[Hypersomnia by isthmic lesion in cat. Study of the metabolism of cerebral monamines].

(1) A significant increase of 5-HT synthesis is observed in several areas of the cat brain 24 h after the bilateral destruction of the dorsal noradrenergic bundle in the isthmus. This stimulation of the synthesis was simultaneously observed at the level fo serotoninergic cell bodies (anterior part of the raphe system) and of 5-HT terminals (cortex, thalamus, mesencephalon, medulla oblongata). Conversely, a significant decrease of 5-HT synthesis was found in the caudal part of the raphe and in the hypothalamus. The possibility of a catecholaminergic control of 5-HT synthesis by neurons passing through the isthmus is discussed. (2) in the same experimental conditions, an important decrease of endogenous dopamine content without any subsequent change of noradrenaline concentration was observed in the thalamus, the geniculate body and the pons. This important decrease could be due to a greater utilization of dopamine into hypothetical dopaminergic terminals localized in these structures.