[Effects of blinding by bilateral orbital enucleation on the ultrastructure of the pineal gland in the female garden dormouse (Eliomys quercinus L.). Correlations with the hypothalamo-pituitary-ovarian axis].

Dormice were blinded by bilateral enucleation in December before hibernation or in March at the end of hibernation and were then studied in July and October. All the animals stayed in permanent anoestrus even at long-term. The ultrastructure of the pinealocyte was very characteristic, presenting typical elements of both hibernal anoestrus and sexual activation. Two organelles were well developed in enucleated dormice: reticulo-endoplasmic vacuoles and liposomes whose development seemed to be associated with protein secretions and pineal serotonine level, respectively. The hypothalamo-hypophyseal characterististics of the enucleated animals were also surprising: the hypothalamic LHRH load was important and hypophyseal gonadotropic cell development normal although the ovaries were hypoactive. The dormouse has a seasonal sexual cycle which cannot be realized without light. Pineal ultrastructural findings correlated with the activity of the hypothalamo-pituitary-ovarian axis lead us to think that this endocrine gland plays a role in the action of light on sexual activity.