The long-term effects of diazepam, lorazepam, and buspirone on behavioral suppression by a shock signal

The effects of anxiolytic drugs on novelty-induced place preference

Previous evidence has shown that rats exposed to a place preference apparatus prefer the novel compartment over the familiar. While this suggests that novelty is rewarding, an alternative interpretation is that rats avoid the familiar compartment because it is associated with some stress-related aversive event induced during the inescapable exposure sessions. To test this latter possibility, the benzodiazepine anxiolytic diazepam (0.1, 0.3, 1.0, 3.0 mg/kg) and the nonbenzodiazepine anxiolytic gepirone (0.1, 0.3, 1.0 mg/kg) were examined for their ability to alter novelty-induced place preference in rats. As expected, control animals showed a novelty-induced place preference. On the test day, this preference was disrupted by diazepam, but only at a dose (3 mg/kg) that also decreased locomotor activity. Gepirone failed to alter the preference behavior, even at a dose (1 mg/kg) that decreased locomotor behavior. In another experiment, rats spent more time in a familiar compartment that contained a novel object than in a familiar compartment with no object. These experiments indicate that preference for the novel compartment may reflect the rewarding effect of novelty rather than aversion to the familiar.

Discontinuation of diazepam and sensitivity to a shock signal: fear conditioning prior to drug treatment

The present experiment examined the disruptive capacity of a shock CS when Pavlovian training was completed prior to repeated daily treatment with diazepam (DZ). Two groups of rats were given 20 Pavlovian fear conditioning trials (two per day) to establish a light CS as a shock signal. Both groups were then trained for 15 daily sessions to bar press for food reinforcement. Before each session, one group was injected IP with 5 mg/kg DZ and the other with saline. All injections were discontinued after the last training session. Nine days later, the capacity of the CS to disrupt bar pressing was tested. The CS produced greater disruption of bar pressing for rats that had previously received chronic diazepam treatment. The results suggest that DZ discontinuation increases sensitivity to cues established as fear elicitors prior to initial administration of DZ.