Fig 4. Uncoupling of Ca²⁺ transients between SMC and ICC resulting in reduced intestinal contractility in Srf KO mice.

(A) Ca²⁺ transients recorded from several longitudinal SMC (LM) and ICC-MY in WT and KO jejunum within a field of view. Note that Ca²⁺ transients in ICC-MY (overlay of ICC-MY1-3) occur almost synchronously in WT and KO. Ca²⁺ transients in ICC-MY and LM are in phase in WT muscles (overlay of ICC-MY1 and LM1). Reduced coupling and greater latency was observed between the Ca²⁺ transients in ICC-MY and SMC in KO muscles (overlay of ICC-MY2 and LM2). (B) Frequency of Ca²⁺ transients in intestinal LM, frequency of Ca²⁺ transients in ICC-MY, and latency between Ca²⁺ transients in ICC-MY and LM of WT and KO mice are shown in graphs. (C) Contractions of WT and KO duodenal and jejunal muscles measured before and after L-NNA (100 μm) and atropine (1 μm). (D) Comparison of jejunal contractile amplitudes and summary of L-NNA and L-NNA plus atropine effects on jejunal contractions in WT and KO (expressed as percentages of control activity, i.e., no drugs present; areas under the curve for WT or KO in C). * p ≤ 0.5, n = 5