  The s-wave meson-nucleon interaction in the S=-1 sector is studied by means
of a coupled-channel Lippmann Schwinger equation, using the lowest order chiral
Lagrangian and a cut off to regularize the loop integrals. The position and
width of the Lambda(1405) resonance and the K^- p scattering cross sections at
low energies are well reproduced. The inclusion of the eta Lambda, eta Sigma^0
channels in the coupled system is found very important and allows a solution in
terms of only the lowest order Lagrangian. The model is applied to calculate
the in-medium K^- self-energy to which we add a small p-wave piece resulting
from the coupling to hyperon particle-nucleon hole excitations. The K^- feels
an attraction of about -100 MeV at normal nuclear density. The Lambda(1405)
resonance shifts to energies above the $K^-p$ threshold and ends up dissolving
as density increases. It remains to be seen how these effects persist when the
dressing of the Kbar and the pi mesons is incorporated self-consistently in the
calculation.
