Effects of different light regimes on prolactin concentration in rat

  • S Mohammadzadeh
  • A Kiani
  • N Lorzadeh
  • A Mohammadi
  • E Rafii


Prolactin is a peptide hormone which is secreted from hypophysis. Prolactin
concentration differs in male and female. Even though prolactin has  lactotpope effect, it has disturbances effects on pulsatory secretion of gonadotropins as well as on ovulation. In spite of different plasma level of prolactin in different seasons, the effects of light regime on prolactin secretion still is unclear. Eighty Wistar rats were selected and divided
into four groups. Each treatment was exposed in different photoperiod; natural light (control NL), 24 hours light (permanent light LL), 24 hours darkness (permanent darkness DD), and 12 hours light-12 hours darkness (light-dark LD). Blood samples from the heart were taken every 3 month during year. Prolactin concentration was determined using RIA. Data were analyzed using ANOVA and means were compared using Duncan multiple range test. Prolactin concentration in control (NL), dark (DD), light-dark (LD) and permanent light (LL) were 1.10, 1.00, 0.80 and 0.60 ng/ml, respectively. Light regime had a significant effect on prolactin concentration (p<0.05). Prolactin was significantly lower in permanent light than other treatments. Means of prolactin in permanent dark and light-dark weren’t differ with control (p>0.05). Permanent light will reduce the prolactin level. It seems to be one of the causes of short estrous cycles in permanent light is prolactin levels. These finding can be used as a model in human

Keywords: Photoperiods, Prolactin concentration, Lactogen, Mammotropin, Lactotropic hormone, Hypothalamus, Hypophysis, Metabolic performance, Rats


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eISSN: 1597-3115