The expression of prepro-orexin (PPO) mRNA in the rat brain was investigate
d by in situ hybridization histochemistry. In the lateral and posterior hyp
othalamic areas, which are considered to produce exclusively PPO mRNA, we f
ound high levels of PPO mRNA expressions. We also localized PPO mRNA hybrid
ization signals at lower levels around the lateral ventricles, the third an
d fourth ventricle. Cellular analysis by emulsion autoradiography revealed
the expression of PPO mRNA in the ependymal cell layer. Our results demonst
rate that beside the lateral and posterior hypothalamus PPO mRNA is express
ed in ependymal cells. NeuroReport 12:2117-2120 (C) 2001 Lippincott William
s & Wilkins.