The dual effect of BAY K 8644 on excitation-contraction coupling in gastric smooth muscle

1. BAY K 8644 at concentrations of 10(-10)-10(-6) M had a stimulant effect on the spontaneous electrical and contractile activity of smooth muscle preparations from cat and guinea pig stomach. 2. Nifedipine (10(-6) M) antagonized the BAY K 8644-induced spike potentials and the related phasic contractions. 3. Neither the excitatory nor the inhibitory effect of BAY K 8644 was significantly influenced by atropine (10(-7) M), phentolamine (10(-7) M), propranolol (10(-7) M) or TTX (10(-6) M). 4. TEA (10(-3) M) abolished the inhibitory effect of BAY K 8644 on the spike generation and increased the amplitude of the phasic contractions.