RESUMO
High-fat foods tend to be palatable and can cause addiction in mice via a reinforcing effect. However, mice showed preference for low fat concentrations that do not elicit a reinforcing effect in a two-bottle choice test with water as the alternative. This behavior indicates the possibility that the mechanism underlying fat palatability may differ depending on the dietary fat content. To address this issue, we examined the influences of the opioid system and olfactory and gustatory transductions on the intake and reinforcing effects of various concentrations of a dietary fat emulsion (Intralipid). We found that the intake and reinforcing effects of fat emulsion were reduced by the administration of an opioid receptor antagonist (naltrexone). Furthermore, the action of naltrexone was only observed at higher concentrations of fat emulsion. The intake and the reinforcing effects of fat emulsion were also reduced by olfactory and glossopharyngeal nerve transections (designated ONX and GLX, respectively). In contrast to naltrexone, the effects of ONX and GLX were mainly observed at lower concentrations of fat emulsion. These results imply that the opioid system seems to have a greater role in determining the palatability of high-fat foods unlike the contribution of olfactory and glossopharyngeal nerves.
Assuntos
Gorduras na Dieta/metabolismo , Preferências Alimentares/fisiologia , Naltrexona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Reforço Psicológico , Animais , Gorduras na Dieta/administração & dosagem , Emulsões/administração & dosagem , Emulsões/metabolismo , Emulsões Gordurosas Intravenosas/administração & dosagem , Emulsões Gordurosas Intravenosas/metabolismo , Traumatismos do Nervo Glossofaríngeo/induzido quimicamente , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Traumatismos do Nervo Olfatório/induzido quimicamente , Fosfolipídeos/administração & dosagem , Fosfolipídeos/metabolismo , Óleo de Soja/administração & dosagem , Óleo de Soja/metabolismoRESUMO
Bilateral transection of the glossopharyngeal nerves (GLOx) disrupts the immune-to-brain communication from the posterior oral cavity. The current report tested whether this effect is due to the afferent (sensory) or efferent (parasympathetic motor) components of the nerve. Injection of lipopolysaccharide (LPS) into the soft palate (ISP) of GLOx or sham-operated (SHAM) rats increased the circulating levels of interleukin-1beta (IL-1beta), interleukin-1 receptor antagonist (IL-1ra) and corticosterone (CORT), as well the hypothalamic content of IL-1beta; no difference in circulating levels and hypothalamic content was found between GLOx and SHAM at 2 and 4.5 h after LPS injection. These results indicate that glossopharyngeal neural efferents do not mediate the effects of GLOx on the immune-to-brain communication.