Effects of chronic pain on learning and memory and morphological structure of hippocampus in neonatal rats / 中华麻醉学杂志

ABSTRACT

Objective It has been shown that strong acute stress or long-term chronic stress significantly affects learning and memory. The aim of this study was to investigate the effects of chronic pain on learning and memory and morphological structure of hippocampus in neonatal rats.Methods Sixty SD rats aged 7 days were randomly divided into two groups (A) chronic pain group ( n = 30) in which 0.5% formalin 0.1 ml was injected subcutaneously into plantar region of hind paw every day for two weeks and (B) control group (n = 30) in which the plantar region of hind paw was touched with cotton-tipped swab every day for 2 weeks instead of subcutaneous injection of formalin. Morris water maze performance was used to test learning and memory. The number of granule neurons in dentate gyrus and pyramidal neurons in CA3 were counted. Results The mean latency period in the Morris water maze intelligence test was significantly longer in chronic pain group than that in control group ( P