Figure 4. Effects of hexamethonium and UK14,304 applied to the organ bath on the amplitudes of ascending contractile responses.

□, control responses; ▪, responses in the presence of a drug; , responses following washout. As for all subsequent column graphs, column heights represent mean response amplitudes while error bars indicate s.e.m. Effect of hexamethonium (A; 100 μm, n = 4) and UK14,304 (B; 100 nm, n = 7) on ascending responses to transmural stimulation in both the longitudinal and circular muscle layers in intact segments of intestine. Responses in both layers were abolished by both drugs. † Significant difference from control, P < 0.005. C, effect of UK14,304 on ascending contractions of the circular muscle evoked by distension in the opened intestinal preparation. Reflex responses were virtually abolished in the presence of the drug (n = 4, *P < 0.02).