A new visceral nociceptive pathway in the dorsal column: Anatomical and functional studies of pancreatic pain including the effects of limited dorsal column lesions in rats

Novel neuronal pathways carrying visceral nociceptive information through the dorsal column of the spinal cord have recently been described by our group. The clinical importance of these pathways is suggested by the effectiveness of a midline dorsal column lesion in the relief of pelvic visceral pain in cancer patients. Aims: To describe the neuronal pathways mediating pain from the pancreas and to study the effectiveness of dorsal myelotomy for the relief of pancreatic pain. Methods: Neuronal tract mapping was done after small iontophoretic injections of Phaseolus vulgaris-leucoagglutinin (PHAL, 2.5% in phosphate buffer; pH 8.0) around the central canal at "1'7 or S1 spinal segments. Acute pancreatitis was induced by glyoxydecholic acid (GDOC) injection into the pancreatic duct followed by six hourly intraperitoneal injections of caerulean (72mg total). Dorsal myelotomy was performed either at the C1 or T10 level. The above procedures were done in anesthetized rats. Body weight and behavior (locomotion, exploratory and grooming) was monitored. Results: The ascending neuronal projections from the T7 or S1 spinal cord regions ascend near the dorsal intermediate and dorsal midline septi of the dorsal column, respectively. These pathways terminated primarily in the cuneate and gracile nuclei, respectively, in the caudal medulla. Some terminal fibers were found throughout the brainstem primarily in midline structures such as the pontine reticular formation, periaqueductal gray, and the medial portions of the thalamus and hypothalamus. Limbic structures, including the supramammillary nucleus, the nucleus basaiis of Meynert, and the zona incerta also contained axonal terminals. Assessment of "rearing" exploratory behavior in animals with acute pancreatitis revealed a significant decrease from controls. Normal rearing activity returned in animals after dorsal column lesions including the area near the dorsal intermediate septum. The long-term effects of dorsal myelotomy involving each of these dorsal column pathways was examined. Body weight and behavioral activity in animals with dorsal column lesions were not affected significantly at any time point through 30 weeks. Condnsions: These data demonstrate that pancreatic pain is transmitted via a dorsal column pathway. Further, a dorsal intermediate septum myelotomy may provide long term relief of such pain and is well tolerated. This research was made possible by full grant support from NIH NS 11255.