  The possible neutral $D^{(*)}\bar{D}^{(*)}$ and $B^{(*)}\bar{B}^{(*)}$
molecular states are studied in the framework of the constituent quark models,
which is extended by including the $s$-channel one gluon exchange. Using
different types of quark-quark potentials, we solve the four-body
Schr\"{o}dinger equation by means of the Gaussian expansion method. The bound
states of $D^{(*)}\bar{D}^{(*)}$ with $J^{PC}=1^{++},2^{++}$ and
$B^{(*)}\bar{B}^{(*)}$ with $J^{PC}=0^{++},1^{+-},1^{++},2^{++}$ are obtained.
The molecular states $D^{*}\bar{D}$ with $J^{PC}=1^{++}$ and $B^{*}\bar{B}$
with $J^{PC}=1^{+-}$ are good candidates for the $X(3872)$ and $Z^0_b(10610)$,
respectively.
