The effect of fasting on the methamphetamine and apomorphine-induced locomotor activities and on the metabolism of brain monoamines in the mouse.

Abstract

The effect of 24-h fasting on spontaneous motor activities, vertical (VMA), horizontal (HMA), and wheel running motor activity (WRA), induced by the administration of methamphetamine and apomorphine to male ddy mice, weighing 18-22g, was examined. Also the effect of 24-h fasting on the cage-climbing activity and the levels of brain monoamine-related substances was examined.

The results obtained are summarized as follows.

1)With fasting the VMA showed a marked increase but the HMA showed only a slight increase. No increase in the WRA was noted.

2)When methamphetamine (2mg/kg, s. c.) was administered to fasting mice, the VMA increased significantly more than that of mice which were fed, regardless of pretreatment with or without haloperidol (0.025mg/kg, s. c.). When fasting mice were pretreated with haloperidol, the HMA decreased slightly and the WRA increased slightly although the HMA and WRA in fasting mice showed the same patterns as those of mice which were fed and pretreated without haloperidol.

3)When apomorphine (0.1 and 0.5mg/kg, s. c.) was administered to fasting mice, all the VMA, HMA and WRA decreased at an early stage during the experiment regardless of pretreatment with or without haloperidol. The same results were noted in mice which were fed.

4)The cage climbing activity in fasting mice receiving apomorphine at 1mg/kg, s. c. showed the some pattern as that of mice which were fed.

5)When measuring brain monoamine-related substances in fasting mice, using the HPLC-ECD method, the concentrations of DA, NE, 5-HT and 5-HIAA in the corpus striatum increased and 3-MT decreased. The concentration of MHPG in the hypothalamus increased, and the concentration of 3-MT in the nucleus accumbens decreased.

These results suggest that fasting may modify the activities of the central dopaminergic, adrenergic and serotonergic neurons.