Lactobacillus reuteri ingestion and IKCa channel blockade have similar effects on rat colon motility and myenteric neurones

P>Background We have previously shown that ingestion of Lactobacillus reuteri may modulate colonic enteric neuron activity but with unknown effects on colon motility. The aim of the present report was to elucidate the neuronal mechanisms of action of the probiotic by comparing the effects on motility of L. reuteri ingestion with blockade of a specific ionic current in enteric neurons. Methods We have used intraluminal pressure recordings from ex vivo rat colon segments and whole cell patch clamp recordings from neurons of rat longitudinal muscle myenteric plexus preparations to investigate the effects of L. reuteri and TRAM-34 on colon motility and neurophysiology. The effects of daily feeding of 109L. reuteri bacteria or acute application of TRAM-34 on threshold fluid filling pressure or pulse pressure was measured. Key Results Lactobacillus reuteri increased intraluminal fluid filling pressure thresholds for evoking pressure pulses by 51% from 0.47 +/- 0.17 hPa; the probiotic also decreased the pulse pressure amplitudes, but not frequency, by 18% from 3.91 +/- 0.52 hPa. The intermediate conductance calcium-dependent potassium (IKCa) channel blocker TRAM-34 (3 mu mol L-1) increased filling threshold pressure by 43% from 0.52 +/- 0.22 hPa and reduced pulse pressure amplitude by 40% from 2.63 +/- 1.11 hPa; contraction frequency was unaltered. TRAM-34 (3 mu mol L-1) reduced membrane polarization, leak conductance and the slow afterhyperpolarization current in 16/16 myenteric rat colon AH cells but 19/19 S cells were unaffected. Conclusions & Inferences The present results are consistent with L. reuteri enhancing tonic inhibition of colon contractile activity by acting via the IKCa channel current in AH cells.