An anesthetic dose of 50 mg/kg (i.p.) sodium pentobarbital caused a 61% increase in blood glucose levels in mice. Nicotine (2.5 mg/kg) given intraperitoneally 15 min prior to the sodium pentobarbital treatment further increased hyperglycemia by 29% over pentobarbital alone and 90% higher than the control. Mecamylamine (0.5 mg/kg) given intraperitoneally 15 min prior to nicotine resulted in blood glucose concentrations near the control value. Atropine (2 mg/kg) administered intraperitoneally did not prevent the hyperglycemia induced by nicotine and pentobarbital. No significant correlation was observed between the sleep time and the blood glucose of the unconscious or awake mice. However, a significant correlation was observed between the blood glucose concentration of the sleeping and awake mice. Blood glucose levels were always higher when the neuronal activity was depressed and were lower when the neuronal activity was increased.