Effects of physostigmine on novelty-related location preferences

Novelty-related location preferences and activity in an exploration box were recorded for male and female Wistar albino rats following intraperitoneal injections of 0.04 or 0.08 mg/kg of either physostigmine or neostigmine. Although rearing was reduced by the highest dose of both drugs and ambulation was reduced by the same dose of neostigmine, neither agent affected the significant preferences for novelty that typified all subjects. In a second experiment designed to assess the effects of 0.08 mg/kg of the two drugs administered during rather than after confinement to the familiar half of the apparatus, neostigmine reduced rearing, walking, and ambulation while increasing defecation, but physostigmine did not affect any response. While some minor motor impairment may have arisen from its peripheral effects, the lack of changes in novelty-related location preferences failed to support facilitation of either novelty avoidance or habituation by physostigmine suggested in previous studies.