Figure 1

H ₃ receptor mRNA expression and binding in euthermic and hibernating ground squirrel brains. Coronal sections of ground squirrel brains showing H₃ receptor expression revealed by in situ hybridization using [³⁵S]-labeled oligonucleotide probe complementary to H₃ mRNA (A-F) and [³H]NAMH binding to histamine H₃ receptors (G-L). The H₃ mRNA expression is higher in the cortex, caudatus and putamen but not in the globus pallidus and substantia nigra during hibernation (B and E) than during interbout euthermia (A and D). The signal was blocked with excess cold H₃ oligonucleotide probe (C and F). [³H]NAMH binding to histamine H₃ receptors is higher in the cortex, globus pallidus and substantia nigra during hibernation (H and K) compared to interbout euthermic brains (G and J). The specific H₃ receptor antagonist clobenpropit completely blocked the [³H]NAMH binding (I and L).