Cortical inputs to m2-immunoreactive striatal interneurons in rat and monkey

Area of Science:

• Neuroscience
• Cell Biology
• Neuroanatomy

Background:

• Previous studies failed to anatomically confirm cortical inputs to striatal cholinergic and somatostatinergic interneurons.
• Electrophysiology suggested monosynaptic cortical excitation of cholinergic interneurons.
• Incomplete labeling of distal dendrites was hypothesized as a reason for negative anatomical findings.

Purpose of the Study:

• To reinvestigate cortical inputs to cholinergic and somatostatinergic striatal interneurons.
• To utilize m2 muscarinic receptor antibodies as a marker for these interneurons.
• To combine anatomical tracing with cortical manipulations in rats and monkeys.

Main Methods:

• Used m2 muscarinic receptor antibodies to identify cholinergic and somatostatinergic interneurons in the striatum.
• Injected biotinylated dextran amine (BDA) tracer into the monkey prefrontal cortex.
• Performed aspiration lesions of the sensorimotor cortex in rats.

Main Results:

• A small percentage (1-2%) of cortical terminals formed asymmetric synaptic contacts with m2-immunoreactive interneurons in the striatum.
• The majority of these cortical synapses were located on small dendritic spines or spine-like appendages.
• Both rats and monkeys showed similar patterns of cortical innervation.

Conclusions:

• Cholinergic and somatostatinergic interneurons in the striatum receive direct cortical inputs.
• These inputs, though sparse, can modulate neuronal activity due to the intrinsic properties of the interneurons.
• This clarifies a pathway for cortical information integration and modulation within the striatum.