| 1. |
- Adage, Tiziana, et al.
(författare)
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Hypothalamic, metabolic, and behavioral responses to pharmacological inhibition of CNS melanocortin signaling in rats
- 2001
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Ingår i: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 21:10, s. 3639-3645
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Tidskriftsartikel (refereegranskat)abstract
- The CNS melanocortin (MC) system is implicated as a mediator of the central effects of leptin, and reduced activity of the CNS MC system promotes obesity in both rodents and humans. Because activation of CNS MC receptors has direct effects on autonomic outflow and metabolism, we hypothesized that food intake- independent mechanisms contribute to development of obesity induced by pharmacological blockade of MC receptors in the brain and that changes in hypothalamic neuropeptidergic systems known to regulate weight gain [i. e., corticotropin-releasing hormone (CRH), cocaine- amphetamine- related transcript (CART), proopiomelanocortin (POMC), and neuropeptide Y (NPY)] would trigger this effect. Relative to vehicle- treated controls, third intracerebroventricular (i3vt) administration of the MC receptor antagonist SHU9119 to rats for 11 d doubled food and water intake (toward the end of treatment) and increased body weight (similar to 14%) and fat content (similar to 90%), hepatic glycogen content (similar to 40%), and plasma levels of cholesterol (similar to 48%), insulin (similar to 259%), glucagon (similar to 80%), and leptin (similar to 490%), whereas spontaneous locomotor activity and body temperature were reduced. Pair- feeding of i3vt SHU9119- treated animals to i3vt vehicle- treated controls normalized plasma levels of insulin, glucagon, and hepatic glycogen content, but only partially reversed the elevations of plasma cholesterol (similar to 31%) and leptin (similar to 104%) and body fat content (similar to 27%). Reductions in body temperature and locomotor activity induced by i3vt SHU9119 were not reversed by pair feeding, but rather were more pronounced. None of the effects found can be explained by peripheral action of the compound. The obesity effects occurred despite a lack in neuropeptide expression responses in the neuroanatomical range selected across the arcuate (i. e., CART, POMC, and NPY) and paraventricular (i. e., CRH) hypothalamus. The results indicate that reduced activity of the CNS MC pathway promotes fat deposition via both food intake- dependent and -independent mechanisms.
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| 3. |
- Evers, Simon S., et al.
(författare)
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Roman high and low avoidance rats differ in their response to chronic olanzapine treatment at the level of body weight regulation, glucose homeostasis, and cortico-mesolimbic gene expression
- 2017
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Ingår i: Journal of Psychopharmacology. - : SAGE Publications. - 0269-8811 .- 1461-7285. ; 31:11, s. 1437-1452
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Tidskriftsartikel (refereegranskat)abstract
- Olanzapine, an antipsychotic agent mainly used for treating schizophrenia, is frequently associated with body weight gain and diabetes mellitus. Nonetheless, studies have shown that not every individual is equally susceptible to olanzapine's weight-gaining effect. Therefore, Roman high and low avoidance rat strains were examined on their responsiveness to olanzapine treatment. The Roman high avoidance rat shares many behavioral and physiological characteristics with human schizophrenia, such as increased central dopaminergic sensitivity, whereas the Roman low avoidance rat has been shown to be prone to diet-induced obesity and insulin resistance. The data revealed that only the Roman high avoidance rats are susceptible to olanzapine-induced weight gain and attenuated glucose tolerance. Here it is suggested that the specific olanzapine-induced weight gain in Roman high avoidance rats could be related to augmented dopaminergic sensitivity at baseline through increased expression of prefrontal cortex dopamine receptor D1 mRNA and nucleus accumbens dopamine receptor D2 mRNA expression. Regression analyses revealed that olanzapine-induced weight gain in the Roman high avoidance rat is above all related to increased prolactin levels, whereas changes in glucose homeostasis is best explained by differences in central dopaminergic receptor expressions between strains and treatment. Our data indicates that individual differences in dopaminergic receptor expression in the cortico-mesolimbic system are related to susceptibility to olanzapine-induced weight gain.
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