[Reticular structures of the cat brain participating in startle reflexes in response to somatic stimuli of different modalities]

Abstract

Characteristics and reticular mechanisms of two types of late reflex responses (equivalents of the startle reflex) evoked by weak (tactile stimuli) and strong (high-threshold peripheral nerve stimulation) stimulations were studied in chloralose-anesthetized cats; these responses were designated as "tactile" (T) and "spino-bulbo-spinal" (SBS) reflexes, respectively. Some differences in the peripheral and central (brainstem) organization of these reflexes were found. In particular, the existence of the rostro-caudal differentiation of reticular structures involved in these types of reflexes was revealed using differential lesions of the brainstem reticular formation as well as its pharmacologic blockades (by means of microinjections of sodium chloride or procaine); the T-reflex was found to relay mainly through the pontine RF level, while the SBS-reflex--predominantly through the bulbar RF. Possible functional significance of the revealed differentiation in organization of some motor and sensory functions of the brainstem are discussed.