Dipsogenic effects of intra and extracellular thirst stimuli before and after chronic DFP treatment

The water intake of rats was observed following subcutaneous administration of intra and extracellular thirst stimuli (hypertonic saline, polyethylene glycol, angiotensin, and isoproterenol) before and after chronic treatment with the anticholinesterase agent, diisopropyl fluorophosphate (DFP), and its arachis oil vehicle. Only hypertonic saline and isoproterenol reliably increased water intake in both groups prior to chronic treatment. After chronic treatment hypertonic saline produced the same degree of water intake in the DFP-treated and control animals, but isoproterenol appeared to produce a greater degree of water intake in the DFP-treated than in the control rats. These results suggest that there are no gross disturbances in the mechanisms underlying intra and extracellular thirst stimuli following the development of tolerance to DFP.