Motor activity in decerebrate rats: spontaneous and nutrient-induced changes

Bilateral decerebration was performed in adult Wistar rats of either sex under pentobarbital sodium anesthesia. Decerebrate rats were aphagic and adipsic and received 44 kcal/day subcutaneously by gastric intubation. Their motor activity was recorded in the morning after an 18-h fast, following various treatments: 10 ml mash (22 kcal) or 3.6 g glucose/kg; intragastric, intraperitoneal, or subcutaneous injection of glucose (3.6 g/kg) or glycerol (1.84 g/kg); or injection of epinephrine (25 micrograms/kg ip or im). These treatments were also applied to control rats previously maintained in the same conditions. Motor activity of both operated and control rats was generally reduced in a similar manner: intragastric mash greater than intraperitoneal glucose = intraperitoneal glycerol greater than or equal to intragastric glucose greater than intraperitoneal epinephrine. Subcutaneous glucose and glycerol and intramuscular epinephrine produced hyperactivity, at least for the first 30 min. Thus decerebrate rats respond like normal rats by reducing their general activity when subjected to the same satiating treatments given intragastrically or intraperitoneally. This suggests that the brain stem of rats can monitor peripheral information regarding caloric replenishment.