Degeneration and regeneration of the olfactory epithelium after olfactory bulb ablation in the pig: a morphological and electrophysiological study.

The olfactory bulbs were removed surgically from Large White male and female pigs, 10--12 weeks of age. At intervals of 3, 7, 14, 42 and 84 d after bulbectomy, the pigs were sacrificed and portions of olfactory mucosa were removed from the ethmoturbinate and septum regions of the nasal cavity; olfactory mucosa was also removed from unoperated pigs. A piece of each tissue sample was processed for light microscopy. The remaining tissue was placed in Ringer-Locke solution, saturated with O2/CO2 at room temperature, and the electrical activity of the olfactory epithelium was investigated in vitro by passing a stimulus of butyl acetate vapour over the epithelium. Slow negative potential changes (electro-olfactogram, e.o.g.) induced by butyl acetate were recorded. During the first two weeks after bulbectomy there was a rapid decrease in the height of the olfactory epithelium associated with the disappearance of the e.o.g. response. However by 42 and 84 d after bulbectomy, partial recovery of the height and some electrical activity of the olfactory mucosa had occurred. In some pigs, the insertion of a stainless steel lining over the cribriform plate to prevent any association of regenerating axons with forebrain tissue had no effect on the regenerative characteristics studied.