Chemical lesions of both dorsal and median raphe nuclei and changes in social and aggressive behaviour in rats.

Microinjections of 5,7-dihydroxytryptamine into both the dorsal and median raphe nuclei resulted in 90% depletions of striatal and hippocampal 5-HT concentrations. Compared with vehicle-injected controls the lesioned rats showed reduced active social interaction scores in all four of the test conditions and also reduced levels of locomotor activity. The lesioned rats did not differ from the controls in their latency to start drinking in a novel environment; or in their response to intruder rats placed in their home cages, or in their behaviour as intruders when they were placed in the home-cages of unoperated rats. The difficulties of interpreting the behavioural effects of a lesion when the lesion produces hypoactivity, and the differences between the effects of these joint lesions of both dorsal and median raphe nuclei amd the effects of separate lesions of each nucleus are discussed.