Age, sex and strain comparison of habituation of the startle response in the rat.

Habituation and sensitization of the acoustic startle response were studied in young (3 month) and aged (26 month) male and female Fischer 344 rats and in young (3 month) and aged (32 month) male Sprague Dawley rats. Tones were presented on 25 consecutive trials for a session, one session on each of four consecutive days. An air puff stimulus immediately preceded trial 20 on each day to test sensitization. All aged rats demonstrated greater short-term (within session) relative habituation than their younger counterparts. Across sessions, aged male rats of both strains habituated more quickly than younger males. Aged female rats habituated more slowly. Sensitization was more likely to occur in younger rats.