Male rats used in the biochemical and motor activity experiments were of the Sprague- Dawley strain (ALAB,Sollentuna, Sweden), weighing 200-300 g. U-92016A was administrated po (10 mkM/kg) or iv (4.0mkM/kg).

Male Sprague-Dawley rats (160-225 g) were killed by decapitation and the whole brain with the exception of the brain stem and cerebellum was rapidly removed, weighed, and chilled in ice cold 0.9% sodium chloride. Each brain was homogenized (Ultra-Turrax, 20 s) in 10 mL of ice cold 50 mM Tris buffer (pH 8.0 at 25 oC) containing 120 mM sodium chloride, 4 mM calcium chloride, and 4 mM magnesium chloride and centrifuged at 20000g at 4OC for 10 min. Pellets were resuspended in 10 mL of fresh buffer and preincubated for 10 min in a 37 OC water bath and then recentrifuged. Final pellets were homogenized in 100 volumes (w/v) of Tris buffer (as described above) containing 10 mkM pargyline. The incubation tubes were kept on ice in triplicates and received 100 pL of U-92016A solution in water (or water for total binding) and 1000 mkL of membrane suspension (corresponds to 10 mg of original tissue). The binding experiment was initiated by addition of 100 mkL of [3H]-8-OH-DPAT (specific activity 219-221 Ci/mmol) in ascorbic acid (the final incubation concentration was 1 nM [3H]-8-OH-DPAT in 0.1% ascorbic acid). After incubation for 15 min at 37 OC the reaction was terminated by separation of the free radioligand from bound by rapid vacuum filtration using a cell harvester equipment (Brandels 48 sample harvester). The tubes were rinsed with 4 mL, and the filters (Whatman GFB) were washed twice with 4 mL of ice cold 0.9% sodium chloride.