- theta, a novel gamma-aminobutyric acid type A receptor subunit. Bonnert, T.P., McKernan, R.M., Farrar, S., le Bourdellès, B., Heavens, R.P., Smith, D.W., Hewson, L., Rigby, M.R., Sirinathsinghji, D.J., Brown, N., Wafford, K.A., Whiting, P.J. Proc. Natl. Acad. Sci. U.S.A. (1999)