  The interaction of the pseudoscalar meson and the baryon octet is
investigated by solving the Bethe-Salpeter equation in the unitary
coupled-channel approximation, In addition to the Weinberg-Tomozawa term, the
contribution of the $s-$ and $u-$ channel potentials in the S-wave
approximation are taken into account. In the sector of isospin $I=1/2$ and
strangeness $S=0$, a pole is detected in the reasonable region on the complex
energy plane of $\sqrt{s}$ in the center of mass frame by analyzing the
behavior of the scattering amplitude, which is higher than the $\eta N$
threshold and lies on the third Riemann sheet. Thus it can be regarded as a
resonance state and might correspond to the $N(1535)$ particle in the review of
the Particle Data Group(PDG). The coupling constants of this resonance state to
the $\pi N$, $\eta N$, $K \Lambda$ and $K \Sigma$ channels are calculated, and
it is found that this resonance state couples strongly to the hidden strange
channels. Apparently, the hidden strange channels play an important role in the
generation of the resonance state with strangeness zero. The interaction of the
pseudoscalar meson and the baryon octet is repulsive in the sector of isospin
$I=3/2$ and strangeness $S=0$, therefore, no resonance state can be generated
dynamically.
