Antagonism of inhibitory amino acids by the steroid derivative RU5135

Abstract
1 The steroid derivative RU5135 has been tested for its ability to antagonize glycine and the γ-aminobutyric acid (GABA) analogue muscimol on isolated preparations of rat optic nerve and cuneate nucleus, respectively. 2 On the cuneate nucleus, RU5135 antagonized muscimol in a competitive manner with a pA2 value of 8.31. RU5135 shared a common site of action with bicuculline that was separate from the Picrotoxin site. 3 On the optic nerve, RU5135 antagonized glycine with a pA2 of 7.67. It shared a common site of action with strychnine.