SKIN-VISCERAL DIVERGENT PROJECTIONS OF CHOLE CYSTOKININ-CONTAINING DORSAL ROOT GANGLION NEURONS: A TRIPLE-LABELLING STUDY WITH FLUORESCENT TRACERS AND IMMUNOHISTOCHEMISTRY / 解剖学报

ABSTRACT

Skin-visceral divergent projections of cholecystokinin(CCK)-containing dorsal root ganglion neurons were studied by combined technique of fluorescent double-labelling and immunohistochemistry. Fast Blue(FB) and Nuclear Yellow (NY) were injected into the coeliac ganglion and the cutaneous branches of left 9th-11th intercostal nerves, respectively. Three kinds of neurons labelled with fluorescein were observed in T_(9-11) dorsal root ganglia under Nikon fluorescence microscope with 365 nm excitation light: FB-labelled neurons with blue-fluorescing cytoplasm; NY-labelled neurons with yellow-fluorescing nucleus and double-labelled neurons with blue cytoplasm and yellow nucleus. The double-labelled neurons were found to be 2.8％ of total labelled neurons.The sections containing fluorescein labelled neurons were then stained by CCKimmunohistochemical procedure. Four kinds of neurons could be identified: NY-neurons, with CCK-immunoreactivity (NY+CCK); FB-neurons with CCK-immunoreactivity(FB + CCK);NY + FB neurons with CCK-immunoreactivity(NY + FB + CCK); Single CCK-positive neurons. NY + FB + CCK triple-labelled neurons accounted for approximately 11.5％ of NY + FB double-labelled neurons,and 0.4％ of all CCK-positive neurons.The findings clearly indicated that the peripheral processes of some sensory dorsal root ganglion neurons project divergently to both skin and visceral structure, and contain CCK. The present results suggest that the peripheral dichotomization of the dorsal root ganglion nearons might converge sensory inputs from both skin and visceral fields, and thus not only provide one of the structural basis for the referred pain but also reveal that CCK might play a mediation role in the skin-visceral reflection and referred pain.