Compartmental function and modulation of the striatum

Sabah Bari ‘24

Figure 1. Image provided by the National Institutes of Health of an embryonic smooth muscle cell which is crucial to the development of the striatum.

The striatum is one of the main input areas of the basal ganglia, a neuronal circuit necessary for voluntary movement control. It is a critical component of motor control, action selection and reward systems within the brain. Almost all elements of the brain’s reward circuit are modulated during social behavior. The striatum has two main efferent pathways. There are 2 main efferent pathways and the organization of each greatly impacts the movement and action selection. The direct pathway, which targets Dopamine 1 receptors, promotes action selection and thalamus disinhibition. The indirect pathway that targets Dopamine 2 Receptors, and opposed the direct pathway. With the addition of direct and indirect pathways, the striatum is organized into defined compartments known as striosomes. The main purpose of this study, conducted by researchers from Stony Brook University, was to further elucidate the organization of the striatum and see the striatum in ways that were never seen before through the advancement of technology allowing us to understand the differences between striosome and matrix compartments to become clear and how these 2 compartments interact with each other based on sensory input. The matrix compartments are one of two complementary chemical compartments within the striatum.

SPNs also known as the GABAergic spiny projection neurons within the striatum affects behavior through compartment-specific activity involving selective activation of afferents, modulation of neuronal activity and synaptic transmission by neuromodulators (such as dopamine), and interneuron mediated compartmental signaling. This is important because the striatum’s role is to be able to convey these activities for normal development and expression. After early studies examining acetylcholinesterase movement in the striatum of adult humans, rhesus monkeys, and cats, it became evident that histological patterns gave insight into how the striatum was organized. They found that the patterns of organization had more to do with what neighboring neurons had in common rather than local acetylcholinesterase activities. Acetylcholine is a compound that contracts smooth muscle, dilates blood vessels, increases bodily secretions and slows down heart rate as part of the autonomic nervous system. The striatum’s compartmental organization is primary formed during early embryonic development, thus allowing a newborn baby to physically smile as their body learns how to process neurotransmitters such as serotonin, dopamine, oxytocin, and endorphins using striatum direct and indirect pathways.

Understanding the structure of the striatum and its pathways have largely been impeded by technical limitations. This is due to the low percentage of striosomal neurons and inability to visualize compartmental organization in live tissue. The study is hopeful that future development in technology will allow researchers to visualize and manipulate compartment‐specific neurons. Along with advanced technology there would be available genetic and imaging tools to grant new findings on the functional and modulatory mechanisms that shape compartment-specific activity within the striatum. 

Works cited:

[1] Prager, Eric M., and Joshua L. Plotkin. “Compartmental Function and Modulation of the Striatum.” Journal of Neuroscience Research 97, 1503-1514 (2019). https://doi.org/10.1002/jnr.24522

[2] Image retrieved from: https://search.creativecommons.org/photos/2d949630-c4ab-4ac0-ae0d-2b3c60d8969c

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