Species differences in the expression and distribution of the neuropeptide Y Y1, Y2, Y4, and Y5 receptors in rodents,guinea pig,and primates brains

The respective distribution of neuropeptide Y Y₁, Y₂, Y₄, and Y₅ receptor subtypes was investigated in rodents (rat and mouse), guinea pig, and primates (marmoset and vervet monkeys and human) brains, representing three orders of mammals. [¹²⁵I][Leu³¹,Pro³⁴]PYY (total Y₁-like; Y₁, Y₄, and Y₅) and [¹²⁵I]PYY_3–36 (total Y₂-like; Y₂ and possibly Y₅) binding sites were discretely but similarly distributed in the rat and mouse brain, each having its unique pattern. In contrast, surprisingly low levels of [¹²⁵I]PYY_3–36 binding sites were found in the guinea pig brain including in the hippocampal formation. [¹²⁵I][Leu³¹,Pro³⁴]PYY/BIBP3226-insensitive binding sites (Y₅-like) were found in different areas of the rat and guinea pig brains. The primate brains also revealed a different distribution binding profile for these various NPY receptor subtypes. Although the human and vervet brains contained very low amounts of [¹²⁵I][Leu³¹,Pro³⁴]PYY sites (Y₁-like) in most brain regions, except for the dentate gyrus of the hippocampus, the marmoset brain contains significant amounts of both [¹²⁵I][Leu³¹,Pro³⁴]PYY (Y₁-like) and [¹²⁵I]PYY_3–36 (Y₂-like) binding sites. Additionally, [¹²⁵I][Leu³¹,Pro³⁴]PYY/BIBP3226-insensitive binding sites were not clearly detected in the vervet and human brains. On the other hand, Y₅-like binding sites were observed in few regions of the marmoset brain. Finally, [¹²⁵I]hPP (Y₄/Y₅-like) were very discretely distributed in the rat brain, being concentrated in the paraventricular nucleus of the hypothalamus and the interpeduncular nucleus. The marmoset brain is apparently not enriched with specific [¹²⁵I]hPP sites. Taken together, these data show that significant species differences exist in the level of expression and distribution of various NPY receptor subtypes in the mammalian brain. J. Comp. Neurol. 402:372–384, 1998. © 1998 Wiley-Liss, Inc.