Infusion of flesinoxan into the amygdala blocks the fear-potentiated startle.

In a previous study it was demonstrated that flesinoxan, a selective serotonin (5-HT)1A receptor agonist, had anxiolytic properties in the fear-potentiated startle paradigm. The present study investigated the putative site of action of flesinoxan in this paradigm. Flesinoxan infused either into the dorsal raphe nucleus or the median raphe nucleus did not affect startle potentiation.

The anxiolytic effect on the fear-potentiated startle is not due to a non-specific disruption.

In the present study, the effects of alprazolam, chlordiazepoxide, ethanol and haloperidol in the strychnine-potentiated startle response paradigm were investigated. Because strychnine increases control startle levels without fear-conditioning, no central state of fear exists. When anxiolytic drugs reduce the fear-induced potentiation of the startle response without reducing the strychnine-induced startle potentiation, their attenuating effect on startle potentiation in the fear-potentiated startle response paradigm can more likely be attributed to their anxiolytic properties.

The effects of 5-HT1A receptor agonists, 5-HT1A receptor antagonists and their interaction on the fear-potentiated startle response.

The present study investigated whether the anxiolytic effect of 5-HT1A receptor agonists on the fear-potentiated startle response could be antagonized by 5-HT1A receptor antagonists. Therefore, control and fear-potentiated startle amplitudes were measured after co-administration of vehicle, flesinoxan (10 mg/kg PO) or 8-OH-DPAT (0.3 mg/kg SC) and DU 125,530 (0, 1, 3 and 10 mg/kg SC), (+/-)-pindolol (0, 3, 10 and 30 mg/kg SC) or WAY 100,635 (0, 0.

Effects of 5-HT1A receptor ligands in a modified Geller-Seifter conflict model in the rat.

In a modified Geller-Seifter conflict procedure, rats were trained to lever-press for food under a multiple variable interval-fixed ratio (VI30: food; FR10: food + shock) schedule of reinforcement. The ability to antagonize response suppression in the punished period is considered a good predictor for anxiolytic activity. Chlordiazepoxide and alprazolam increased punished responding.

Control conditions in the fear-potentiated startle response paradigm.

In the present study, the fear-potentiated startle response paradigm was modified in order to investigate the decrease in control startle levels often observed after administration of anxiolytic drugs. The within-animal comparison of control startle amplitudes and fear-potentiated startle amplitudes normally used was replaced by a between-animal comparison. Moreover, the experimental design was extended with an additional control group, a no-shock group.