Muscular effects of orexin A on the mouse duodenum: mechanical and electrophysiological studies

Nerve-mediated influences on gastrointestinal motility in response to orexin A, either centrally injected or applied to isolated gut preparations, have been reported. However, the presence of orexin receptors at the gastrointestinal smooth muscle level has been found. On these grounds, in the present study we evaluated whether orexin A also exerts direct muscular effects in the duodenal smoothmuscle of themouse in an attempt to explain the possible mechanism of action involved. The experimental results frommechanical and electrophysiological studies indicate that orexin A causes direct contractile responses in the isolated preparations and evokes changes in the ionic currents of the smooth muscle cells. Thus, orexin A, in addition to its neutrally mediated influences on gastrointestinal motility, exerts direct muscular effects on the mouse duodenum. This latter mechanism, from a physiological point of view, may act in a synergic manner to reinforce the neuronal signals.