SAT-020 The Effects of Pre-Adolescent Morphine Exposure on Puberty Onset and Body Weight

Abstract Disclosure: E. Klindtworth: None. J. Bryant: None. B. Procaccini: None. Z. Khan: None. S.B. Stephens: None. Adolescence is a developmental period between 10 and 24 years old that causes behavioral, psychological, and emotional changes, causing an increased susceptibility to drug and alcohol usage. It is also a time of hormonal changes, including the onset of puberty. During adolescence, sex specific changes occur in neural development, including in response to opioids like morphine. These changes are most pronounced during the adolescent critical period when development and behavior are thought to be permanently altered. Previous studies have shown that morphine exposure during puberty can have lasting effects on behavior and hormone levels. This study aims to determine the effects of morphine exposure just prior to puberty (PND 23-27) on body weight and the timing of puberty onset. We hypothesized that morphine exposure prior to puberty would delay puberty onset in both sexes. Male and female adult Sprague Dawley Rats were obtained and bred. Litters were weaned on PND21 and pair-housed with open access to food and water. All rats (n=14-16/sex/treatment) were handled on PND 21 and PND 22 to acclimate them to injection procedures. Rats were subcutaneously injected with either Morphine Sulfate (3mg/kg-6mg/kg) or Sterile Saline, twice daily from PND 23-27, which is prior to puberty, as well as weighed once daily. Starting on PND 28, male and female rats were checked daily for puberty onset which was determined by Vaginal Opening (females) and Preputial Separation (males). Following Vaginal Opening, vaginal lavage was performed on females daily. We found no significant difference in age of vaginal opening (VO), first estrus, or preputial separation (PPS) between saline and morphine groups. Additionally, prepubertal body weight increased daily for both morphine and saline treated males and did not differ between treatment groups. Our study shows morphine exposure just prior to puberty did not have a significant impact on the age of vaginal opening or first estrus in females, and preputial separation in males, which does not support our hypothesis. Although the morphine treatment occurred prior to the presence of VO, first estrus, and PPS, it is possible that the cascade of events in the brain that triggers puberty onset was already started and thus, would not be affected by morphine exposure. Future studies should repeat the study during earlier age points as well as later ages (i.e. during puberty) to better understand how morphine interacts with the reproductive axis. Morphine exposure during this prepubertal time period may still have lasting effects on adult fertility and reproduction, despite having no effects on pubertal timing, and future studies are needed to determine the long-term consequences of adolescent morphine exposure. Presentation: Saturday, July 12, 2025