Plays a role in neuronal membrane excitation, important for normal response properties of the photoreceptor. Able to control excitability from either neurons or glia cells. Ine negatively regulates neuronal sodium channels. Controls neurotransmitter-mediated signaling pathways associated with the structure of the larval peripheral nerve, ine and eag control perineurial glial growth through partially redundant pathways. Isoform A and isoform B are both functional, although isoform A functions with greater efficiency. Has a role in osmolyte transport within the Malpighian tubule and hindgut. Expressed both maternally and zygotically. Developing embryos exhibit expression in the posterior hindgut, foregut, midgut, Malpighian tubules, anal plate, Garland cells, and a subset of cells in the central nervous system. Central nervous system expression is seen in segmentally repeating in cells flanking the midline of the ventral ganglion. Isoform A and isoform B are colocalized in both the nervous system and the fluid reabsorption system. Flies lacking this protein, in a wild-type background, display no observable behavioral defects. In a Shaker mutant background, flies lacking ine exhibit downturned wings and an indented thorax. Flies lacking ine exhibit increased excitability of the larval peripheral nerve by causing the defective re-uptake of the substrate neurotransmitter of the ine transporter and thus overstimulation by this neurotransmitter. Flies lacking ine increase the growth of the perineurial glial layer of the larval peripheral nerve. Flies overexpressing ine exhibit delayed onset of long-term facilitation and increased failure rate of transmitter release at the larval neuromuscular junction, reduced amplitude of larval nerve compound action potentials, suppression of the leg-shaking behavior of mutants defective in the Shaker-encoded potassium channel, and temperature-sensitive paralysis. The long N terminus is uncommon among members of the sodium- and chloride-dependent neurotransmitter transporter family but is required for efficient transporter activity. Belongs to the sodium:neurotransmitter symporter (SNF) (TC 2.A.22) family.