Anorexigenic effects of naltrexone in rats
type: CreativeWork
description: The accessibility of cheap, palatable, and caloric food in the industrialized world has shifted the primary drive of eating behavior from hunger to pleasure; this change has played a significant role in the rise in the prevalence of obesity. Sugary and fatty foods are among the most preferred and, therefore, overconsumed tastants. Opioids are key neuropeptides that propel feeding for reward. Importantly, blocking the opioid receptors in laboratory animals and humans decreases intake of and preference for those diets that are highly palatable. One of those opioid receptor blockers, a non-selective antagonist naltrexone (NTX), has been used in animal and clinical studies related to excessive appetite. Consequently, NTX in combination with another molecule, bupropion, has been approved as a pharmaceutical to treat obesity. This success underscores the need for further characterization of anorexigenic potential of NTX to determine its effects in various eating behavioral contexts/scenarios, in pathophysiological conditions characterized by overeating, as well as in treatment strategies that utilize potential synergy with other molecules that decrease appetite. Therefore, as an overarching goal of this thesis I set forth to further explore anorexigenic potential of NTX as a suppressant of palatability-driven consumption. Previous studies indicate that rats cannot discriminate NTX from saline, except at very high doses. However, in those discrimination experiments, NTX-treated animals had not been fed palatable foods, i.e., diets whose consumption affects the endogenous opioid system thereby potentially leading to changes in sensitivity to opioid receptor blockade. Thus, in Specific Aim 1, I investigated the ability of rats to discriminate between NTX and saline subjected to chronic intermittent sucrose consumption. In the experiments I used the operant setting to determine whether chronic intermittent 25% sucrose solution consumption allows rats to discriminate periphera…
abstract: The accessibility of cheap, palatable, and caloric food in the industrialized world has shifted the primary drive of eating behavior from hunger to pleasure; this change has played a significant role in the rise in the prevalence of obesity. Sugary and fatty foods are among the most preferred and, therefore, overconsumed tastants. Opioids are key neuropeptides that propel feeding for reward. Importantly, blocking the opioid receptors in laboratory animals and humans decreases intake of and preference for those diets that are highly palatable. One of those opioid receptor blockers, a non-selective antagonist naltrexone (NTX), has been used in animal and clinical studies related to excessive appetite. Consequently, NTX in combination with another molecule, bupropion, has been approved as a pharmaceutical to treat obesity. This success underscores the need for further characterization of anorexigenic potential of NTX to determine its effects in various eating behavioral contexts/scenarios, in pathophysiological conditions characterized by overeating, as well as in treatment strategies that utilize potential synergy with other molecules that decrease appetite. Therefore, as an overarching goal of this thesis I set forth to further explore anorexigenic potential of NTX as a suppressant of palatability-driven consumption. Previous studies indicate that rats cannot discriminate NTX from saline, except at very high doses. However, in those discrimination experiments, NTX-treated animals had not been fed palatable foods, i.e., diets whose consumption affects the endogenous opioid system thereby potentially leading to changes in sensitivity to opioid receptor blockade. Thus, in Specific Aim 1, I investigated the ability of rats to discriminate between NTX and saline subjected to chronic intermittent sucrose consumption. In the experiments I used the operant setting to determine whether chronic intermittent 25% sucrose solution consumption allows rats to discriminate periphera…
author: Keembiya Liyanagamage, Donisha Shani Niharika
keywords: Palatability Naltrexone c-Fos immunoreactivity, Brain reward system
license: https://researchcommons.waikato.ac.nz/bitstreams/02587d2c-cdea-4585-b67e-df7d6c8dcd53/download
date published: 2023
date modified: 2026-07-24T05:57:36Z
provider: University Waikato
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: The University of Waikato