Integration of Vestibular and Gastrointestinal Inputs by CerebellarFastigial Nucleus Neurons: Multisensory Influences on MotionSickness

摘要

Previous studies demonstrated that ingestion of the emetic compound copper sulfate (CuSO4) alters the responses to vestibular stimulation of a large fraction of neurons in brainstem regions that mediate nausea and vomiting, thereby affecting motion sickness susceptibility. Other studies suggested that the processing of vestibular inputs by cerebellar neurons plays a critical role in generating motion sickness, and that neurons in the cerebellar fastigial nucleus receive visceral inputs. These findings raised the hypothesis that stimulation of gastrointestinal receptors by a nauseogenic compound affects the processing of labyrinthine signals by fastigial nucleus neurons. We tested this hypothesis in decerebrate cats by determining the effects of intragastric injection of CuSO4 on the responses of rostral fastigial nucleus to whole-body rotations that activate labyrinthine receptors. Responses to vestibular stimulation of fastigial nucleus neurons were more complex in decerebrate cats than reported previously in conscious felines. In particular, spatiotemporal convergence (STC) responses, which reflect the convergence of vestibular inputs with different spatial and temporal properties, were more common in decerebrate than in conscious felines. The firing rate of a smallpercentage of fastigial nucleus neurons (15%) was altered over50% by the administration of CuSO4; the firing rate of themajority of these cells decreased. The responses to vestibular stimulation of amajority of these cells were attenuated after the compound was provided.Although these data support our hypothesis, the low fraction of fastigialnucleus neurons whose firing rate and responses to vestibular stimulation wereaffected by the administration of CuSO4 cast doubt on the notion thatnauseogenic visceral inputs modulate motion sickness susceptibility principallythrough neural pathways that include the cerebellar fastigial nucleus. Instead,it appears that convergence of gastrointestinal and vestibular inputs occursmainly in the brainstem.