In a groundbreaking study, neuroscientists have made significant strides in understanding the relationship between two key areas of the brain, the striatum and the subthalamic nucleus (STN), both integral parts of the basal ganglia system. The study, which was performed on adult male and female mice from the Mutant Mouse Resource & Research Centers (MMRRC), delves into the detailed interaction and organization of the subthalamostriatal projections - direct axonal connections from the STN to the striatum.
To comprehend this complex interplay, the researchers implemented monosynaptic retrograde tracing from specific populations of dorsal striatal neurons. They aimed to quantify the connectivity from STN neurons to various striatal cell types, including spiny projection neurons, GABAergic interneurons, and cholinergic interneurons.
In the study, the team combined ex vivo electrophysiology and optogenetics to decipher the responses of diverse dorsal striatal neuron types to the activation of STN axons. Remarkably, their findings revealed that the connectivity from STN neurons to striatal parvalbumin-expressing interneurons was significantly higher (approximately 4 to 8 times) than that from STN to any of the other striatal cell types examined.
Further, only parvalbumin-expressing interneurons exhibited robust monosynaptic excitatory responses to subthalamostriatal inputs, corroborating the tracing studies' results. The data collectively demonstrate the selectivity of the subthalamostriatal projection for the target cell type, an important finding in neurobiology.
In summary, the study underscores the unique position of glutamatergic STN neurons, highlighting their potential to directly and powerfully influence striatal activity dynamics due to their enriched innervation of GABAergic parvalbumin-expressing interneurons. These findings, generated using mice from the MMRRC, contribute substantially to our understanding of brain dynamics and open new avenues for exploring neurological disorders and potential treatments.