| Popis: |
We examined whether infant rats would display a diurnal variation in antinociception that was produced by oral infusion of nutritive and nonnutritive fluids. Ten-day-old pups were assigned to one of four fluid conditions (milk, sucrose, saccharin, and water) or one of three conditions that controlled for the stress of the infusion procedure, either during the dark or during the light. Longer paw lift latencies were observed under dark than under light conditions in all control conditions and in most fluid-infusion conditions, indicating that antinociception is influenced by diurnal variables in the 10-day-old rat. Saccharin, milk, and water were effective in elevating paw lift latencies, but sucrose was not, indicating that the nutritive value of fluids is less important than flavor in producing antinociception. The antinociceptive effects of the diurnal cycle and the infused fluids appeared to be additive. |
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