Effects of prenatal stress on formalin-induced acute and persistent pain in adult male rats.

Abstract

Behavioral responses of 90-day-old male offspring from female Wistar rats exposed to restraint stress during the last week of pregnancy were studied in the formalin test. Specific biphasic behavioral response characterized acute (phase 1) and persistent tonic pain (phase 2). The intensity of nociceptive responses (evaluated by the number of flexions + shakings and by the duration of paw licking) in prenatally stressed rats changed only during phase 2. During interphase, facilitation of the flexion + shakings pattern (but not the licking pattern) in response to nociceptive stimulation was seen. The response intensity during phase 1 and the duration of both phases remained unchanged. Our findings suggest that prenatal stress modulates nociceptive sensitivity in 90-day-old offspring: it affects the duration of tonic (inflammatory), but not of acute pain. It is concluded that different mechanisms are responsible for the effects of prenatal stress on acute and persistent pain in the formalin test.