Preoperative enrichment and behavioral recovery in rats with septal lesions

To assess the behavioral effects of preoperative differential housing male rats were placed in either enriched or isolated environments at weaning prior to receiving either sham operations or septal lesions when 57 days of age. Rats with septal lesions showed reduced habituation of ambulation and initially made fewer rears in an empty open field but made more object-contacts coupled with a lack of habituation in the object-filled field. Septal rats also showed severe impairments when tested in a 12-arm radial maze with 7 arms baited and 5 arms unbaited. Preoperative enrichment did not significantly affect these lesion-induced changes. Nevertheless, enrichment significantly lowered ambulation (but did not affect habituation) in the open field and increased the number of manipulatory relative to nonmanipulatory contacts. However, preoperatively enriched septal rats showed a deficit in spontaneous alternation (45%) in contrast to the high levels (83%) shown by intact enriched rats, whereas both intact and septal isolated rats showed similar levels of spontaneous alternation (68%). These results conflict with earlier reports that preoperative enrichment "protects" rats against the deficits produced by septal lesions.