DIFFERENTIAL DISTRIBUTION OF NEUROPEPTIDE-Y Y1 AND Y2 RECEPTORS IN RAT AND GUINEA-PIG BRAINS

The distribution of neuropeptide Y Y1 and Y2 receptors has been extens ively studied in the rat using selective masking of[I-125]peptide YY b inding by Y1- and Y2-selective peptides. In the present study, we char acterized the binding of the subtype-selective radioligands [I-125](Le u(31)-Pro(34))-peptide YY and [I-125]peptide YY3-36 to rat and guinea- pig brains and identified differences in Y1 and Y2 distribution. [I-12 5](Leu(31)Pro(34))-peptide YY and [I-125]peptide YY3-36 bound to singl e sites in rat and guinea-pig brains with pharmacologies consistent wi th the Y1 and Y2 receptors, respectively. Autoradiographic studies wer e conducted using adjacent sections from rat and guinea-pig brains. Co mpared to the rat, the distribution of both Y1 and Y2 receptors was ma rkedly different in the guinea-pig. For example, a high level of Y1 bi nding was detected within the thalamus of the rat while, in the guinea -pig, very little Y1 binding was observed in this region. Y1 binding w as very low in the rat hippocampus, while the guinea-pig hippocampus c ontained high levels of Y1 binding. High levels of both Y1 and Y2 bind ing were observed in the guinea-pig cerebellum while, in the rat, only low levels of Y2 binding were visible. Therefore, the guinea-pig brai n exhibits dramatic differences in the pattern of Y1 and Y2 receptors when compared to the rat. It is likely that Y1 and Y2 receptors perfor m different roles in the central nervous system of guinea-pigs and rat s. Copyright (C) 1996 IBRO.