Afferents to the cerebellar lateral nucleus. Evidence from retrograde transport of horseradish peroxidase after pressure injections through micropipettes

Abstract

HRP was injected by pressure from glass capillary micropipettes unilaterally into the lateral nucleus of rat so as to encompass the entire nucleus, but without spread into the interpositus nuclei. The cells of origin of the afferents to the lateral nucleus were studied after retrograde transport of the HRP. The reticulotegmental nucleus of the pons was labelled bilaterally and is the major source of crossed and uncrossed reticular imputs. The pontine nuclei also provide extensive crossed and uncrossed afferents. The inferior olive gives a large crossed olivo-lateral nucleus projection and a minor uncrossed input. The trigeminal nuclear complex--the nucleus of the spinal tract and the mesencephalic, principal sensory, and motor nuclei--all provide uncrossed afferents. The rostral portion of the lateral reticular nucleus gives a small crossed and uncrossed projection while the perihypoglossal nuclei and the dorsal parabrachial body give crossed afferents to the lateral nucleus. The norepinephrine afferent system from the locus coeruleus is represented by one or two heavily labelled cells and the serotonin raphe systems come from at least five raphe subgroups, the dorsal, superior centralis, pontis, obscurus and magnus nuclei. No evidence was found for commissural fibers between ipsilateral or contralateral cerebellar nuclei, or afferent axons from the spinocerebellar nuclei and the paramedian retricular nucleus. The significance of these sources of afferent imputs to the lateral cerebellar nucleus is discussed. The question is raised of the direct relationship between size of terminal axonal arborization and the quantity of HRP granules present in a cell retrograde transport. The limitations of the HRP method for detecting subtle local differences in the distribution of afferents within the heterogeneous groups of neurons in the lateral nucleus are discussed.

The effects of reversible inactivation of the red nucleus on learning-related and auditory-evoked unit activity in the pontine nuclei of classically conditioned rabbits.

“…Lesions of the dorsolateral pons, the caudal lateral pons, and the lateral lemniscus abolish conditioned responses to a toneconditioned stimulus (Steinmetz et al 1987). Anatomical and physiological data substantiate a direct and reciprocal connection between the IP nucleus and the dorsolateral and lateral pontine nuclei (Eller and Chan-Palay 1976;Watt and Mihailoff 1983;Gerrits and Voogd 1987;Steinmetz et al 1987;Steinmetz and Segelaub 1992;Gould et al 1993; J.K. Thompson, w.J. Spangler, and R.F.…”

Secondary trigeminocerebellar projections in sheep studied with the horseradish peroxidase tracing method

“…Finally, it is interesting to note that while trigeminocerebellar cortical fibers were found in the present study to be bilateral with a n ipsilateral preponderance, the HRP studies of Eller and Chan-Palay (1976) and Chan-Palay (1977) have shown that fibers from the PV and the Sp.V to the dentate (lateral) nucleus are ipsilateral in rat and bilateral in monkey and those from the Mes.V and the MV are ipsilatera1 in rat and contralateral in monkey.…”

Cerebellum and Cerebellar Connections

“…Studies on the organization of this collateralization using retrograde tracer injections in the cerebellar nuclei are hampered by the proximity of the afferent ongoing mossy fiber tracts to the cortex which may easily lead to false positive results. Therefore, retrograde experiments (Eller and Chan-Palay, 1976) required confirmation with anterograde tracer injections in the area of origin. Subsequently, the pontine nuclei and the nucleus reticularis tegmenti pontis (Gerrits and Voogd, 1987;Shinoda et al, 1992;Mihailoff, 1993a), the lateral reticular nucleus Wu et al, 1999), the spinal cord (Matsushita, 1999b;Matsushita and Xiong, 2001), and the raphe nucleus (Chan- Palay, 1977) have been confirmed with anterograde axonal tracing methods.…”