An Immunohistochemical Analysis on The Human Cerebellar Dopaminergic System

Abstract

Background The cerebellum now it has not considered a dopaminergic region. Despite, is traditionally reported only the presence of dopaminergic afferents to the cerebellum. Currently, studies attribute to the cerebellum a critical role in motor and cognitive functions and suggest a cerebellar involvement in dopamine related neurologic and psychiatric disorders. In several studies has been demonstrated mainly in the cerebellum of rodents a widely distribution of all dopaminergic receptor subtypes (DRD1-DRD5), a poor number of dopaminergic Purkinje neurons, and the presence of several dopaminergic neurons in the deep cerebellar nuclei. Data on an intrinsic dopaminergic neuronal system in the human cerebellum are lacking. Methods The aim of the present study of chemical neuroanatomy was to investigate in human cerebellum on the presence of a dopaminergic neuronal system, through an immunohistochemical approach based on the use of specific antibodies against the dopamine membrane transporter (DAT) and the dopamine receptor subtype 2 (DRD2). Results The immunoreactions revealed the presence of DAT and DRD2 positive neuronal cell bodies and processes of all the layers of the cerebellar cortex and in the dentate nucleus. These results are in agreement with previous studies, and suggest which the intrinsic cerebellar neuronal dopaminergic system may be involved in intrinsic and extrinsic (projective) cerebellar circuits. Conclusions This study open a new scenario on the interpretation of the cerebellar role in dopaminergic related brain disorders. Finally, this study may be an innovative critical element for the development of pharmacologic and non-pharmacologic therapeutic strategies for neurologic and psychiatric disorders related to dopamine.

The Cerebellar Dopaminergic System

“…In the human cerebellum, immunohistochemical experiments revealed the presence of DAT immunoreactive fibers and neuronal cell bodies in lobules VII and IX (crus I and II, ansiform lobules, and tonsilla) and in the dentate nucleus (Table 1; Figures 1, 2; Flace, 2017Flace, , 2019bFlace, , 2020Flace et al, 2018aFlace et al, , 2019bFlace et al, , 2020. There is a significant presence of DAT immunoreactive dendritic arborization of the Purkinje neurons in the molecular layer of the human cerebellar cortex (Table 1; Figure 1).…”

“…Moreover, DAT immunoreactive nerve fibers variously oriented in the subcortical white substance, has been detected (Figure 1; Flace et al, 2019aFlace et al, ,b, 2020. In the dentate nucleus, the DAT immunoreactivity in neuronal cell bodies and processes of different neuron types has been detected (Table 1; Figure 3); the small neuron type is involved in intrinsic circuits, the medium neuron type (Table 1; Figure 3) mainly involved in intrinsic and also in extrinsic circuits, and four different large neuron types, which include the central neuron, the border neuron, the intermediate asymmetrical neuron, and the intermediate fusiform neuron, involved in projective circuits of the dentate nucleus (data not showed; Chan-Palay, 1977;Maric, 2010;Ristanović et al, 2010;Flace et al, 2017Flace et al, , 2019bFlace et al, , 2020Flace, 2018). Dopamine transporter immunoreactivity in neuronal cell bodies and processes of the perivascular neuron type has also been observed, a neuron type may be involved in regulatory mechanisms of blood-brain barrier (BBB) permeability and in volume transmission mechanisms (data not showed; Flace et al, 2004;Ambrosi et al, 2007;Flace, 2017Flace, , 2018Flace, , 2019bFlace, , 2020.…”

“…Chemical neuroanatomy studies on the detection of dopaminergic neuronal elements in the cerebellum of mammals (including human) makes use of direct antisera against DA and of [ 3 H]-dopaminergic ligands (Panagopoulos et al, 1991;Panagopoulos and Matsokis, 1994) or antisera against the specific dopaminergic marker, the dopamine transporter (DAT), the plasma membrane monoamine transporter involved in DA synaptic reuptake (Table 1; Melchitzky and Lewis, 2000;Dunnet et al, 2005;Giompres and Delis, 2005;Delis et al, 2008;Kim et al, 2009;Flace et al, 2019bFlace et al, , 2020, the indirect marker of the dopaminergic neurotransmission, the dopamine and adenosine 3 ′ -5 ′ -monophosphate (cAMP)-regulated protein Mr 32,0000 (DARPP-32), a protein phosphatase-1 inhibitor involved in dopaminergic neuronal synaptic signaling (Table 1; Alder and Barbas, 1995;López et al, 2010;Nishi and Shuto, 2017), or, indirectly, by means of antisera against not elective markers for DA, such as tyrosine hydroxylase (TH), the rate-limiting enzyme DA biosynthesis, which catalyzes the conversion of L-tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA) (Table 1; Ikai et al, 1992;Fujii et al, 1994;Melchitzky and Lewis, 2000;White and Thomas, 2012) and vesicular monoamine transporter 2 (VMAT 2 ), the synaptic vesicles transporter of monoamine neurotransmitters such as DA, NA, 5-HT, and histamine (HIS) (Table 1; Kim et al, 2009;Lawal and Krantz, 2013).…”

“…There is a significant presence of DAT immunoreactive dendritic arborization of the Purkinje neurons in the molecular layer of the human cerebellar cortex (Table 1; Figure 1). Moreover, the DAT immunoreactivity has been detected in form of clusters in the neuropil among the space of Held, the sites of the cerebellar glomeruli (Table 1; Figure 1; Flace, 2017Flace, , 2019bFlace, , 2020Flace et al, 2018aFlace et al, , 2019bFlace et al, , 2020.…”

“…In addition, the DAT immunoreactivity in the cell bodies of Purkinje neurons and of synarmotic neurons (Neuron of Landau) has been also detected (Table 1; Figure 1). This latter, one of the non-traditional large neuron granular layers was involved in corticocerebellar and in corticonuclear projective circuits (Flace et al, 2004(Flace et al, , 2018a(Flace et al, , 2019b(Flace et al, , 2020Ambrosi et al, 2007;Flace, 2017Flace, , 2019aFlace, ,b, 2020. The DAT immunoreactivity in the cell bodies of few granules has been also detected (Flace et al, 2019a(Flace et al, ,b, 2020.…”