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Insulin acts in the brain to suppress feeding, whereas neuropeptide Y (NPY) has the opposite effect. Since fasting lowers plasma insulin levels and increases hypothalamic synthesis of NPY, we proposed that insulin may inhibit hypothalamic NPY gene expression. To test this hypothesis, we used RIA and in situ hybridization histochemistry to determine if(More)
Extensive historical evidence from the drug abuse literature has provided support for the concept that there is functional communication between central nervous system (CNS) circuitries which subserve reward/motivation, and the regulation of energy homeostasis. This concept is substantiated by recent studies that map anatomical pathways, or which(More)
The hormones insulin, leptin, and ghrelin have been demonstrated to act in the central nervous system (CNS) as regulators of energy homeostasis, acting at medial hypothalamic sites. Here, we summarize research demonstrating that, in addition to direct homeostatic actions at the hypothalamus, CNS circuitry that subserves reward and is also a direct and(More)
IRS-1 is phosphorylated on tyrosine residues after insulin stimulation and participates in the early events of signal transduction in peripheral insulin-sensitive tissues. This study determined whether neuronal populations in the rat olfactory bulb and hippocampus (brain regions which have very high concentrations of insulin receptors) also express IRS-1(More)
The authors hypothesized that insulin and leptin, hormones that convey metabolic and energy balance status to the central nervous system (CNS), decrease the reward value of food, as assessed by conditioned place preference (CPP). CPP to high-fat diet was blocked in ad-lib fed rats given intraventricular insulin or leptin throughout training and test or(More)
The effect of caloric deprivation to stimulate hypothalamic neuropeptide Y (NPY) gene expression is hypothesized to represent a physiologically important adaptation in body weight homeostasis. To evaluate the specificity of this response, we used in situ hybridization histochemistry to measure hypothalamic expression of mRNA encoding NPY, galanin, and the(More)
Rats and humans avidly consume flavored foods that contain sucrose and fat, presumably due to their rewarding qualities. In this study, we hypothesized that the complex mixture of corn oil, sucrose, and flavor is more reinforcing than any of these components alone. We observed a concentration-dependent increase in reinforcers of sucrose solutions received(More)
In peripheral insulin-sensitive tissues, insulin receptor substrate (IRS-1) undergoes tyrosine phosphorylation immediately after cells are stimulated by insulin or insulin-like growth factor-1 (IGF-1), and may function as a molecular link between insulin/IGF-1 receptor tyrosine kinases and enzymes regulating cell growth and metabolism. A fundamental(More)
The hormone insulin acts in the central nervous system (CNS) as a regulator of body adiposity and food intake. Recent work from our laboratory has provided evidence that one way by which insulin may decrease food intake is by decreasing the rewarding properties of food. Evidence from others suggests that endogenous opioids may mediate the palatable(More)
Findings from our laboratory and others have demonstrated that the hormone insulin has chronic effects within the CNS to regulate energy homeostasis and to decrease brain reward function. In this study, we compared the acute action of insulin to decrease intake of a palatable food in two different behavioral tasks-progressive ratios sucrose(More)