A STEREOLOGICAL STUDY OF DORSAL-ROOT GANGLION-CELLS AND NERVE ROOT FIBERS FROM RATS EXPOSED TO MERCURY-VAPOR

Although mercury vapor is known to produce tremor and peripheral neuro pathy, neuropathological studies of the effects of the vapor are few i n number. The aim of the present study has been to evaluate the effect of mercury vapor on the morphology of the dorsal root ganglion and th e spinal nerve roots. Adult male rats were exposed to mercury vapor fo r 33 days. The exposed rats developed somatic signs of intoxication an d became increasingly irritable. The total numbers and volumes of A- a nd B-cell perikarya in the dorsal root ganglia, the total number of my elinated axons in the roots, and the cross-sectional areas of axon and myelin in the nerve roots were estimated using unbiased stereological principles. The mean cross sectional area of myelin associated with n erve fibers in dorsal nerve roots of the exposed group was significant ly reduced by 20% (2P = 0.014). A tendency towards a reduction was see n in axon area of myelinated nerve fibers in the dorsal nerve roots (2 P = 0.087) and in the total numbers and mean volume of A-cell perikary a (2P = 0.059 and 2P = 0,087, respectively). No differences between th e two test groups were found for any of the parameters measured in B-c ells and ventral nerve roots. It is concluded that mercury vapor, in a dose sufficient to produce intoxication, induces only minor changes i n dorsal root ganglion and nerve roots in rats.