Aim: Contrasting results concerning the influence of obestatin on gastric motility have been reported. In the present experiments we investigated the effects of obestatin on the motor responses in strips from the mouse gastric fundus. Electrophysiological records in a single smooth muscle cell were also performed.

Methods: Gastric longitudinal strips from the fundus region were mounted in organ baths for isometric recording of the mechanical activity. Electrical field stimulation (EFS) was applied via two platinum wire rings. Voltage dependent ionic currents were recorded in current- and voltage-clamp conditions by single microelectrode inserted in a gastric smooth muscle cell.

Results: At basal tension, EFS (4–16 Hz) elicited contractile responses that were abolished by TTX or atropine and not influenced by guanethidine. Addition of obestatin to the bath medium caused a slight decrease of the basal tension and a reduction in amplitude of the EFS-induced contractile responses. The former effect was TTX-insensitive. Obestatin also reduced the amplitude of the response to DMPP whereas did not influence that to methacholine. In the presence of L-NNA, obestatin still depressed the amplitude of the EFS-induced contractile responses. In carbachol precontracted strips obestatin still decreased the basal tension but did not influence the amplitude of the neurally-induced NANC relaxations. Preliminary electrophysiological results showed that obestatin slightly affected the membrane properties and ionic currents.

Conclusions: These results indicate that obestatin, other than acting on gastric smooth muscle, modulates, at the postganglionic site, the cholinergic neurotransmission.