A functional role for vasoactive intestinal polypeptide in anterior cingulate cortex

Abstract

Vasoactive intestinal polypeptide (VIP) is present in high concentrations in the cerebral cortex, where it is the putative neurotransmitter of a major intracortical neuronal system^1–3. Homogenates of cortical tissue contain high-affinity, specific binding sites for VIP⁴ as well as an adenylate cyclase system which is sensitive to this peptide^5,6. As with many of the other peptidergic systems which have been identified in the central nervous system (CNS), it has proved extremely difficult to elucidate the nature and extent of the functional role of VIP in specific brain areas. Here, using the quantitative autoradiographic ¹⁴C-deoxyglucose technique in rats⁷ to provide insight into functional processes⁸, we describe the increases in glucose utilization which occur locally in anterior cingulate cortex following the unilateral injection of VIP (20 pmol) into this key brain area and, additionally, the focal alterations in glucose use in CNS regions having known neuronal connections with the injected region (for example, ipsilateral mediodorsal thalamus, ventral tegmental area, nucleus accumbens, caudate nucleus and contralateral cingulate cortex). These data provide evidence that VIP may modify the processing of afferent and efferent information within the anterior cingulate cortex in the conscious rat.