Somatostatin sst2 receptors inhibit peristalsis in the rat and mouse jejunum

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Abstract
Somatostatin [somatotropin release-inhibitory factor (SRIF)] has widespread actions throughout the gastrointestinal tract, but the receptor mechanisms involved are not fully characterized. We have examined the effect of selective SRIF-receptor ligands on intestinal peristalsis by studying migrating motor complexes (MMCs) in isolated segments of jejunum from rats, mice, and sst2-receptor knockout mice. MMCs were recorded in 4- to 5-cm segments of jejunum mounted horizontally in vitro. MMCs occurred in rat and mouse jejunum with intervals of 104.4 ± 10 and 131.2 ± 8 s, respectively. SRIF, octreotide, and BIM-23027 increased the interval between MMCs, an effect fully or partially antagonized by the sst2-receptor antagonist Cyanamid154806. A non-sst2 receptor-mediated component was evident in mouse as confirmed by the observation of an inhibitory action of SRIF in sst2 knockout tissue. Blocking nitric oxide generation abolished the response to SRIF in rat but not mouse jejunum. sst2 Receptors mediate inhibition of peristalsis in both rat and mouse jejunum, but a non-sst2component also exists in the mouse. Nitrergic mechanisms are differentially involved in rat and mouse jejunum.