Mechanisms regulating the activity of facial nucleus motoneurons--IV. Influences from the brainstem structures.

Peculiarities of synaptic processes of facial motoneurons evoked by stimulation of brainstem structures were studied in acute experiments on anaesthetized and immobilized cats by intracellular recording technique. It was shown that stimulation of nucleus reticularis parvocellularis of the medulla oblongata as well as interstitial nucleus of Cajal, nucleus Darkschewitsch, periaqueductal gray and pretectal area evokes in facial motoneurons monosynaptic excitatory postsynaptic potentials accompanied by single action potentials. Somatic localization of synapses under study is supposed. Convergence of inputs is revealed. Functional role of the midbrain structures as intermediate relays transmitting descending signals to the facial nucleus is discussed.