We have developed a mouse model in which a specific population of inhibitory neurons can be selectively ablated by the action of diphtheria toxin (DT). The model involves targeting the human DT receptor to the agouti-related protein (Agrp) locus so that systemic administration of DT kills all of the AgRP-expressing neurons, resulting in starvation of the mice. Ablation of AgRP neurons results i...

Deficient leptin signaling causes infertility via reduced activity of GnRH neurons, causing a hypogonadal state in both rodents and humans. Because GnRH neurons do not express leptin receptors, leptin's effect on GnRH neurons must be indirect. Neurons within the hypothalamic arcuate nucleus that coexpress AGRP and NPY are considered to be important intermediate neurons involved in leptin regula...

Melanocortin- 4 receptor (MC4R) and agouti- related peptide (AgRP) are involved in energy homeostasis in rats. According to MC4R and AgRP effects on luteinizing hormone (LH) secretion, they may influence the estrous cycle of rats. Therefore, the aim of this study was to investigate the expression of MC4R and AgRP mRNAs at different stages of estrous cycle in the rat’s hypothalamus. The estrous ...

During lactation, the levels of neuropeptide Y (NPY), which plays an important role in mediating food intake, are significantly elevated in a number of hypothalamic areas, including the arcuate nucleus (ARH). To identify additional hypothalamic systems that might be important in mediating the increase in food intake and alterations in energy homeostasis during lactation, the present studies exa...

Teubner BJ, Keen-Rhinehart E, Bartness TJ. Third ventricular coinjection of subthreshold doses of NPY and AgRP stimulate food hoarding and intake and neural activation. Am J Physiol Regul Integr Comp Physiol 302: R37–R48, 2012. First published October 19, 2011; doi:10.1152/ajpregu.00475.2011.—We previously demonstrated that 3rd ventricular (3V) neuropeptide Y (NPY) or agouti-related protein (Ag...

Although excess hypothalamic agouti-related peptide (AGRP), an endogenous antagonist of the melanocortin 3/4 receptor, causes hyperphagia and obesity, its role in regulating cardiovascular function is unclear. This study examined control of mean arterial pressure (MAP), heart rate (HR), and metabolism during chronic central administration of AGRP in rats. A cannula was placed in the lateral ven...

The central melanocortin (MC) system has been demonstrated to act downstream of leptin in the regulation of body weight. The system comprises alpha-MSH, which acts as agonist, and agouti-related protein (AgRP), which acts as antagonist at the MC3 and MC4 receptors (MC3R and MC4R). This property suggests that MCR activity is tightly regulated and that opposing signals are integrated at the recep...

The melanocortin 4 receptor (MC4R) is a G-protein coupled receptor mainly expressed in the central nervous system of vertebrates. Activation of the MC4R leads to a decrease in food intake, while inactivating mutations are a genetic cause of obesity. The binding of agoutirelated protein (AGRP) reduces agonist-stimulated cAMP production (competitive antagonist) but also the basal activity of the ...