The expression of calcitonin gene-related Peptide and acetylcholine in the vestibular-related nucleus population of wild-type mice and retinal degeneration fast mice after rotary stimulation.

Due to the lack of an appropriate animal model, few studies have addressed the integration of visual and vestibular information in the visual system. Using a mouse model with a visual defect (retinal degeneration fast, rdf), we have verified that the prepositus hypoglossal nucleus (PrH) and the Kooy cap of the inferior olive medial nucleus (IOK) are key regions in which visual and vestibular information integrate. Although the integration regions were identified, the precise mechanisms of integration require further investigation. The rdf mice and wild-type Kunming mice were randomly assigned to experimental and control subgroups, respectively. Mice in the experimental groups were exposed to rotary motion for 30 min three times at 24-h intervals, whereas mice in the control groups were not exposed to rotary motion. Differences in the number of calcitonin gene-related peptide positive (CGRP-positive) and choline acetyltransferase positive (ChAT-positive) neurons in the vestibular-related nucleus populations of two types of mice were determined. After rotatory stimulus, the number of CGRP-positive and ChAT-positive neurons in the PrH and the IOK was significantly less in rdf mice compared with that in wild-type mice. There were differences in the number of CGRP-positive and ChAT-positive neurons in the other vestibular-related regions, but the differences were not significant, except the difference in the number of ChAT-positive neurons in the medial vestibular nucleus. The expression patterns of CGRP and ChAT were similar to that of Fos in the vestibular-related regions in the two types of mice after rotatory stimulus. The number of CGRP-positive and ChAT-positive neurons and the number of active nerve cells were consistent in those regions in the two types of mice after rotary stimulus. Therefore, we speculated that CGRP and Ach generated and released by neurons in the PrH and the IOK may play roles in the sensory integration of visual and vestibular information in mice.

Expression of calcitonin gene-related peptide in efferent vestibular system and vestibular nucleus in rats with motion sickness.

UNLABELLED: Motion sickness presents a challenge due to its high incidence and unknown pathogenesis although it is a known fact that a functioning vestibular system is essential for the perception of motion sickness. Recent studies show that the efferent vestibular neurons contain calcitonin gene-related peptide (CGRP). It is a possibility that the CGRP immunoreactivity (CGRPi) fibers of the efferent vestibular system modulate primary afferent input into the central nervous system; thus, making it likely that CGRP plays a key role in motion sickness. To elucidate the relationship between motion sickness and CGRP, the effects of CGRP on the vestibular efferent nucleus and the vestibular nucleus were investigated in rats with motion sickness. METHODS: An animal model of motion sickness was created by subjecting rats to rotary stimulation for 30 minutes via a trapezoidal stimulation pattern. The number of CGRPi neurons in the vestibular efferent nucleus at the level of the facial nerve genu and the expression level of CGRPi in the vestibular nucleus of rats were measured. Using the ABC method of immunohistochemistry technique, measurements were taken before and after rotary stimulation. The effects of anisodamine on the expression of CGRP in the vestibular efferent nucleus and the vestibular nucleus of rats with motion sickness were also investigated. RESULTS AND DISCUSSION: Both the number of CGRPi neurons in the vestibular efferent nucleus and expression level in the vestibular nucleus increased significantly in rats with motion sickness compared to that of controls. The increase of CGRP expression in rats subjected to rotary stimulation 3 times was greater than those having only one-time stimulation. Administration of anisodamine decreased the expression of CGRP within the vestibular efferent nucleus and the vestibular nucleus in rats subjected to rotary stimulation. In conclusion, CGRP possibly plays a role in motion sickness and its mechanism merits further investigation.