  The flux of very high-energy neutrinos produced in our Galaxy by the
interaction of accelerated cosmic rays with the interstellar medium is not yet
determined. The characterization of this flux will shed light on Galactic
accelerator features, gas distribution morphology and Galactic cosmic ray
transport. The central Galactic plane can be the site of an enhanced neutrino
production, thus leading to anisotropies in the extraterrestrial neutrino
signal as measured by the IceCube Collaboration. The ANTARES neutrino
telescope, located in the Mediterranean Sea, offers a favourable view on this
part of the sky, thereby allowing for a contribution to the determination of
this flux. The expected diffuse Galactic neutrino emission can be obtained
linking a model of generation and propagation of cosmic rays with the
morphology of the gas distribution in the Milky Way. In this paper, the
so-called "Gamma model" introduced recently to explain the high-energy gamma
ray diffuse Galactic emission, is assumed as reference. The neutrino flux
predicted by the "Gamma model" depends of the assumed primary cosmic ray
spectrum cut-off. Considering a radially-dependent diffusion coefficient, this
proposed scenario is able to account for the local cosmic ray measurements, as
well as for the Galactic gamma ray observations. Nine years of ANTARES data are
used in this work to search for a possible Galactic contribution according to
this scenario. All flavour neutrino interactions are considered. No excess of
events is observed and an upper limit is set on the neutrino flux of $1.1$
($1.2$) times the prediction of the "Gamma model" assuming the primary cosmic
ray spectrum cut-off at 5 (50) PeV. This limit excludes the diffuse Galactic
neutrino emission as the major cause of the "spectral anomaly" between the two
hemispheres measured by IceCube.
