Pi subunit of the heteropentameric ligand-gated chloride channel gated by gamma-aminobutyric acid (GABA) (PubMed:10462548). GABA-gated chloride channels, also named GABA(A) receptors (GABAAR), consist of five subunits arranged around a central pore and contain GABA active binding site(s) located at the alpha and beta subunit interfaces (By similarity). When activated by GABA, GABAARs selectively allow the flow of chloride anions across the cell membrane down their electrochemical gradient (PubMed:10462548). Pi-containing GABAARs are mostly located in peripheral tissues. In the uterus, pi subunits modulate uterus contraction by altering the sensitivity of GABAARs to pregnanolone (PubMed:9182563). In the lungs, pi-containing GABAARs contribute to pulmonary fluid transport via luminal secretion of chloride (By similarity). {ECO:0000250|UniProtKB:O09028, ECO:0000250|UniProtKB:P47870, ECO:0000269|PubMed:10462548, ECO:0000269|PubMed:9182563}. This is the function of GABRP (gamma-aminobutyric acid type A receptor subunit pi, ENSG00000094755).