Significant changes in monoamines in rat brain induced by exposure to methyl bromide

Rats were exposed to methyl bromide (MB) gas for 24 hr or 3 weeks continuously. Norepinephrine (NE), dopamine (DA), serotonin (5-HT), acetylcholine (ACh), cyclic AMP (cAMP) and cyclic GMP (cGMP) contents in dissected brain regions were measured after MB exposure. MB produced remarkable reduction in NE contents of hypothalamus and cortex + hippocampus at 100 ppm or higher concentration after 24 hr exposure and at 10 ppm after 3 weeks exposure. At the same concentration of MB, DA, 5-HT and ACh contents were only slightly affected by the exposure. Change in neurotransmitter content was specific to NE. MB-induced changes in NE contents lasted for at least 24 hr after the cessation of exposure. cAMP was increased and cGMP was reduced by MB exposure. These results suggested that MB might have enhanced the stimulation of DA receptors and weakened the stimulation of ACh receptors in the brain.