Neurotoxic changes in cat neurohypophysis after single and multiple exposures to diisopropylfluorophosphate and soman

Fine structural changes in cat neurohypophysis have been studied after single and multiple parenteral sub-LD50 does of the organophosphates diisopropylfluorophosphate (DFP) and pinacolyl methylphosphonofluoridate (soman). While a single sub-LD50 dose of DFP does not alter fine structure, multiple exposures result in degeneration of axons. Single as well as multiple sub-LD50 doses of soman cause dilation of axons with an accumulation of neurosecretory granulated vesicles (NGVs). Increased metabolic activity is suggested by the presence of well-developed Golgi complexes and increased amounts of endoplasmic reticulum in the pituicytes of treated animals. Direct and indirect actions of DFP and soman on neurohypophysial hormone release are discussed as putative mechanisms responsible for the morphological changes in the neurohypophysis.