Overview of orexin 2 receptors (OX-2R; red) and cannabinoid receptor 1 (CB1R; green) immunoreactivity in the whole adult zebrafish brain. (A?E) Schematic drawings of five coronal sections of the adult zebrafish brain showing, at right, the distribution of OX-2R/CB1R co-expression (yellow solid circles) and, at left, the brain nuclei and regions according to Wullimann et al. (1996). (A₁?E₁) Photomicrographs of the sections corresponding to the schematic coronal sections reported in (A?E). (A,A₁) Telencephalon: OX-2R/CB1R co-localization in lateral (Dl), medial (Dm), central (Dc) and posterior (Dp) part of the dorsal telencephalon and in the dorsal (Vd) and lateral (Vl) part of the ventral telencephalon. (B,B₁) Diencephalon: OX-2R/CB1R co-localization in ventral habenular nucleus (Hav), optic tectum (TeO), ventral zone of the periventricular hypothalamus (Hv). (C,C₁) Dienchephalon/mesencephalon: OX-2R/CB1R co-localization in the torus longitudinalis (TL), medial (PGm) and lateral (PGl) preglomerular nuclei, lateral hypotalamus (LH), Hv, and anterior (ATN) and posterior (PTN) tuberal nuclei. (D,D₁) Mesencephalon: OX-2R/CB1R co-localization in TL, caudal (Hc) and dorsal (Hd) zone of the periventricular hypothalamus, torus lateralis (Tla), central nucleus of inferior lobe (CIL) and diffuse nucleus of inferior lobe (DIL). (E,E₁) Rhombencephalon: OX-2R/CB1R co-localization in TeO, octaval nerve (VIII), intermediate reticular formation (IMRF) and tractus tectobulbaris (TTB). AON, anterior octaval nucleus; Cantd, commissura anterior, pars dorsalis; Cce, corpus cerebelli; Chor, Commissura horizontalis; CM, corpus mammillaris; CP, central posterior thalamic nucleus; CPN, central pretectal nucelus; Cpop, commissura postoptica; DAO, dorsal accessory optic nucleus; DiV, Diencephalic ventricle; DOT, dorsomedial optic tract; DP, dorsal posterior thalamic nucleus; DTN, dorsal tegmental nucleus; EG, eminentia granularis; End, entopeduncular nucleus, dorsal part; FR, fasciculus retroflexus; I, intermediate thalamic nucleus; Lca, lobus caudalis cerebelli; LFB, lateral forebrain bundle; LLF, lateral longitudinal fascicle; LOT, lateral olfactory tract; MFB, medial forebrain bundle; MLF, medial longitudinal fascicle; MON, medial octavolateralis nucleus; MOT, medial olfactory tract; PGZ, Periventricular gray zone of the optic tectum; Pit, pituitary; PPd, periventricular pretectal nucleus, dorsal part; PPp, parvocellular preoptic nucleus, posterior part; PPv, periventricular pretectal nucleus, ventral part; PSm, magnocellular superficial pretectal nucleus; PSp, parvocellular superficial pretectal nucleus; SC, suprachiasmatic nucleus; SGT, secondary gustatory tract; TelV, telencephalic ventricle; TeV, Tectal ventricle; TPM, tractus pretectomammillaris; TPp, periventricular nucleus of posterior tuberculum; TS, torus semicircularis; Val, lateral division of valvula cerebelli; VL, Ventrolateral thalamic nucleus; VM, Ventromedial thalamic nucleus; VOT, ventral optic tract; Vv, ventral nucleus of ventral telencephalic area. Scale bar, 250 ?m.

Distribution of OX-2R (red) and CB1R (green), and their co-localization OX-2R/CB1R (yellow) in coronal sections of the telencephalon. (A?C) OX-2R/CB1R co-expression has been observed in the dorsal and ventral telencephalon of zebrafish brain. (A₁) Higher magnification of the field boxed in (A) showing the OX-2R/CB1R co-expression within the dorsal nucleus of the ventral telencephalon (Vd). (B₁,B₂) Higher magnification of the fields boxed in (B) showing the OX-2R/CB1R co-expression within the dorsal (Dd) (B₁) and medial (Dm) (B₂) part of the dorsal telencephalon. (C₁) Higher magnification of the field boxed in (C) showing the OX-2R/CB1R co-expression within the parvocellular preoptic nucleus, anterior part (Ppa). DAPI (Blue) was used as a counterstaining to show nuclei. Dc, central part of the dorsal telencephalon; Dp, posterior part of the dorsal telencephalon; NT, nucleus taeniae. Scale bar, 250 ?m for (A?C); 50 ?m for (A₁,B₁,B₂,C₁).

Distribution of OX-2R (red) and CB1R (green), and their co-localization OX-2R/CB1R (yellow) in coronal sections of the diencephalon. (A,B) OX-2R/CB1R co-expression has been observed in the suprachiasmatic nucleus (SC), ventrolateral (VL) and ventromedial (VM) thalamic nuclei, dorsal habenular nucleus (Had), optic tectum (TeO), periventricular gray zone of the optic tectum (PGZ), ventral optic tract (VOT), lateral forebrain bundle (LFB) and ventral zone of the periventricular hypothalamus (Hv). (A₁?A₃) Higher magnification of the fields boxed in (A) showing the OX-2R/CB1R co-expression within the Had, VL, VM (A₁), SC (A₂) and TeO (A₃). (B₁?B₃) Higher magnification of the fields boxed in (B) showing the OX-2R/CB1R co-expression within the TeO, PGZ (B₁), VOT (B₂), LFB and Hv (B₃). DAPI (Blue) was used as a counterstaining to show nuclei. Scale bar, 250 ?m for (A,B); 50 ?m for (A₁?A₃,B₁?B₃).

Distribution of OX-2R (red) and CB1R (green), and their co-localization OX-2R/CB1R (yellow) in coronal sections of the diencephalon/midbrain. (A?C) OX-2R/CB1R co-expression has been observed in the lateral (PGl) and medial (PGm) preglomerular nuclei, VOT, central posterior thalamic nucleus (CP), posterior tuberal nucleus (PTN), lateral hypothalamus (LH), ventral zone of the periventricular hypothalamus (Hv), periventricular gray zone of the optic tectum (PGZ), optic tectum (TeO), dorsal zone (Hd) of the periventricular hypothalamus, torus lateralis (Tla), diffuse nucleus of inferior lobe (DIL). (A₁) Higher magnification of the field boxed in (A) showing the OX-2R/CB1R co-expression within the PGl and PGm. (B₁?B₄) Higher magnification of the fields boxed in (B) showing the OX-2R/CB1R co-expression within the CP and VOT (B₁), PTN, LH and Hv (B₂), PGl and PGm (B₃), TeO and PGZ (B₄). (C₁?C₃) Higher magnification of the fields boxed in (C) showing the OX-2R/CB1R co-expression within the LH (C₁), Hd, Tla and DIL (C₂), TeO (C₃). (D) Detail of OX-2R/CB1R co-expression in LH: arrow showing a putative adjacent localization of OX-2R/CB1R and arrowhead showing a putative co-localization and overlapping of OX-2R/CB1R in the same cells. DAPI (Blue) was used as a counterstaining to show nuclei. Scale bar, 250 ?m for (A?C); 50 ?m for (A₁,B₁?B₄,C₁?C₃); 25 ?m for (D).

Distribution of OX-2R (red) and CB1R (green), and their co-localization OX-2R/CB1R (yellow) in coronal sections of diencephalon/mesencephalon. (A,B) OX-2R/CB1R co-expression has been observed in the dorsal (Hd) and central (Hc) zone of the periventricular hypothalamus, DIL and TTB. (A₁) Higher magnification of the field boxed in (A) showing the OX-2R/CB1R co-expression within the Hc, Hd and DIL. (B₁?B₃) Higher magnification of the fields boxed in (B) showing the OX-2R/CB1R co-expression within the TTB (B₁), Hd and DIL (B₂), Hc (B₃). DAPI (Blue) was used as a counterstaining to show nuclei. Scale bar, 250 ?m for (A,B); 50 ?m for (A₁,B₁?B₃).

Distribution of OX-2R (red) and CB1R (green), and their co-localization OX-2R/CB1R (yellow) in coronal sections of the midbrain. (A,B) OX-2R/CB1R co-expression has been observed in the optic tectum (TeO), along the tectal ventricle (TeV), TTB, dorsal (Hd) and central (Hc) zone of the periventricular hypothalamus, DIL. (A₁?A₅) Higher magnification of the fields boxed in (A) showing the OX-2R/CB1R co-expression within the TeO (A₁), TeV (A₂), TTB (A₃), Hd (A₄), Hc (A₅). (B₁) Higher magnification of the field boxed in (B) showing the OX-2R/CB1R co-expression within the DIL. DAPI (Blue) was used as a counterstaining to show nuclei. Va, Valvula Cerebelli. Scale bar, 250 ?m for (A,B); 50 ?m for (A₁?A₅,B₁).

Distribution of OX-2R (red) and CB1R (green), and their co-localization OX-2R/CB1R (yellow) in coronal sections of the rhombencephalon. (A,B) OX-2R/CB1R co-expression has been observed in the IMRF and octaval nerve (VIII). (A₁,B₁) Higher magnification of the fields boxed in (A,B) showing the OX-2R/CB1R co-expression in the VIII. DAPI (Blue) was used as a counterstaining to show nuclei. Cce, corpus cerebelli. Scale bar, 250 ?m for (A,B); 50 ?m for (A₁,B₁).