The effect of raphe lesion on sleep in the rat

The midbrain raphe nuclei (nucleus raphe dorsalis and nucleus raphe medialis) were destroyed by electrocoaggulation in rats. On the first few days following the lesion, a marked hyperactivity was observed in lesioned animals as well as in shame-operated controls. Between the 5th and 36th days after the lesion, sleep patterns did not differ either qualitatively or quantitatively from the shame-operated and intact controls. The forebrain 5-HT level was reduced to 33.85%. It is concluded, that in rats restoration of the sleep system after the destruction of midbrain raphe nuclei is extremely rapid and effective. 5-HT seems to play an important role in this restored sleep system even though the forebrain 5-HT content was still markedly reduced.