Complementary distribution of glutamatergic cerebellar and GABAergic basal ganglia afferents to the rat motor thalamic nuclei

Abstract

Motor thalamic nuclei, ventral anterior (VA), ventral lateral (VL) and ventral medial (VM) nuclei, receive massive glutamatergic and GABAergic afferents from the cerebellum and basal ganglia, respectively. In the present study, these afferents were characterized with immunoreactivities for glutamic acid decarboxylase of 67 kDa (GAD67) and vesicular glutamate transporter (VGluT)2, and examined by combining immunocytochemistry with the anterograde axonal labeling and neuronal depletion methods in the rat brain. VGluT2 immunoreactivity was intense in the caudodorsal portion of the VA-VL, whereas GAD67 immunoreactivity was abundant in the VM and rostroventral portion of the VA-VL. The rostroventral VA-VL and VM contained two types of GAD67-immunopositive varicosities (large and small), but the caudodorsal VA-VL comprised small ones alone. VGluT2-immunopositive varicosities were much larger in the caudodorsal VA-VL than those in the rostroventral VA-VL and VM. When anterograde tracers were injected into the basal ganglia output nuclei, the vast majority of labeled axon varicosities were large and distributed in the rostroventral VA-VL and VM, showing immunoreactivity for GAD67, but not for VGluT2. Only the large GAD67-immunopositive varicosities were mostly abolished by kainic acid depletion of substantia nigra neurons. In contrast, large to giant axon varicosities derived from the deep cerebellar nuclei were distributed mostly in the caudodorsal VA-VL, displaying VGluT2 immunoreactivity. The VGluT2-positive varicosities disappeared from the core portion of the caudodorsal VA-VL by depletion of cerebellar nucleus neurons. Thus, complementary distributions of large VGluT2- and GAD67-positive terminals in the motor thalamic nuclei are considered to reflect glutamatergic cerebellar and GABAergic basal ganglia afferents, respectively.

Thalamic interactions of cerebellum and basal ganglia

“…In both instances, labeled neurons were also found in the DCN. Recent histochemical evidence supports the notion of complementary cerebellar and basal ganglial territories in that glutamate and GABA receptors were found in complementary densities in the thalamus (Kuramoto et al 2010). The presented evidence suggests that territories of cerebellar and basal ganglia projections are mainly segregated in the rat thalamus.…”

Functioning of Circuits Connecting Thalamus and Cortex

“…Afferents to the ventral anterior/ventral lateral motor thalamic complex from the cerebellum have the anatomical features of large terminals that often participate in triadic relationships (82,83), and this marks these afferents as drivers [(reviewed in (148)]; these branch to also innervate the red nucleus and tegmental reticular nucleus (19,103,150) (Fig. 13B).…”

Anatomical localization of Cav3.1 calcium channels and electrophysiological effects of T-type calcium channel blockade in the motor thalamus of MPTP-treated monkeys

“…The borders between the basal ganglia-and cerebellar-receiving territories of the ventral motor nuclei were delineated using adjacent Nissl-stained sections (1 section out of 6) combined with drawings of corresponding levels from two rhesus monkey brain stereotaxic atlases (Lanciego and Vazquez 2012;Paxinos et al 1999). In addition, one out of six sections was immunostained for the vesicular glutamate transporter 2 to confirm further the border of the cerebellar-receiving region of the ventrolateral nucleus of the thalamus (Kuramoto et al 2011;Villalba et al 2006). As controls, sections of the thalamus adjacent to those processed to localize Ca v 3.1 immunoreactivity were incubated in solutions, in which the primary MAb were replaced by nonimmune mouse serum.…”