Functional activation of cerebral glucose uptake after carotid body stimulation.

Abstract

Our laboratory is interested in the mechanism of glucose homeostasis (AlvarezBuylla & Roces de Alvarez-Buylla, 1975) and in particular in how appropriate levels of glucose are ensured for brain metabolism. The central nervous system (CNS) relies on a large and sustained supply of glucose for its functional activity (Erecinska & Silver, 1989; Ueki et al, 1988). However, the mechanisms that regulate the transfer of glucose from blood to brain are not well understood. Insulin increases membrane transfer of glucose in many tissues, but it does not regulate glucose uptake by the brain (LeMay et al, 1988). Besides its neuroendocrine function, the hypothalamus has an important role in integrating the activity of the autonomic nervous system (Chen et al, 1994), but its possible participation in regulating brain glucose uptake is unknown. In a previous study we have shown that changes in blood glucose concentration in the carotid body modify brain glucose retention (Alvarez-Buylla & Roces de Alvarez-Buylla, 1994). The role of the cerebrospinal fluid (CSF) in neuroendocrine functions, and as a conduit of communication between hypothalamus, pituitary and brain has been established (Jackson, 1984). In this paper we show that after carotid body receptor (CBR) stimulation a putative bioactive substance appears in the CSF that increases glucose retention in the brain. We further study the pituitary and adrenal glands participation in this reflex effect caused by CBR stimulation.