Localization and expression of androgen receptor (AR) and melatonin membrane receptor (MT1R) in accessory sex organs of adult male golden hamster, Mesocricetus auratus: Modulation by photoperiod

Photoperiodic variation in localization and expression patterns of androgen (AR) and melatonin receptor (MT1R) on accessory sex organs (ASOs) are still unexplored for any seasonal breeder. In the present study, we assessed the AR and MT1R expression dynamics in ASOs of male golden hamster, Mesocricetus auratus exposed to different photoperiodic conditions i.e. critical- (CP; 12.5L : 11.5D); short-day- (SD; 8L : 16D) and long-day- (LD; 16L : 8D) photoperiod for 10 weeks. Under SD condition ASOs regressed and reduced drastically their structural integrity as evidenced from the gross-morphology, weight and histoarchitecture. Differential immunoreactivity for MT1R and AR in ASOs of M. auratus suggests a possible involvement of both the receptors in transducing the photoperiodic signals for modulation of ASOs function. Biochemical analyses of functional markers suggest the functionality of ASOs being suppressed when exposed to SD condition that might be due to a concomitant decrease in plasma testosterone level along with AR expression and an increase in plasma melatonin level and MT1R expression. An opposite response was observed in hamsters exposed to LD condition. It is evident that, experimental photoperiod regulated the functional integrity of ASOs as it does in nature via modulation of plasma level of melatonin and testosterone and expression patterns of their receptors. It also suggests the potency of photostimulation on ASOs besides its effect on testes. Thus, photoperiodic induction of ASOs function(s) may be used for improvement of quality and quantity of sperm of some endangered seasonally breeding mammals even during reproductive inactive phase.