Effects of Light at Night and Methamphetamine on Reproductive Hormones, Estrous Cycle and Histology of the Reproductive Organs in Female Albino Wistar Rats
Makuachukwu Francisca Chinweokwu Mgbemena *
Department of Physiology, Faculty of Basic Medical Sciences, College of Health Sciences, Nnamdi Azikiwe University, Nnewi Campus, Nigeria.
Ed. Nwobodo
Department of Physiology, Faculty of Basic Medical Sciences, College of Health Sciences, Nnamdi Azikiwe University, Nnewi Campus, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Background and Aim: Light at night (LAN) and methamphetamine (Meth) are emerging environmental and pharmacological stressors implicated in neuroendocrine and reproductive dysfunction. This study investigated the independent and combined effects of LAN and Meth on reproductive hormone profiles, cortisol levels, estrous cyclicity and histological integrity of the ovaries and uterus in female Albino Wistar rats.
Methodology: Twenty-four adult female Albino Wistar rats (120–150 g) were randomly assigned into four groups of six (n = 6). Group A (control) received normal saline under a standard 12:12-hour light-dark cycle. Group B (LAN) was exposed to 24-hour continuous light for 28 days. Group C (Meth) received methamphetamine at 5mg/kgbw orally for 28 days under standard light-dark conditions. Group D (LAN + Meth) received both exposures simultaneously. Serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), estrogen, progesterone, and cortisol were measured using ELISA. Estrous cycles were monitored through vaginal smear cytology. Ovarian and uterine tissues were weighed and examined histologically. Data were analyzed using one-way ANOVA with post hoc LSD at p ≤ 0.05.
Results: Significant reductions in LH were observed in all treated groups compared to control (F= 8.039, p ≤ 0.05). FSH levels decreased significantly in Groups B and C, while Group D showed a significant increase compared to Group C (p ≤ 0.05). Estrogen levels were significantly elevated in the LAN group, whereas progesterone changes were not significant. Serum cortisol was significantly suppressed in all treated groups, with the greatest reduction in Meth-exposed rats. Estrous cycles showed progressive irregularity in all treated groups. Histology revealed mild degenerative and inflammatory changes, most notable in the LAN group, with largely preserved architecture overall.
Conclusion: LAN and Meth disrupt hypothalamic–pituitary–gonadal axis function and stress hormone regulation, with LAN producing more pronounced endocrine and histological alterations.
Keywords: Light-at-night, methamphetamine, circadian disruption, female fertility, HPG axis, estrous cycle