Structural reorganization in the supraoptic nucleus of withdrawn rats following long-term alcohol consumption

We have recently shown in the supraoptic nucleus (SON) of the rat that prolonged ethanol consumption induces cell degeneration and enlargement of the surviving neurons and of their subcellular organelles. We analyzed the SON of withdrawn rats to evaluate whether it displays any evidence of morphological reorganization following abstinence from ethanol, inasmuch as in this condition the ethanol-induced changes in the plasma levels of neurohormones and plasma osmolality are no longer detectable. A group of 18-month-old withdrawn rats was compared with age-matched, pair-fed control and ethanol-treated rats. To differentiate between the effects of withdrawal and the effects of rehydration, a group of 18-month-old rehydrated rats was also included in this study and compared with age-matched, pair-fed control and dehydrated rats. We estimated the volume of SON, and the total number and mean volume of its neurons. The cross-sectional areas of the vasopressinergic and oxytocinergic populations were also evaluated. At the ultrastructural level, we determined the volumes and surface areas of the rough endoplasmic reticulum and Golgi apparatus, and the volumes of neurosecretory granules and nucleoli. In withdrawn animals, the total number of SON neurons was smaller than in controls, although the neuronal volume was greater. The number of SON neurons did not differ between withdrawn and ethanol-treated rats, despite the reduced volume of SON in the former animals. The decrease of SON volume correlated with and was caused by a reduction in the volume of SON neurons and in the size of the organelles involved in neuro-hormone synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)