The Effect of Neonatal Inflammatory Pain on Cognitive Processes and Reactivity of the Hypothalamic–Pituitary–Adrenal Axis in Prepubertal Rats

• Published in: Journal of evolutionary biochemistry and physiology Vol. 57; no. 5; pp. 1031 - 1039
• Main Authors: Mikhailenko, V. A., Butkevich, I. P., Vershinina, E. A.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.09.2021; Springer Nature B.V
• Subjects: Animal Physiology; Biochemistry; Biomedical and Life Sciences; Cognitive ability; Corticosterone; Evolutionary Biology; Experimental Papers; Hypothalamic-pituitary-adrenal axis; Hypothalamus; Inflammation; Juveniles; Life Sciences; Long term memory; Memory; Neonates; Pain; Pituitary; Rodents; Sexual dimorphism; Spatial discrimination learning; Spatial memory; late prepubertal period; rat; corticosterone; neonatal inflammatory pain; cognitive processes
• ISSN: 0022-0930; 1608-3202
• DOI: 10.1134/S0022093021050057

We investigated the effect of neonatal inflammatory pain on the dynamics of plasma corticosterone level in newborn rat pups and, in the late prepubertal period (days 45–53), the processes of spatial learning and memory, as well as the reactivity of the hypothalamic–pituitary–adrenal (HPA) axis to forced swim stress, in male and female rats. We found a long-term increase in HPA axis reactivity in response to peripheral inflammatory pain induced by formalin injection to newborn rat pups, which suggested the developmental modification of the HPA axis and its possible involvement in the regulation of cognitive abilities. Neonatal pain caused a deficit in spatial learning and memory, revealing a sexual dimorphism in the implementation of these processes. After recording long-term memory in 53-day-old rats in the forced swim test, the plasma corticosterone was found to be increased compared to the basal level, however, no differences in the hormone level were detected both in rats with neonatal pain vs. control animals and in males vs. females. Thus, in the late prepubertal period, rats showed no direct relationship between neonatal pain-induced activation of the HPA axis and the indices of spatial learning and memory, which may indicate the involvement of other neurobiological systems in the effect of neonatal pain on cognitive abilities.