Sacral Link Nuclear Accept The Morphological And Electrophysiological Evidence Of Pelvic Visceral Noxious Stimulation Incoming Links

Previous studies have suggested that the dorsal commissural nucleus (DCN) of the lumbosacral spinal cord is central for the intergration and transmission of sensory information from both somatic and visceral organs. The DCN could, therefore, represent an ideal model for studding the modulation of nociceptive signals from somatic and visceral primary afferents. Morphological and electrophysiological studies were undertaken to confirm whether visceral nociceptive inputs project to the DCN. The results were as follows:1. Expression of c-fos protein in substance P receptor-like immunoreactive neurons in response to noxious stimuli in the urinary bladder: an observation in lumbosacral cord segments ofChemical irritation of the urinary bladder with formalin in the rat induced c-fos protein-like immunoreactivity in more than 80% of substance P receptor-like immunoreactive (SPR-LI) neurons of the DCN, sacral parasympathetic nucleus and lamina I in the 6th lumbar and 1st sacral cord segments. Thus, neurons with SPR-LI may receive noxious information from the urinary bladder through primary afferent fibers containing substance P.2. Synaptic connections between substance P receptor positive neurons and SP-ergic terminals in dorsal commissural nucleus of rat lumbosacral spinal cordOur previous studies have confirmed that the DCN of the lumbosacral spinal cord receives both somatic and visceral afferent inputs. Furthermore, immunohistochemical studies have shown that the DCN contains many nerve terminals showing substance P-like immunoreactivity (SP-LI) and many neurons exhibiting immunoreactivity for the SP receptor (SPR). In order to determine whether SP-LI terminals form synaptic connections with SPR-LI neurons, we examined the ultrastructural features of SPR-LI neurons and their relationship with the SP-ergic terminals in the DCN of the rat, by using double-immunohistochemical staining for SPR and SP. Using light microscopy, both dense networks of SP-LI terminals and numerous SPR-LI perikarya and dendrites were observed in DCN; in addition, some SP-LI terminals were clearly located in close proximity to SPR-LI perikarya and dendrites. Using electron microscopy, the SPR-LI products in DCN neurons...