Characterization and autoradiographic distribution of vasoactive intestinal peptide binding sites in the rat central...

Biochemical characteristics and topographical distribution of mono-[125I )vasoactive intestinal peptide (VIP) binding sites in rat brain were studied on tissue sections and by quantitative autoradiography. Biochemical investigations show two classes of binding sites with a dissociation constant of 1.03 +/- 0.11 nM and 68 +/- 14 nM and a maximal binding capacity of 43.3 +/- 5.1 fmol/mg protein and 713 +/- 117 fmol/mg protein respectively. The order of potency of various peptides to inhibit 125I-VIP binding to brain sections is: VIP greater than PHI greater than secretin greater than VIP greater than hGRF. Autoradiography reveals the highest densities of binding sites in the pineal gland, the dentate gyrus of the hippocampus, the central amygdaloid nucleus and in various thalamic nuclei such as the mediodorsal, lateral posterior, submedius, dorsolateral and medial geniculate nuclei. Similar high densities are observed in the olfactory bulbs as well as in the suprachiasmatic and dorsomedial nuclei of the hypothalamus and in the superior colliculus. These data together with the distribution of the endogenous peptide suggest a physiological role for VIP both in the regulation of CNS activities and pituitary functions.