Fig 2: Expression of 5-HT in relation to myelin basic protein (MBP), SP and CGRP. A MBP showed a distinct staining of myelin sheath flanking cross-sectioned Aδ-fibre axons. A robust MBP-ir was observed (Arrowhead) between the Aδ-fibre axon and Schwann cell neurolemma. An irregular, and sometimes faint, expression of 5-HT could be observed in Aδ-fibre axons (Asterix) and just outside the myelin sheath (Arrow), indicative for the neurolemma of the Schwann cell containing its cytoplasm. B A minority of observed C-fibres expressed 5-HT-ir, these were more frequently found in proximity to Redlich-Obersteiner’s zone. CGRP-ir was more abundantly expressed in C-fibres and did not co-localize with 5-HT. Arrows mark 5-HT positive C-fibre boutons and arrowheads mark CGRP positive C-fibre boutons. Insert: Two thin C-fibres entwining and differentially expressing either CGRP or 5-HT. C Similarly, SP could be found concentrated to C-fibre boutons (Arrowhead) throughout the TG. The few 5-HT positive C-fibres (Arrow) were not found to co-localize with SP positive C-fibres. Insert: A thin C-fibre expressing 5-HT-ir (Arrow) above a seemingly larger SP positive C-fibre (Arrowhead)