Mapping central projections of colorectal afferent fibres

This study was conducted to identify and map the distribution of sensory afferent neurons innervating the colon and their central projections. Mice underwent retrograde tracing using Cholera Toxin Subunit B (CTB) from the colon wall and four days later labelled neurons were localised within spinal dorsal root ganglia at spinal cord levels thoracic (T9-T13), lumbar (L1-L6) and sacral (S1) and within nodose/jugular ganglia complex (N/J) that were CLARITY cleared and visualised using confocal microscopy (neuronal counts data attached). Seven days later labelled fibres were localised and mapped within the spinal cord dorsal horn and the caudal medulla. Fibres were found to be in close location to neurons activated by distension of the colon and rectum (CRD). The number of neurons activated by CRD in the dorsal horn and the dorsal vagal complex were then compared following noxiuos and non-noxious colorectal stimuli relative to no stimuli to identify where colorectal afferents relay information relevant to nociceptive (pain) processing (neuronal counts data attached).