[Pineal peptides in the regulation of milk-ejection reflex in lactating rats].

: The effects of pineal peptides (mol. mass 1-4 kDa) intranasal infusions on some parameters of milk-ejection reflex were investigated. Peptides were extracted from dairy-cattle pineal glands. Pineal peptides increase body weight, levels of water intake, plasma prolactin concentration and milk yield in rats when infusing daily in dose 1 microgram/kg from the third day of lactation. On 9th and 12th days of lactation during 1-hour nursing seance the significantly greater number of reflective milk ejections were found. When 1 hour before the peptides infusion rats were intraperitoneally injected by rabbit antiserum to oxytocin (200 microliters at dilution of 1:20) the effects of pineal peptides were significantly less expressive or were absent at all. Using enzymimmunoassay it was demonstrated that there were greater increasing of oxytocin content in pineal gland in suckling-induced oxytocin release from neurohypophysial system in the chronic pineal peptides-treated female rats compared with control. This effect was absent when rats were injected by oxytocin antibodies. These data suggest that pineal peptides can participate in forming of reflect oxytocin release pattern. This pattern is initiated by suckling and is limited by oxytocin content in blood.