The interaction of polychromatic radiation of a dye laser with a neon gas-discharge plasma in shielded cylindrical tubes at medium gas pressures (1-30 Torr) near atomic spectral absorption lines of NeI atoms with wavelengths 650.6 and 656.2 nm was experimentally studied. Along the direction of propagation of the laser radiation, a shift in the central frequency of absorption is observed in the presence of inhomogeneities in the plasma column. The character of the optical transmission spectrum near narrow resonances was empirically shown to substantially depend on the density of absorbing atoms in a plasma; if this density exceeds 1012 cm-3, the contour of the transmission spectrum near the absorption resonance acquires a dispersive form. The general laws of the formation of nonstationary plasma transmission spectra depending on the laser power, the density of absorbing atoms, the nature of plasma inhomogeneities along the direction of propagation of laser radiation are examined in detail. The role of nonlinear and coherent effects and phase self-modulation during resonant interaction of short pulses of polychromatic laser radiation with gas-discharge plasma in narrow shielded tubes is discussed.