Functional role for vasoactive intestinal polypeptide in the caudate nucleus: a 2-deoxy[14C]glucose investigation

The quantitative autoradiographic 2-deoxy-[14C]glucose technique has been used with conscious rats to investigate the functional consequences (reflected as alterations in local rates of glucose utilization) of unilateral intrastriatal administration of vasoactive intestinal polypeptide. Intrastriatal administration of vasoactive intestinal polypeptide (20 pmol) significantly increased local glucose utilization in the injected striatum, where the increased use was localized in small punctate areas (100-500 microns wide in coronal sections) scattered throughout the nucleus at considerable distances (up to 4 mm) from the injection site. Significantly increased glucose utilization after intrastriatal injection of vasoactive intestinal polypeptide was observed in a number of regions (e.g., substantia nigra pars compacta, entopeduncular nucleus, lateral habenular nucleus, entorhinal, pyriform cortices, and amygdala) with known primary or secondary neuronal connections with the caudate nucleus. These alterations in glucose utilization were highly focal in nature, with the majority (40 of the 50 examined) of brain regions displaying unaltered rates of glucose utilization. The data provide evidence, obtained in conscious animals, that vasoactive intestinal polypeptide can modify functional processes in the caudate nucleus.