Time sharing of heart power: Cardiovascular adaptations to food-arousal inAplysia

Abstract

1. Food stimuli have been shown previously to elicit inAplysia an arousal state characterized by an increased tendency to bite and an increased strength of bitting. These overt behavioral changes have also been correlated with an increase in heart rate. 2. In the present study, we show that systemic blood pressure increases two-fold during food arousal. Blood flow through the artery that supplies the head is also increased about two-fold. Pressure and flow both increase within 1–2 min of food presentation, and both decay back to their baseline values within about five minutes after removal of the food stimulus. 3. Unlike the increase in heart rate during food arousal, the increases in blood pressure and blood flow are independent of the degree of satiation of the animal. 4. The increase in blood pressure during food arousal is neurally mediated. 5. During rhythmic biting, the vascular resistance of the abdominal and anterior aortae vary in an alternating pattern that is phase-locked to the biting cycle. This pattern of resistance changes is such that blood flow to digestive organs is maximal during the retraction phase of biting, whereas flow to the head is maximal during the protraction phase. 6. The increase in resistance of the abdominal aorta during protraction is mediated by neuronal input to vasoconstrictor muscle. 7. Strongly reducing blood flow to the head for even a few minutes significantly impairs the efficiency of biting movements.