Dopaminergic involvement in the process of reinforcement from diethyl ether vapor in rats

1. Male and female Wistar rats were placed in boxes for 30 min daily and allowed to nose-poke in two holes on opposite walls, which opened into evaporation chambers through valves. One chamber contained diethyl ether vapor another-air, the contents being alternated randomly. 2. Rats inhaled the contents of evaporation chambers while nose-poking differed by the level of intake of diethyl ether vapor. Rats with the intake time of more than 3 sec formed about 15% of population. Their preference for diethyl ether was above 0.55. 3. There was significant negative correlation between the time of vapor inhalation and the time of immobility in forced swimming test in females but not in males. 4. Withdrawal of diethyl ether vapor decreased the inhalation time. On the first day after ether deprivation inhalation time rose above average level. Relationship between concentration of ether vapor and the time of its inhalation was inverted U-shaped function. Substitution of acetone vapor elevated the time of the vapor inhalation. 5. D-amphetamine in dose 0.05 mg/kg elevated the time of inhalation of and preference for ether vapor in some rats. In doses 0.05-1.0 mg/kg amphetamine selectively suppressed the time of vapor inhalation. 6. Haloperidol in doses 0.05 and 0.1 mg/kg elevated the time of vapor inhalation on the first day in females and suppressed it in doses 0.05-0.3 mg/kg dose-dependently on the second day. Atypical neuroleptic cis-carbidine elevated the time of vapor inhalation in doses 2.5 and 5.0 mg/kg and suppressed it at 10 mg/kg. 7. Diethyl ether vapor can be established as reinforcer in rats. Female rats are more liable to reinforcement from ether vapor than males and show more pronounced response to haloperidol. This may be related to its more active behavior in the forced swimming situation. 8. The results point to potential involvement of dopamine system in the process of reinforcement from ether vapor.