Peripheral anti-muscarinic effects of olanzapine and risperidone. A) Prolonged (60 sec) electrical stimulation of the cut distal end of the pelvic nerve results in a bladder contraction. The amplitude of the initial rise of the contraction (Phase I) is resistant to muscarinic blockade. The plateau phase (Phase II), however, is very sensitive to anti-muscarinic agents. After 10 mg/kg of olanzapine, Phase I is somewhat decreased, but phase II is markedly reduced. After 10 mg/kg of risperidone, Phase I is larger than control, while phase II is unchanged. B) Phase I amplitude as a function of cumulative doses of olanzapine and risperidone. Olanzapine decreased the amplitude at 1 and 10 mg/kg. Risperidone did not reduce the amplitude but it significantly increased the amplitude at 10 mg/kg. C) Phase II amplitude was markedly reduced by 1 and 10 mg/kg of olanzapine whereas risperidone had no effect. * = p < 0.05; ** = p < 0.01.