Differential effects of central and peripheral cholinergic blockade on water consumption by rats.

Atropine (5 mg/kg, s.c., twice daily) had no significant effect on 24-h water consumption on day 1 of treatment; on subsequent days the rats showed a significant increase. Procyclidine (5 mg/kg, s.c., twice daily) had a similar effect, except that the increase in daily water consumption began on the third day of treatment. Methylatropine (5 mg/kg, s.c., twice daily) markedly depressed water consumption on day 1; from the second day on no significant effects on 24-h water consumption were seen. The results suggest that the dipsogenic actions of cholinergic blocking agents on 24-h water consumption involve central rather than purely peripheral actions.