Behavioral effects of "vehicle" microinjected into the dorsal periaqueductal grey of rats tested in the elevated plus maze

To investigate the behavioral effects of different vehicles microinjected into the dorsal periaqueductal grey (DPAG) of male Wistar rats, weighing 200-250 g, tested in the elevated plus maze, animals were implanted with cannulas aimed at this structure. One week after surgery the animals received microinjections into the DPAG of 0.9 per cent (w/v) saline, 10 per cent (v/v) dimethyl sulfoxide (DMSO), 2 per cent (v/v) Tween-80, 10 per cent (v/v) propylene glycol, or synthetic cerebrospinal fluid (CSF). Ten min after the injection (0.5 mul) the animals (N = 8-13/group) were submitted to the elevated plus maze test. DMSO significantly increased the number of entries into both the open and enclosed arms when compared to 0.9 per cent saline (2.7 ñ 0.8 and 8.7 ñ 1.3 vs 0.8 ñ 0.3 and 5.1 ñ 0.9, respectively, Duncan test, P<0.05), and tended to increase enclosed arm entries as compared to 2 per cent Tween-80 (8.7 ñ 1.3 vs 5.7 ñ 0.9, Duncan test, P