Abstract
SummaryIndirect pathway medium-sized spiny neurons (iMSNs) in the neostriatum are well known to project to the external segment of the globus pallidus (GPe). Although direct MSNs (dMSNs) also send axon collaterals to the GPe, it remains unclear how dMSNs and iMSNs converge within the GPe. Here, we selectively labeled neighboring dMSNs and iMSNs with green and red fluorescent proteins using an adeno-associated virus vector and examined axonal projections of dMSNs and iMSNs to the GPe in mice. Both dMSNs and iMSNs formed two axonal arborizations displaying topographical projections in the dorsoventral and mediolateral planes. iMSNs displayed a wider and denser axon distribution, which included that of dMSNs. Density peaks of dMSN and iMSN axons almost overlapped, revealing convergence of dMSN axons in the center of iMSN projection fields. These overlapping projections suggest that dMSNs and iMSNs may work cooperatively via interactions within the GPe.
Highlights
The neostriatum, caudate-putamen (CPu), is the major input nucleus of the basal ganglia, which plays a key role in motor control (Albin et al, 1989; DeLong, 1990) and receives excitatory inputs mainly from the cerebral cortex and thalamus (Alexander and Crutcher, 1990)
SUMMARY Indirect pathway medium-sized spiny neurons in the neostriatum are well known to project to the external segment of the globus pallidus (GPe)
We selectively labeled neighboring direct Medium-sized spiny neurons (MSNs) (dMSNs) and Indirect pathway medium-sized spiny neurons (iMSNs) with green and red fluorescent proteins using an adeno-associated virus vector and examined axonal projections of dMSNs and iMSNs to the GPe in mice. Both dMSNs and iMSNs formed two axonal arborizations displaying topographical projections in the dorsoventral and mediolateral planes. iMSNs displayed a wider and denser axon distribution, which included that of dMSNs
Summary
The neostriatum, caudate-putamen (CPu), is the major input nucleus of the basal ganglia, which plays a key role in motor control (Albin et al, 1989; DeLong, 1990) and receives excitatory inputs mainly from the cerebral cortex and thalamus (Alexander and Crutcher, 1990). Accumulating evidence supports coordinated interactions between the direct and indirect pathways (Peak et al, 2019; Tecuapetla et al, 2014): for example, dMSNs and iMSNs can be cooperatively activated during motor action initiation (Cui et al, 2013). These findings indicate that the direct and indirect pathways are not always competing but that a structural basis for the coordinated functions of dMSNs and iMSNs may underlie motor control by the basal ganglia
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