Secondary vestibular cholinergic projection to the cerebellum of rabbit and rat as revealed by choline acetyltransferase immunohistochemistry, retrograde and orthograde tracers

Abstract

Previously we have shown that four regions of the cerebellum, the uvula-nodulus, flocculus, ventral paraflocculus, and anterior lobe 1, receive extensive, but not exclusive, cholinergic mossy fiber projections. In the present experiment we have studied the origin of three of these projections in the rat and rabbit (uvula-nodulus, flocculus, ventral paraflocculus), using choline acetyltransferase (ChAT) immunohistochemistry in combination with a double label, retrogradely transported horseradish peroxidase (HRP). We have demonstrated that in both the rat and rabbit the caudal medial vestibular nucleus (MVN) and to a lesser extent the nucleus prepositus hypoglossus (NPH) contain ChAT-positive neurons. Neurons of the caudal MVN are double-labeled following HRP injections into the uvula-nodulus. HRP injections into the uvula-nodulus also labeled less than 5% of the neurons in the cholinergic vestibular efferent complex. Fewer ChAT-positive neurons in the MVN and some ChAT-positive neurons in the NPH are double-labeled following HRP injections into the flocculus. Almost no ChAT-positive neurons in the MVN and some ChAT-positive neurons in the NPH are double-labeled following HRP injections into the ventral paraflocculus. Injections of Phaseolus leucoagglutinin (PHA-L) into the caudal MVN of both the rat and rabbit demonstrated projection patterns to the uvula-nodulus and flocculus that were qualitatively similar to those observed using ChAT immunohistochemistry. We conclude that the cholinergic mossy fiber pathway to the cerebellum in general and the uvula-nodulus in particular is likely to mediate secondary vestibular information related to postural adjustments.

Responses of caudal vestibular nucleus neurons of conscious cats to rotations in vertical planes, before and after a bilateral vestibular neurectomy

“…The CVN have functions in addition to autonomic regulation, as this region projects to the cerebellar nodulus and uvula (Epema et al 1985;Sato et al 1989;Thunnissen et al 1989;Barmack et al 1992) as well as to the dorsal horn of the upper cervical spinal cord (Peterson et al 1978;Bankoul et al 1995). The present data indicate that these areas mainly receive from the CVN relatively simple signals regarding head position or head velocity, at least during rotations in vertical planes.…”

“…For example, a specialized projection to the upper cervical spinal cord arises from the CVN (Peterson et al 1978); this projection differs from the classical vestibulospinal tracts in that it terminates mainly in the dorsal horn (Bankoul et al 1995), and is presumably involved in modulating the processing of sensory signals from neck receptors. The CVN also provide considerable inputs to the cerebellar nodulus and uvula (Epema et al 1985;Sato et al 1989;Thunnissen et al 1989;Barmack et al 1992). Furthermore, the CVN project to medullary regions that participate in regulation of blood pressure and breathing (Balaban and Beryozkin 1994;Yates et al 1995;Ruggiero et al 1996;Porter and Balaban 1997;Martinelli et al 2007), and lesions of the CVN abolish cardiovascular and respiratory responses to stimulation of vestibular afferents (Uchino et al 1970;Yates et al 1993;Kerman and Yates 1998).…”

Brainstem projections to molecular layer heterotopia of the cerebellar vermis: Evidence from the Allen Mouse Brain Connectivity Database

“…Previously, we also demonstrated that axons expressing choline acetyl-transferase (ChAT) are found in heterotopia using immunocytochemistry [5]. In the present report GFP-labeled axons were present in heterotopia after injection into the NPP which is known to contain ChAT-expressing neurons with cerebellar projections [27]. These data confirm the presence of cholinergic axons in heterotopia and now reveal the source of these afferent which include the NPP.…”

Immunoreactivity for calcium-binding proteins defines subregions of the vestibular nuclear complex of the cat

“…Barmack described many ChAT-immunoreactive cells dorsally in the VNC of the rabbit (Barmack et al 1992b(Barmack et al , 1992c. The location of these cells appears to overlap the calretinin area, raising the possibility that some of the calretinin-immunoreactive cells might be cholinergic.…”