Evidence for an anti-amnesic effect of JO 1784 in the rat: a potent and selective ligand for the sigma receptor.

JO 1784 ((+)-N-Cyclopropyl-methyl-N-methyl-1,4-diphenyl-1-yl-but-3-en-1-ylami ne, hydrochloride), has been recently described as a selective ligand for the sigma receptor with an IC50 of 39 +/- 8 nM28. In the present study the effects of JO 1784 on experimental induced amnesia were investigated using one trial passive avoidance task in rats. Amnesia was produced by injecting scopolamine (1 mg/kg i.p.) 30 min before the second session (T2) on day 2 of the passive avoidance task. The anti-amnesic effect of JO 1784 was compared with other typical and atypical psychotropic drugs which interact at the sigma and or the phencyclidine site. JO 1784 was studied at 5 doses; 0.0625, 0.25, 1.0, 4.0 and 16.0 mg/kg i.p. ((+)-3-(3-hydroxyphenyl)-N-1-(propyl)piperidine ((+)-3-PPP). Rimcazole, (+)-N-allylnormetazocine ((+)-NANM), 1,3-di(2-tolyl) guanidine (DTG) were studied at 4 doses; 0.25, 1.0, 4.0 and 8.0 mg/kg i.p. All drugs were administered 60 min before the test (T2) on day 2 i.e. 30 min before scopolamine. Piracetam (1000 mg/kg p.o.) administered in the same test conditions was used as a reference compound in each experiment. Of the drugs investigated JO 1784 (0.25, 1.0, 4.0 and 16.0 mg/kg i.p.), (+)-3-PPP (0.25, 1.0 and 4.0 mg/kg i.p.), DTG (1.0, 4.0 and 8.0 mg/kg) and piracetam significantly reversed scopolamine induced amnesia on day 3 (T3). At the lower dose, JO 1784 (0.0625 mg/kg) failed to reverse the amnesic effects of scopolamine on day 3. These results suggest that JO 1784 the selective sigma ligand, may be beneficial in amnesic status.