The effects of prostaglandin synthetase inhibitor indomethacin on the hypothalamic and neurohypophysial oxytocin content in euhydrated and dehydrated male white rats.

Rats euhydrated or dehydrated up to eight days were given intraperitoneally indomethacin (IM) twice daily in a dose of 0.2 mg/100 g of initial body weight. A single dose of IM injected to euhydrated animals did not affect the neurohypophysial oxytocic activity but decreased that potency in the hypothalamus. When IM was administered repeatedly during four or eight days, the hypothalamic oxytocic activity did not differ from the respective controls; under such conditions the oxytocic activity in the neurohypophysis increased progressively. Under conditions of dehydration the known depletion of hypothalamic and neurohypophysial oxytocin storage was not affected by indomethacin. It is therefore suggested that impulses of osmoreceptor origin are of distinct importance in determining the function of oxytocinergic neurones under conditions of inhibited prostaglandin synthesis.