Complicated potential structure formed at a constriction of positive column of a DC discharge with heated cathode in He at low discharge currents is investigated. According to the potential structure, electrons and ions are accelerated by the electric field and their energy distribution functions acquire multi humped shapes. Additional maximums on distribution functions quickly disappear due to collisions and radial losses. The nature of current passing through the Potential Structure (PS) is cleared up on the base of measured distributions. Attempt was made to calculate potential drop in DL taking into account electron energy distribution variations.