Abstract
When rats are dropped from the supine position, the animals rotate their body in the air, and land on their feet (the air righting reflex). Vestibular input is thought to play crucial roles for elicitation of the air righting reflex. Nevertheless precise mechanisms inducing the reflex were unknown. To understand of functional roles of vestibular afferent input in eliciting the air righting reflex, we examined effects of vestibular lesions and stimulation on air righting movements. Furthermore, affected air righting movements were examined in detail by myographic activities. Lesions and stimulation were applied to vestibular nerves, and the lateral vestibular nuclei in Wistar male rats, in which electrodes for lesion and stimulation were implanted. Electromyographic activities were recorded from bilateral back muscles at the neck and lumbar. Unilateral lesions of the lateral vestibular nucleus elicited air righting movements with body rotation in too much extent (overshooting); in some cases repetitive rotation was observed. In such animals stimulation of the lateral vestibular nucleus of the intact side modified righting movements. In some cases, rotatory movements of the righting was facilitated, but in others they were weakened. The air righting movements with repetitive rotation was characterized by rhythmic bursts of back muscles, of which interburst intervals corresponded to the body rotation. It was suggested that vestibular input and the lateral vestibular nucleus could play important roles with complicated manners. [Jpn J Physiol 55 Suppl:S176 (2005)]
