RT Journal Article
SR Electronic
T1 Advanced age attenuates the antihyperalgesic effect of morphine and decreases μ-opioid receptor expression and binding in the rat midbrain Periaqueductal Gray in male and female rats
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2020.06.16.154740
DO 10.1101/2020.06.16.154740
A1 Evan F. Fullerton
A1 Myurajan Rubaharan
A1 Mary C. Karom
A1 Richard I. Hanberry
A1 Anne Z. Murphy
YR 2020
UL http://biorxiv.org/content/early/2020/06/17/2020.06.16.154740.abstract
AB The present study investigated the impact of advanced age on morphine modulation of persistent inflammatory pain in male and female rats. The impact of age, sex, and pain on μ-opioid receptor (MOR) expression and binding in the ventrolateral PAG (vlPAG) was also examined using immunohistochemistry and receptor autoradiography. Intraplantar administration of Complete Freund’s adjuvant induced comparable levels of edema and hyperalgesia in adult (2-3mos) and aged (16-18mos) male and female rats. Morphine potency was highest in adult males, with a two-fold decrease in morphine EC50 observed in aged versus adult males (10.22mg/kg versus 5.19mg/kg). Adult and aged female rats also exhibited significantly higher EC50 values (10.69 mg/kg and 9.00 mg/kg, respectively) compared to adult males. The upward shift in EC50 from adult to aged males was paralleled by a reduction in vlPAG MOR expression and binding. The observed age-related reductions in morphine potency and vlPAG MOR expression and binding have significant implications in pain management in the aged population.Competing Interest StatementThe authors have declared no competing interest.