Melatonin membrane receptors MT1 and MT2 are expressed in ram spermatozoa from non-seasonal breeds

Sperm Behavior and Response to Melatonin under Capacitating Conditions in Three Sheep Breeds Subject to the Equatorial Photoperiod

“…Our group has previously shown that melatonin can regulate in vitro capacitation mainly via the MT 2 receptor in sperm from temperate-located rams [ 27 ]. In a previous study [ 34 ], we demonstrated that both melatonin receptors, MT 1 and MT 2 , are also present in the spermatozoa of these three Colombian breeds raised under equatorial photoperiodic conditions. In the present study, the effect of melatonin was, in general, more evident in the rainy season than in the dry season for all breeds.…”

“…This effect has been previously reported in somatic cells, where the exposure to a high level of melatonin can desensitize melatonin receptors [ 52 ]. Differences between breeds could also be attributed to previously described differences in the density of melatonin receptors [ 34 ]. The lesser effect of melatonin on sperm capacitation in Creole rams could be due to a lower MT 2 density in spermatozoa from this breed than the other two, as we described in a previous study [ 34 ].…”

“…Differences between breeds could also be attributed to previously described differences in the density of melatonin receptors [ 34 ]. The lesser effect of melatonin on sperm capacitation in Creole rams could be due to a lower MT 2 density in spermatozoa from this breed than the other two, as we described in a previous study [ 34 ]. Colombian Creole sheep are a native breed that, after five centuries of breeding in a 12L:12D photoperiod, are much more adapted to the equatorial climate and photoperiod than the Hampshire and Romney Marsh breeds, which were introduced into the country only 50 years ago.…”

“…In a previous study with these three Colombian breeds under equatorial photoperiod conditions, we observed differences in the melatonin concentration in seminal plasma obtained in the rainy and dry seasons [ 33 , 34 ]. As there was no change in night length that would modify the nocturnal secretion of melatonin, we hypothesized that these differences between seasons could be attributed to the content of phytomelatonin in the pasture [ 33 ].…”

“…As there was no change in night length that would modify the nocturnal secretion of melatonin, we hypothesized that these differences between seasons could be attributed to the content of phytomelatonin in the pasture [ 33 ]. Moreover, our group also demonstrated that spermatozoa from these Colombian rams also contain MT 1 and MT 2 receptors, and there are differences between breeds and seasons in the locations and densities of these receptors [ 34 ]. However, no previous studies have investigated how spermatozoa from these breeds, located in equatorial latitudes, respond under in vitro capacitating conditions, and whether exogenous melatonin could modulate this process.…”