Serotoninergic afferents in the monkey neostriatum

Area of Science:

• Neuroscience
• Cell Biology
• Neuroanatomy

Background:

• The neostriatum receives input from various extrinsic sources.
• The precise morphology and function of serotoninergic afferents in the neostriatum are not fully elucidated.

Purpose of the Study:

• To morphologically characterize serotoninergic axons in the macaque neostriatum.
• To investigate the synaptic and non-synaptic release mechanisms of serotonin in this brain region.

Main Methods:

• Golgi staining and electron microscopy were employed to visualize neuronal structures.
• Immunocytochemistry with an anti-serotonin antibody and peroxidase-antiperoxidase complex was used for specific labeling.
• Morphological analysis focused on axon arborization, varicosities, synaptic vesicles, and synapse types.

Main Results:

• Thin, extrinsic axons with profuse, beaded arborizations were observed in the neostriatum.
• Some of these axons showed specific immunoreactivity for serotonin.
• Labeled profiles formed asymmetric axospinous synapses with small dendritic spines, while others showed non-synapsing varicosities.

Conclusions:

• The study provides detailed morphological features of serotoninergic axons in the neostriatum.
• Serotonin may be released as a neurotransmitter from synapsing boutons and as a neuromodulator from non-synapsing varicosities.
• This dual release mechanism could correlate with differential effects mediated by serotonin receptors.