Monkey globus pallidus external segment neurons projecting to the neostriatum

Area of Science:

• Neuroscience
• Primate Neuroanatomy

Background:

• The basal ganglia circuitry plays a crucial role in motor control and learning.
• Understanding the specific projections within the basal ganglia, such as the pallidostriatal pathway, is essential for elucidating its functional mechanisms.

Purpose of the Study:

• To quantify the number and parvalbumin (PV) immunoreactivity of neurons in the globus pallidus external segment (GPe) that project to the neostriatum in macaque monkeys.
• To investigate the contribution of PV-immunoreactive neurons to the pallidostriatal projection.

Main Methods:

• Anterograde tracing using WGA-HRP injections into the caudate nucleus and putamen of macaque monkeys (Macaca mulatta and M. fuscata).
• Immunohistochemical staining to identify parvalbumin (PV) immunoreactivity in labeled neurons.
• Stereological counting of retrogradely labeled GPe neurons and PV-immunoreactive neurons.

Main Results:

• A significant proportion of globus pallidus external segment (GPe) neurons were labeled following WGA-HRP injections into the neostriatum, indicating a substantial pallidostriatal projection.
• Approximately 30% of GPe neurons were found to project to the neostriatum.
• Around two-thirds of these pallidostriatal neurons exhibited parvalbumin (PV) immunoreactivity.

Conclusions:

• A substantial number of primate GPe neurons project to the neostriatum.
• A significant portion of the pallidostriatal projection originates from PV-immunoreactive neurons.
• The pallidostriatal pathway, particularly its PV-immunoreactive component, should be considered in functional analyses of basal ganglia circuitry.