OBJECTIVE:

To observe whether the motilin receptor (MTLR) can be expressed in primarily cultured myenteric neurons of rats and investigate the mechanism of motilin induced Ca2+ signaling in myenteric neurons of rats.

METHODS:

Expression of the motilin receptor was identified with double-immunofluorescence staining technique. Data on the intracellular Ca2+ concentration ([Ca2+]i) of cultured myenteric neurons with different treatments were collected by measuring Ca2+ fluorescent intensity (FI) in each neuron under confocal microscope.

RESULTS:

The cultured myenteric neurons showed positive motilin receptor immunoreactivity. In Hank's solution, 10(-6) mol/L motilin could elevate [Ca2+]i, its height of peak being 30.6 +/- 3.7 and its FI relative change percentage being (100. 8 +/- 18.4)%. In D-Hank's solution (after removal of extracellular Ca2+, or after treatment with verapamil,an L-type calcium channel blocker), motilin could induce a small increase of [Ca2+]i. After pretreatment with NEM,a G protein inhibitor, and Compound 48/80, a PLC inhibitor, in Hank's solution respectively, motilin was inhibited and the [Ca2+]i was significantly lower than that of the group to which was added only motilin (P < 0.05). After pretreatment with D-sphingosine, a PKC inhibitor, the effect of motilin was not significantly different from that of the group to which was added only motilin (P > 0.05).

CONCLUSION:

The motilin receptor could be expressed by cultured myenteric neurons of rats. Motilin could increase [Ca+]i. The increase of [Ca2+]i was caused by release of intracellular stores and influx of extracellular Ca2+, mainly through the L-type calcium channel. The motilin receptor-coupled G-protein, PLC and IP3 pathway participated in the release of Ca2+ from intracellular stores.