Lp estimates for the wave equation associated to the Grushin operator

We prove that the solution of the wave equation as- sociated to the Grushin operator $ G = -\Delta +|x|^2 \partial_t^2 $ is bounded on $ L^p(R^{n+1})(1 < p < \infty)$, when $|1/p- 1/2 | < 1/n+2$ .