Figure 1.

Distributions of orexin immunoreactive neurons. A, The orexin field in a wild-type (WT) mouse injected with AAV-mCherry shows the normal, moderately dense cluster of orexin-immunoreactive (IR) neurons above the fornix (f) and in the lateral hypothalamus (LH). B, An Atx mouse injected with AAV-mCherry has a few scattered orexin-IR neurons in this region, but the cells are small and weakly IR and axonal labeling is nearly absent. C and D, An AAV-orexin injection site in an Atx mouse shows many neurons expressing orexin in the posterior hypothalamus (PH), dorsomedial nucleus of the hypothalamus (DMH), tuberomammillary nucleus (TMN), and other parts of the mammillary region. Axons from these neurons course around the mammillothalamic tract (mt) and densely innervate the amygdalohippocampal area (AHiA) plus other sites. AAV, adeno-associated viral vector; Atx, transgenic (ataxin); opt, optic tract; ic, internal capsule; 3V, third ventricle; cp, cerebral peduncle.