Effects of methimazole on the rat olfactory system: An anatomical and behavioral analysis

Rats were trained and tested on a variety of olfactory detection and discrimination problems before and after intraperitoneal injection of 300mg/kg methimazole. Relative to controls, experimental animals demonstrated a modest decrement on an initial odor detection task and on more difficult odor mixture discrimination tasks. For the anatomical study, anterograde transport of horseradish peroxidase from olfactory epithelium to the bulb was examined 1, 2, 3, or 5 days after administration of methimazole. The toxicant resulted in between approximately 10% and 30% disruption of anterograde transport of HRP from epithelium to bulbs in a time-dependent manner with 5 day experimental rats tracing the greatest disruption. There was an inverse relationship between behavioral recovery and the progressive loss of anterograde transport of HRP from the epithelium to the bulbs. These results suggest that the observed moderate olfactory sensory input.