Fig. 5.
Activation of CaSR by R-568 attenuates the effect of TTX to reduce cAMP-stimulated Isc in the colon. A: representative recording of Isc responses to sequential additions of forskolin and R-568 in the absence of TTX in a rat distal colon segment. Following additions of 500 nM forskolin to mucosal and serosal solutions, 10 μM of R-568 was added to serosal solution to activate CaSR activity. B: quantitative changes in Isc following treatment with forskolin ± R-568 in the proximal and distal colons. C: representative recording of Isc responses to sequential additions of forskolin and R-568 in the presence of TTX in a rat distal colon segment. Following additions of 500 nM forskolin to mucosal and serosal solutions, 10 μM of R-568 was added to serosal solution to activate CaSR activity. D: quantitative changes in Isc following treatment with forskolin ± R-568 in the proximal and distal colons. E summarizes the ΔIsc induced by R-568 in the absence and presence of TTX.