Ethanol prevents desensitization of 5-HT2 receptor-mediated responses consequent to defeat in territorial aggression.

Abstract

The effect of intruder status in territorial aggression on behavior in the elevated plus-maze, the open field and on 5-HT2 receptor-mediated behaviors was evaluated in male Long-Evans hooded rats. Intruders (350 g) were placed in the home cages of aggressive resident rats (475-600 g) and removed after 20 roll-tumble fights. On the following day, the rats were tested on the elevated plus-maze, and behavior in the open field was evaluated after injection with the 5-HT2/1C receptor agonist, DOI (1.0 mg/kg). The number of headshakes following DOI injection are thought to be an indicator of 5-HT2 receptor function. Although several other stressors were evaluated, only defeat in territorial aggression caused a significant decrement in the number of headshakes following DOI injection. To determine if ethanol (ET) could decrease the behavioral consequences of defeat, the effect of ET (1.25 g/kg) given before and immediately after aggression on behavior 24 hours later was evaluated. Although ET treatment had no effect on the control group that did not experience aggression, the ET treatment attenuated the desensitization of 5-HT2 receptor-mediated responses induced by aggression and severely exacerbated the anxiety-like effects as measured in the elevated plus-maze. These data suggest that (1) 5-HT2 receptor sensitivity decreases as a consequence of defeat, but not after several other stressors; (2) defeat in territorial aggression results in significant anxiety-like effects in the elevated plus-maze 24 hours later; and (3) these anxiety-like effects are exacerbated when ET is given before, and immediately after, the aggression.(ABSTRACT TRUNCATED AT 250 WORDS)