Assessing memory in mice using habituation of nose-poke responding

The present experiments investigated the validity and utility of measuring the habituation of a nose-poke response to assess memory in mice. Mice were placed in an operant chamber equipped with two holes in one wall. Nose-poke responses were recorded by the interruption of a photo-beam across the openings of the holes. Responding produced no consequences. Nose-poke responding was recorded over 20 min for one-four daily sessions. Habituation, as defined by a decrease in the number of nose-pokes over time, was observed during sessions as well as between daily sessions. When the inter-session interval was increased from 1 to 8 days, habituation decayed in a time-dependent manner indicating memory was involved in the habituation phenomenon. CD-1, C57/BL and Swiss Webster X DBA mouse strains all displayed robust time-dependent habituation. Scopolamine, in CD-1 mice, dose-dependently disrupted habituation in an anterograde (0.1-1 mg/kg) and retrograde (1-10 mg/kg) procedure. The present procedure provides a rapid and novel method to assess habituation in a variety of strains of mice and may be a useful addition to existing procedures for measuring memory function in mice.