ON THE ELEVATED PLUS-MAZE THE ANXIOLYTIC-LIKE EFFECTS OF THE 5-HT1A AGONIST, 8-OH-DPAT, BUT NOT THE ANXIOGENIC-LIKE EFFECTS OF THE 5-HT1A PARTIAL AGONIST, BUSPIRONE, ARE BLOCKED BY THE 5-HT1A ANTAGONIST, WAY-100635

In the present study we evaluated the effects of the 5-HT1A receptor p artial agonist, buspirone hydrochloride and the 5-HT1A receptor agonis t, 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) on the elevated plus-maze. In addition, the ability of the 5-HT1A receptor antagonist , WAY 100635, to reverse the effects of both compounds was determined. 8-OH-DPAT (0.01-0.3 mg/kg, SC) dose-dependently increased the percent time on, and the number of entries to, the open arms of the maze. In a second experiment, WAY 100635 (0.003-0.3 mg/kg, SC) dose-dependently reversed the anxiolytic-like effects of 8-OH-DPAT (0.3 mg/kg, SC). In a third experiment, buspirone (0.3-4.0 mg/kg, SC) dose-dependently de creased the time spent on the open arms of the maze, indicating that i t had anxiogenic-like effects. Buspirone also significantly decreased locomotor activity, which was evident in the decreases in the distance travelled on the open arms. closed arms and on the maze as a whole, t he total number of arm entries and the mean speed of the animals. In c ontrast to its effects on 8-OH-DPAT-induced behaviours in the maze, WA Y 100635 (0.003-1.0 mg/kg SC) failed to reverse any of the effects ind uced by buspirone. Animals treated with high doses of WAY 100635 (0.3- 1.0 mg/kg SC) alone did not significantly differ from vehicle-treated animals on any of the measures recorded during elevated plus-maze tria ls. These data suggest that the anxiolytic-like effects of 8-OH-DPAT, but not the anxiogenic-like effects of buspirone, on the elevated plus -maze are mediated via S-HT1A receptors in the CNS.