An excitable activator-inhibitor system with relatively fast inhibitor
diffusion is considered. Numerical simulations of wave propagation in
side long channels show transitions from stable flat traveling waves t
o folded waves and further to spreading spiral turbulence as the inhib
itor diffusivity is increased. For sufficiently narrow channels the su
ppression of turbulence and the development of regular steadily propag
ating patterns is observed. The curvature dependence of the wave propa
gation velocity is derived and used to interpret the observed phenomen
a.