Drug challenges reveal differences in mediation of stress facilitation of voluntary alcohol drinking and withdrawal-induced anxiety in alcohol-preferring P rats

Abstract

Background: There is controversy over whether exposure to stress precipitates relapse and/or increases alcohol (ethanol) intake. Our laboratory has demonstrated that repeated stress prior to withdrawal from a brief forced exposure to alcohol results in withdrawal-induced anxiety-like behavior. Because anxiety is often regarded as a precipitating factor in relapsing alcoholics, we decided to examine the consequences of stressing alcohol-preferring P rats on both voluntary alcohol drinking and withdrawal-induced anxiety.

Methods: P rats were subjected to 3 cycles of 5 days of voluntary alcohol drinking and 2 days of deprivation. Restraint stress (60 min) was applied to some animals during the first and second deprivations/withdrawals (at 4 h). Drugs (flumazenil, buspirone, SB242,084, CP154,526, CRA1000, naloxone, haloperidol, olanzapine, naloxone, and haloperidol) were given to some rats 30 min prior to restraint stress.

Results: Stressed, deprived P rats exhibited both a longer duration of elevated alcohol drinking and anxiety-like behavior in the social interaction test upon withdrawal after the third cycle of voluntary alcohol drinking. When given prior to each of the restraint stresses, the benzodiazepine receptor antagonist flumazenil (5 mg/kg), the corticotrophin releasing factor receptor antagonists CRA1000 (3 mg/kg) and CP154,526 (10 mg/kg), the serotonin 5-HT(1A) receptor partial agonist buspirone (0.6 mg/kg), and the mixed 5-HT(2C)/D2 receptor antagonist olanzapine were effective in reducing the increased duration of elevated alcohol drinking and the withdrawal-induced anxiety-like behavior. In contrast, while the opiate receptor antagonist naloxone (20 mg/kg), the 5-HT(2C) receptor antagonist SB242084 (3 mg/kg), and the dopamine receptor antagonist haloperidol (0.1 mg/kg) also reduced drinking, they did not significantly alter anxiety like behavior.

Conclusion: These results suggest that stress-induced facilitation of alcohol drinking and withdrawal-induced anxiety-like behavior in P rats may be closely but imperfectly linked.

Fig. 1

Research design for drug treatment and stress application in P rats repeatedly withdrawn from alcohol.

Fig. 2

Daily alcohol intake (g/kg/d) in P rats continuously exposed to alcohol, deprived of alcohol, or deprived and stressed. Average intake for the first 5 days is presented as Treatment Day 0. The data represent the means ± SEM for n = 8 animals in each of the 3 groups. There was a 2-day break between Days 0 and 1 and between Days 5 and 6 of postdeprivation alcohol exposure during which time the rats had water only. SI, social interaction.

Fig. 3

Social interaction behavior in alcohol-withdrawn P rats continuously exposed to alcohol, deprived twice from alcohol, or deprived and stressed twice. The test was carried out 5 h after the last alcohol session. Data represent the mean s ± SEM time spent in social interaction for 16 to 24 rats in the upper panel and line crosses in the lower panel. *Significantly different from the Continuous Alcohol Group.

Fig. 4

Cumulative alcohol intake of P rats after treatment with flumazenil, CRA1000, CP154,526, and buspirone. Drug-treated rats were injected 30 min before the application of 1 h of restraint stress during the first and second withdrawal/deprivation periods. Values represent the mean increase in cumulative alcohol intake between the first and third cycles for 7 to 10 rats. *Significantly different from Continuous Alcohol; +significantly different from Deprivation alone; #significantly different from Vehicle.

Fig. 5

Cumulative alcohol intake of P rats after treatment with naloxone, SB242084, haloperidol, and olanzapine. Drug-treated rats were injected 30 min before the application of 1 h of restraint stress during the first and second withdrawal/deprivation periods. Values represent the mean increase in cumulative alcohol intake between the first and third cycles for 7 to 10 rats. The bars for Continuous Alcohol, Deprivation only and Vehicle groups are repeated from Fig. 4. *Significantly different from Continuous Alcohol, +significantly different from Deprivation alone; #significantly different from Vehicle.

Fig. 6

Social interaction behavior in alcohol-withdrawn P rats after prior treatment with flumazenil, CRA1000, CP154,516, and buspirone. Drug-treated rats were injected 30 min before the application of 1 h of restraint stress during the first and second withdrawal/deprivation periods. Social interaction behavior was tested approximately 5 h after the removal of the alcohol tube at the end of the third cycle. Data represent the s + SEM for 7 to 10 rats. *Significantly different from Continuous Alcohol; #significantly different from Vehicle.

Fig. 7

Social interaction in alcohol-withdrawn P rats after prior treatment with naloxone, SB242084, haloperidol, or olanzapine. Drug-treated rats were injected 30 min before the application of 1 h of restraint stress during the first and second withdrawal/deprivation periods. Social interaction behavior was tested approximately 5 h after the removal of the alcohol tube at the end of the third cycle. Data represent the s + SEM for 7 to 8 rats. The first 3 bars are repeated from Fig. 6. *Significantly different from Continuous Alcohol; #significantly different from Vehicle.

Fig. 8

Effects of Flumazenil and CRA1000 on the daily pattern of drinking in stressed, alcohol deprived P rats. Rats were subjected to the protocol illustrated in Fig. 1, with flumazenil, and CRA1000 being injected 30 min prior to the application of stress. Animals with continuous access to alcohol and water were compared to: (1) those with cycled exposure to alcohol with two 2-day deprivation periods interspersed between three 5-day cycles of exposure to water and alcohol and (2) those with cycled exposure to alcohol with stress added during the deprivation periods with and without flumazenil or CRA1000.