Effects of dihydrogenated ergot alkaloids on the sleep-wakefulness cycle and on brain biogenic amines in the rat.

Investigations with four dihydrogenated ergot alkaloids, dihydroergotoxine, dihydroergonine, dihydroergostine and dihydro-beta-ergosine indicate that they exert similar dose dependent effects on the sleep-wakefulness cycle of the rat. The duration of wakefulness was increased, non-rapid eye movement (NREM) and, in particular, rapid eye movement (REM) sleep were shortened. 5-Hydroxytryptophan, but not apomorphine, induced similar changes of the rat sleep-wakefulness cycle. Neurochemical studies on rat brain biogenic amines indicate that dihydroergotoxine lowers homovanillic acid (HVA) levels and reduces HVA elevations after morphine or haloperidol in the striatum. In addition, the turnover of serotonin was slowed down and 5-hydroxyindoleacetic acid (5-HIAA) content in the whole brain was reduced. 5-HIAA elevation induced by clozapine was inhibited. These results suggest that the electroencephalographic changes in the rat produced by treatment with dihydrogenated ergot alkaloids reflect an enhanced level of vigilance and could be related to changes of brain biogenic amine metabolism.