10 symmetrically ocular hypertensive patients were treated with a single drop of 1%, 2% and 5% corynanthine solution. The 1% solution showed no effect while the 2% solution reduced IOP for at least 8 hours and the 5% solution showed a significant reduction in IOP in both eyes.

The binding constants obtained for 26 compounds (including, corynanthine) were determined by the 3-curve approach. Of these compounds WB4101, corynanthine, rauwolscine, yohimbine, ARC 239 and prazosin were found to be clearly alpha2C-selective; their electivites ranging from 16 to 30 fold (Kd for corynanthine = 232 nM). Radioligand binding was performed in 150 uL of 1 mM EDTA, 100 uM Gpp(NH)p (guanyl-5'-yl-imido-diphos-phate), 140 mM NaCl, 33 mM Tris-Cl, pH 7.5 with [3H]-MK912 and drugs for 1 h at 25°C and then filtering and washing on Whatman GF/C filters.