The nearby edge-on spiral galaxy NGC 4945 makes an excellent "laboratory" for studying the molecular content and dynamics of galaxies in general. It contains a heavily obscured starburst region with many detectable molecular lines, and also an AGN. We have used the ATCA to observe the 3-mm transitions of HCN, HCO+ and HNC to probe the chemistry and dynamics of the nucleus of this galaxy with arcsecond resolution. The results, which we present here, are consistent with the presence of a thick, edge-on circumnuclear molecular torus with a radially varying excitation gradient.