Relationships Between Hair-Follicle Afferent Axons and Glycine-Immunoreactive Profiles in Cat Spinal Dorsal Horn

The study explored the relationships between hair-follicle afferent axons and glycine-immunoreactive profiles in the cat spinal dorsal horn, focusing on type II glomeruli located at the lamina II/III boundary. These glomeruli were associated with electron-lucent primary afferent axons, likely from myelinated fibers, and involved axonal contacts containing both GABA and glycine, suggesting the involvement of inhibitory interneurons. It was noted that while GABA was prevalent in most boutons presynaptic to primary afferents, Aδ- and Aβ-LTMR axoaxonic boutons were particularly rich in glycine, aligning with the presence of glycinergic neurons in the deeper lamina of the dorsal horn. The study highlighted that Aβ-LTMRs formed simpler synaptic arrangements with fewer axoaxonic synapses, whereas Aδ-LTMRs exhibited more complex axoaxonic structures resembling type II synaptic glomeruli.