F. Gauer et al., SEASONAL REGULATION OF MELATONIN RECEPTORS IN RODENT PARS TUBERALIS -CORRELATION WITH REPRODUCTIVE STATE, Journal of neural transmission, 96(3), 1994, pp. 187-195
Using quantitative autoradiography, we have studied the relationship b
etween melatonin receptor density in the pars tuberalis (PT) and photo
periodic changes in sexual activity in a photoperiodic (Syrian hamster
), and a non photoperiodic (rat) rodent. Syrian hamsters exposed to sh
ort photoperiod (SP) for 13 weeks or kept in long photoperiod (LP) wit
h daily melatonin injections for 8 weeks, had both gonadal regression
and a significant decrease in 2-I-125- melatonin binding site density
in the PT when compared to controls. In contrast, when the animals wer
e sexually active, photorefractory Syrian hamsters exposed to SP for 2
7 weeks, or rats kept for 13 weeks in SP, the PT melatonin receptor de
nsity was similar to that of control animals kept in LP. These results
show clearly that a correlation exists between gonadal status and den
sity of melatonin receptors in the PT and suggest that the PT could be
the site where melatonin mediates its effects on seasonal function.