Functional development of central nervous system in the rat: ontogeny of nociceptive thresholds.

The functional development of central nervous system (CNS) in the rat has been studied from the 10th to the 45th postnatal day, through a sensory function: nociception. Baseline pain responsiveness has been assessed with the tail-flick procedure. The mean tail-flick latency clearly decreases from the 10th to the 25th day, and remains stationary from this age to 45 days. The maturational processes underlying these reductions of tail-flick latencies in developing rats are discussed.