Acquisition and retention of habituation in the preweanling rat.

The acquisition and retention of habituation to air-puff was studied in rats on Days 1-19 postpartum. Animals of all ages demonstrated habituation but the rate of habituation varied with age: slower on each successive day from Day 1 to Day 8, but thereafter more rapid on each successive day. This peak of elicited responding is discussed in relation to the peak of spontaneous activity at Day 16 and to the pattern of neural development, including changes in acetylcholinesterase, norepinephrine, and serotonin, measured during the preweaning period. All ages showed 30-min retention of habituation, with 60-min retention developing after the 1st week. No evidence of 24-hr retention appeared at any age.