroreflex neural pathway to buffer arterial pressure fluctuations while being compensated by the vascular neural pathway regulation. Snakes were catheterized for blood pressure assessment at three differentTb: 15, 20 and 30  °C. Data were collected before and after activity at eachTb. Baroreflex gain (Gop) was assessed with the sequence method; the vascular limb, with the time constant of pressure decay (τ), using the two-elementWindkessel equation. BothGop andτ reduced whenTb increased. Activity also reducedGop andτ in allTb. The relationship betweenτ and pulse interval (τ/PI) was unaffected by the temperature at resting snakes, albeit it reduced after activity at 20  °C and 30 °C. The unchangedτ/PI and normalizedGop at differentTb indicated those variables are actively adjusted to work at differentfH and pressure conditions at rest. Our data suggest that during activity, the baroreflex-relatedfH response ...
Source: Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology - Category: Physiology Source Type: research