Daily Epinephrine but not Norepinephrine Administration Produces Anticipatory Drinking Behavior in Rats

Abstract

Peripheral oscillators, especially in the liver, are thought to be part of the food entrained oscillator (FEO). The internal mediating signals involved in food entrainment are unknown. Catecholamines may be one signal, since they increase their blood concentration immediately after feeding, and their intraperitoneal (IP) administration produces hyperglycemia and a satiety response by their direct effect on the liver. The present study explored the role of epinephrine (EPI) and norepinephrine (NE) as entraining signals to the FEO. This effect was explored by daily IP administration of EPI (12.5 µg/100 g bw), NE (25 µg/100 g b) or vehicle on rhythmicity of drinking behavior in rats maintained under constant conditions. Behavioral effects were compared with those observed in a group entrained with a restricted feeding schedule (RFS). IP administration of EPI produced anticipatory drinking behavior, in a dosedependent manner but with a lower intensity than that produced by RFS. In contrast, daily NE or vehicle administration did not produce any changes in drinking rhythmicity. None of the manipulations produced effects on the SCN-dependent freerunning period. Present data suggest a role of EPI as a factor involved with the internal mediating signal for FEO; however, other preabsortive or postabsortive signals may also be part of this complex entraining pathway.