Fig. 2.

Microinjection of apelin-13 into the dorsal vagal complex (DVC) induces a dose-dependent inhibition of gastric tone and motility. A: representative traces showing the response of the antrum to microinjections of 1–100 pmol apelin-13 in the DVC. Oblique parallel lines designate a 3–5-min time interval. B: schematic representation of microinjection sites. Left: approximate boundaries of dorsal motor nucleus of the vagus (DMV) and hypoglossal nucleus (HGN) are indicated with dashed curves in bright-field view. Right: ●, brain stem microinjection sites performed in caudal, intermediate, and rostral DVC. For simplicity, not all the injection sites are included. X, sites of injection outside the DMV that did not induce any gastric motor response. AP, area postrema; CC, central canal; NTS, nucleus tractus solitarius; 4V, fourth ventricle. C: graphic representation showing the dose-response curve for gastric motility following apelin-13 microinjection in the DVC. D: graphic representation showing the dose-response curve for gastric tone following apelin-13 microinjection in the DVC. E: graphic summary of the duration of dose-dependent alterations in gastric motor function following apelin-13 (1–300 pmol) microinjection (n = 16). The duration was defined as the postinjection time period in which contraction amplitude was accompanied by decreased tone. *P < 0.05 vs. PBS in corpus, †P < 0.05 vs. PBS in antrum.