The external globus pallidus: progress and perspectives

The external globus pallidus (GPe) of the basal ganglia is in a unique and powerful position to influence processing of motor information by virtue of its widespread projections to all basal ganglia nuclei. Despite the clinical importance of the GPe in common motor disorders such as Parkinson's disease, there is only limited information about its cellular composition and organizational principles. In this review, recent advances in the understanding of the diversity in the molecular profile, anatomy, physiology and corresponding behaviour during movement of GPe neurons are described. Importantly, this study attempts to build consensus and highlight commonalities of the cellular classification based on existing but contentious literature. Additionally, an analysis of the literature concerning the intricate reciprocal loops formed between the GPe and major synaptic partners, including both the striatum and the subthalamic nucleus, is provided. In conclusion, the GPe has emerged as a crucial node in the basal ganglia macrocircuit. While subtleties in the cellular makeup and synaptic connection of the GPe create new challenges, modern research tools have shown promise in untangling such complexity, and will provide better understanding of the roles of the GPe in encoding movements and their associated pathologies.     

Reduced calcium binding protein immunoreactivity induced by electroconvulsive shock indicates neuronal hyperactivity, not neuronal death or deactivation

Calcium-binding proteins (CBPs), such as parvalbumin and calbindin D-28k, are useful markers of specific neuronal types in the CNS. In recent studies, expression of CBPs may be indicative of a deactivated neuronal state, particularly epilepsy. However, it is controversial whether altered expression of CBPs in the hippocampus practically indicate neuronal activity. Therefore, the present study was performed to investigate the extent of profiles of expression of CBPs in the rat hippocampus affected by several episodes induced by electroconvulsive shock. In the present study, following electroconvulsive shock expression of CBPs were reduced in the hippocampus in a stimulus-dependent manner, and recovered to the control level at 6 h after electroconvulsive shock. However, paired-pulse responses of the dentate gyrus were transiently impaired by electroconvulsive shock, and immediately normalized to baseline value. In addition, effects of electroconvulsive shock on expression of CBPs and paired-pulse responses were prevented by pretreatment of vigabatrin. These findings suggest that reduced expression of CBPs induced by seizure activity may be indicative of hyperactivity of CBP positive neurons, which is a practical consequence of the abnormal discharge, and that they may play an important role in regulating seizure activity.     

Effects of beta-amyloid peptide on the density of M2 muscarinic acetylcholine receptor protein in the hippocampus of the rat: relationship with GABA-, calcium-binding protein and somatostatin-containing cells

Aims: The deposition of amyloid peptides (Aβ) in the cortex and hippocampus is the primary trigger of Alzheimer's disease (AD). Recent studies also indicated that the M2 subtype of muscarinic acetylcholine receptors (M2mAChR) may be a key molecule involved in cognitive dysfunction. Thus, the purpose of this study was to determine the effects of extracellular deposition of Aβ on the density of M2mAChR in the hippocampus of the rat by M2mAChR‐immunohistochemistry. Methods: Special attention was paid to discerning any interaction between Aβ and M2mAChR in GABA‐, and calcium‐binding protein containing cells by double‐labelling immunohistochemistry. Densitometric analysis of M2mAChR‐immunoreactivity was performed using Scion Image Beta Software. Quantitative analysis of GABA‐, and calcium‐binding protein interneurones containing M2mAChR protein was performed using a NeuroLucida morphometric system. Results: Injections of Aβ into the retrosplenial cortex resulted in a significant reduction in M2mAChR‐immunoreactivity in the CA1 ipsilateral to the Aβ‐injected side as compared with the corresponding hemisphere of non‐treated control animals and with that in the corresponding region of the CA1 in the phosphate‐buffered saline‐injected side. Co‐localization studies showed that the M2mAChR is localized in a subset of GABA‐positive cells of the hippocampus, in cells that contain calcium‐binding proteins, and in a subpopulation of cells that contain the neuropeptide somatostatin. Conclusions: Our findings suggest that Aβ induces a significant reduction in M2mAChR‐immunoreactivity in the CA1 of the hippocampus and a reduction in GABAergic interneurones containing M2mAChR, which may contribute to impairment of GABAergic synaptic transmission in area CA1 of hippocampus.     

The spinal precerebellar nuclei: Calcium binding proteins and gene expression profile in the mouse

We have localized the spinocerebellar neuron groups in C57BL/6J mice by injecting the retrograde neuronal tracer Fluoro-Gold into the cerebellum and examined the distribution of SMI 32 and the calcium-binding proteins (CBPs), calbindin-D-28K (Cb), calretinin (Cr), and parvalbumin (Pv) in the spinal precerebellar nuclei. The spinal precerebellar neuron clusters identified were the dorsal nucleus, central cervical nucleus, lumbar border precerebellar nucleus, lumbar precerebellar nucleus, and sacral precerebellar nucleus. Some dispersed neurons in the deep dorsal horn and spinal laminae 6–8 also projected to the cerebellum. Cb, Cr, Pv, and SMI 32 were present in all major spinal precerebellar nuclei and Pv was the most commonly observed CBP. A number of genes expressed in hindbrain precerebellar nuclei are also expressed in spinal precerebellar groups, but there were some differences in gene expression profile between the different spinal precerebellar nuclei, pointing to functional diversity amongst them.     

大鼠脑干内三叉神经本体觉中枢通路中小白蛋白样阳性神经元的分布与发育

应用免疫组织化学技术对脑干内三叉神经本体觉中枢通路中PV样阳性神经元的分布与发育进行了观察。结果发现 :①早在胚胎 13d时 ,首先在三叉神经中脑核 (Vme)内观察到许多含小白蛋白 (Parvalbumin ,PV)样阳性神经元 ,主要为大的假单极神经元 ,呈中等阳性反应。②生后 3d时 ,Vme内PV样阳性神经元的数量明显增多 ,免疫反应呈强阳性 ,并可观察到Probst束呈强阳性反应。③生后 10d时 ,在三叉神经脊束核吻侧亚核背内侧部 (Vodm)及三叉神经感觉主核背内侧部 (Vpdm)均出现少量中等强度的PV样阳性神经元。④生后 14d时 ,三叉神经脊束核吻侧亚核邻接的外侧网状结构 (LRF) ,三叉上核尾外侧部 (Vsup CL) ,三叉神经运动核腹侧区 (AVM )及上橄榄核背侧区 (ADO)均出现PV样阳性神经元。⑤生后 2 1d时 ,Vodm和LRF(Vodm -LRF)区、“带状区”包括Vpdm ,Vsup CL ,ADO ,AVM及Probst束内的PV样阳性神经元及纤维的分布均达成年大鼠水平。上述结果表明 ,大鼠脑干内三叉神经本体觉中枢通路中PV样阳性神经元的分布、发育以及PV样阳性纤维的形成可能与胚胎及生后发育期该通路中神经元的功能成熟有关