Projection from the cerebellar lateral nucleus to precerebellar nuclei in the mossy fiber pathway is glutamatergic: A study combining anterograde tracing with immunogold labeling in the rat

Abstract

The pontine nuclei (PN) and the nucleus reticularis tegmenti pontis (NRTP) are sources of an excitatory projection to the cerebellar cortex via mossy fibers and a direct excitatory projection to the cerebellar nuclei. These precerebellar nuclei, in turn, receive a feedback projection from the cerebellar nuclei, which mostly originate in the lateral nucleus (LN). It has been suggested that the feedback projection from the LN partially uses gamma-aminobutyric acid (GABA) as a transmitter. We tested this hypothesis by using a combination of anterograde tracing (biotinylated dextran amine injection into the LN) and postembedding GABA and glutamate immunogold histochemistry. The pattern of labeling in the PN and the NRTP was compared with that of cerebellonuclear terminals in two other target structures, the parvocellular part of the nucleus ruber (RNp) and the ventromedial and ventrolateral thalamus (VM/VL). The projection to the inferior olive (IO), which is known to be predominantly GABAergic, served as a control. A quantitative analysis of the synaptic terminals labeled by the tracer within the PN, the NRTP, and the VL/VM revealed no GABA immunoreactivity. Only one clearly labeled terminal was found in the RNp. In contrast, 72% of the terminals in the IO were clearly GABA immunoreactive, confirming the reliability of our staining protocol. Correspondingly, glutamate immunohistochemistry labeled the majority of the cerebellonuclear terminals in the PN (88%), the NRTP (90%), the RNp (93%), and the VM/VL (63%) but labeled only 5% in the IO. These data do not support a role for GABAergic inhibition either in the feedback systems from the LN to the PN and the NRTP or within the projections to the RNp and the VM/VL.

Cerebellum and Cerebellar Connections

“…These circuitries are found both for the mossy fiber systems but also, potentially more prominently, for the inferior olive. For instance, the reticular tegmental nucleus of the pons as well as the basal pontine nuclei receive direct input from the cerebellar nuclei and so participate in both nucleo-ponto-nuclear and in nucleo-ponto-cortico-nuclear circuits (Murakami et al, 1981;Schwarz and Schmitz, 1997). As the two constituents of the former circuit, i.e., the nucleo-pontine and the pontonuclear projections, both make use of excitatory connections, this may result in a circuit mediating reverberating activity (Tsukahara, 1972;Tsukahara et al, 1983;Mock et al, 2006).…”

Selective Modulation of Histaminergic Inputs on Projection Neurons of Cerebellum Rapidly Promotes Motor Coordination via HCN Channels

“…Note that only H2 receptor immunostainings were present in all three cerebellar nuclei. DN, dentate nucleus; FN, fastigial nucleus; IN, interpositus nucleus glutamatergic, GABAergic, or glycinergic (glycinergic ones are only reported in the FN and DN in mice) [16,[30][31][32], whereas interneurons are GABAergic and/or glycinergic [16,33]. Therefore, in the present study, we used anti-H2 receptor antibody, together with anti-vesicular glutamate transporter VGLUT2, or anti-GAD67 (a key enzyme in GABA biosynthesis) and anti-glycine transporter GLYT2 antibodies to colabel the cerebellar nuclear neurons, and observed the expression and distribution of H2 receptors in glutamatergic, GABAergic, and glycinergic neurons in all three cerebellar nuclei.…”

Afferent sources to the inferior olive and distribution of the olivocerebellar climbing fibers in cyprinids

“…In mammals GABA, aspartate, and glutamatecontaining neurons have been reported in the cerebellar nuclei (Kumoi et al, 1988;Schwarz and Schmitz, 1997), and GABAergic neurons are considered to exert inhibitory effects on olivary neurons (Fredette and Mugnaini, 1991;Kim et al, 1998). In goldfish Ϸ50% of eurydendroid cells retrogradely labeled from the base of the cerebellum were aspartate-immunopositive, while no GABA-immunopositive cells were found (Ikenaga et al, 2005).…”