Illustration of activated GABAergic neurons in the rostral part of the zona incerta and lateral hypothalamic area after paradoxical sleep hypersomnia.

Low power photomicrographs illustrating Fos-ir and GAD₆₇ mRNA labeled neurons in the rostral part of the zona incerta (A1) and the lateral hypothalamic area (B1) from a PSR rat. Numerous Fos-ir (brown nuclear staining) and GAD⁺ neurons (blue diffuse cytoplasmic staining) are observed in the rZI (A2), and the LHA (B2) and (B3) at high magnification. A large part of these neurons are double-labeled. B4 is an enlargement of B3 showing Fos-ir/GAD⁺ cells (black stars) surrounded by Fos-negative/GAD⁺ cells. In agreement with previous descriptions [14], a large number of GAD₆₇ mRNA labeled neurons (black) are distributed in zona incerta, the anterior and dorsomedial hypothalamic nuclei, the perifornical nucleus and the arcuate nucleus (A1, B1). A large but with a lesser density, number of GAD₆₇ cells was found in the dorsal and lateral hypothalamic areas (B1). No labeling was observed in the ventromedial nucleus of the hypothalamus (B1). Abbreviations: 3V: 3^rd ventricle; f: fornix; aLH: lateral hypothalamic area, anterior part; mt: mammillothalamic tract; opt: optic tract; Rt: reticular nucleus of the thalamus; rZI: zona incerta, rostral part; SubI: subincertal nucleus; tLH: lateral hypothalamic area, tuberal part; VMH: ventromedial hypothalamic nucleus; ZID: zona incerta, dorsal part; ZIV: zona incerta, ventral part. Scale bars, 500µm for A1 and B1; 50µm for A2, B2 and B3 and 25µm for B4.