GABA receptor that functions as an excitatory cation channel. Permeable to monovalent cations such as Na(+) and K(+) (PubMed:14555952). Has negligible divalent cation permeability (PubMed:14555952). Does not act as a chloride channel (PubMed:14555952). Mediates enteric muscle contractions required for defecation (PubMed:14555952, PubMed:2323555, PubMed:16236771). Probably by regulating the defecation motor program, required for fatty acid uptake by intestinal cells (PubMed:25849533). Interacts with tax-6; tax-6 may be involved in negative regulation of exp-1 activity. May self-associate to form homodimer. Expressed in the intestinal and anal depressor muscles but not in the sphincter muscle. Also detected in the RID and SABD ring interneurons, the ADE sensory neuron and the PDA motor neuron. Defective in enteric muscle contraction resulting in abnormal defecation cycles and moderate to severe constipation. Resistant to channel blocking activity of mecamylamine and bicuculline. Belongs to the ligand-gated ion channel (TC 1.A.9) family. Gamma-aminobutyric acid receptor (TC 1.A.9.5) subfamily.