beta-Carboline and pentylenetetrazol effects on conflict behavior in the rat

The beta-carbolines and the convulsant agent pentylenetetrazol (PTZ) have been reported as "anxiogenic" in several animal models for anxiety. The present study examined the effects of the beta-carboline noreleagnine (NOR) and PTZ, administered alone and in combination with the benzodiazepine antagonist, Ro 15-1788, on behavior in the conditioned suppression of drinking (CSD) conflict procedure. In daily 10-min sessions, water-deprived female SD rats were trained to drink from a tube that was electrified (0.25 mA). Electrification was signaled by a tone. Acute (20-min) treatment with NOR or PTZ resulted in a dose-dependent decrease in both punished responding (shocks received) and unpunished responding (water intake). Both NOR and PTZ decreased punished responding only at doses that also depressed unpunished responding. Coadministration of Ro 15-1788 (2 mg/kg) reduced the effects of NOR on punished, but not unpunished, responding; this Ro 15-1788 cotreatment reduced the effects of PTZ on both punished and unpunished responding. These data suggest that both PTZ and NOR produce benzodiazepine receptor-mediated anxiogenic-like effects on conflict behavior.