Role of the medial and lateral parabrachial nucleus in acquisition and retention of conditioned taste aversion in rats

Abstract The parabrachial nucleus (PBN) is a key nucleus for the regulation of feeding behavior. Inhibitory inputs from the hypothalamus to the PBN play a crucial role in the normal maintenance of feeding behavior, because their loss leads to starvation. Viscerosensory stimuli result in neuronal activation of the PBN. However, the origin and neurochemical identity of the excitatory neuronal input to the PBN remain largely unexplored. Here, we hypothesize that hindbrain glucagon-like peptide 1 (GLP-1) neurons provide excitatory inputs to the PBN, activation of which may lead to a reduction in feeding behavior. Our data, obtained from mice expressing the yellow fluorescent protein in GLP-1-producing neurons, revealed that hindbrain GLP-1-producing neurons project to the lateral PBN (lPBN). Stimulation of lPBN GLP-1 receptors (GLP-1Rs) reduced the intake of chow and palatable food and decreased body weight in rats. It also activated lPBN neurons, reflected by an increase in the number of c-Fos-positive cells in this region. Further support for an excitatory role of GLP-1 in the PBN is provided by electrophysiological studies showing a remarkable increase in firing of lPBN neurons after Exendin-4 application. We show that within the PBN, GLP-1R activation increased gene expression of 2 energy balance regulating peptides, calcitonin gene-related peptide (CGRP) and IL-6. Moreover, nearly 70% of the lPBN GLP-1 fibers innervated lPBN CGRP neurons. Direct intra-lPBN CGRP application resulted in anorexia. Collectively, our molecular, anatomical, electrophysiological, pharmacological, and behavioral data provide evidence for a functional role of the GLP-1R for feeding control in the PBN.

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Gfral-expressing Neurons Suppress Food Intake via Aversive Pathways

10.1101/2020.05.11.088773 ◽

2020 ◽

Author(s):

Paul V. Sabatini ◽

Henriette Frikke-Schmidt ◽

Joe Arthurs ◽

Desiree Gordian ◽

Anita Patel ◽

...

Keyword(s):

Gastric Emptying ◽

Food Intake ◽

Taste Aversion ◽

Conditioned Taste Aversion ◽

Mechanisms Of Action ◽

Parabrachial Nucleus ◽

Gastric Physiology ◽

Anorexigenic Peptide ◽

Artificial Activation ◽

Meal Ingestion

AbstractTo determine the function and mechanisms of action for hindbrain neurons that express GFRAL, the receptor for the anorexigenic peptide, GDF-15, we generated Gfralcre and conditional GfralCreERT mice. While signals of infection or pathophysiologic states (rather than meal ingestion) stimulate GFRAL neurons, the artificial activation of GfralCre- expressing neurons inhibited feeding, decreased gastric emptying, and promoted a conditioned taste aversion (CTA). Additionally, activation of the smaller population of GFRAL neurons captured by the GfralCreERT allele decreased gastric emptying and produced a CTA without suppressing food intake, suggesting that GFRAL neurons primarily modulate gastric physiology and stimulate aversive responses. GFRAL neurons most strongly innervated the parabrachial nucleus (PBN), where they targeted CGRP-expressing (CGRPPBN) neurons. Silencing CGRPPBN neurons abrogated the aversive and anorexic effects of GDF-15. These findings suggest that GFRAL neurons link non-meal-associated, pathophysiologic signals to the aversive suppression of nutrient uptake and absorption.

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Adrenomedullin acts in the lateral parabrachial nucleus to increase arterial blood pressure through mechanisms mediated by glutamate and nitric oxide

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00172.2008 ◽

2008 ◽

Vol 295 (1) ◽

pp. R38-R44 ◽

Cited By ~ 1

Author(s):

Adrian Geambasu ◽

Teresa L. Krukoff

Keyword(s):

Nitric Oxide ◽

Calcium Channel ◽

Male Rats ◽

Parabrachial Nucleus ◽

Dependent Manner ◽

Pressor Effect ◽

Arterial Blood ◽

Lateral Parabrachial Nucleus ◽

Nos Inhibitors

Adrenomedullin (ADM) acts in a site-specific manner within autonomic centers of the brain to modulate mean arterial pressure (MAP). To determine the role of ADM in the pontine autonomic center, the lateral parabrachial nucleus (LPBN), we used urethane-anesthetized adult Sprague-Dawley male rats to test the hypothesis that ADM increases MAP at this site through glutamate- and nitric oxide (NO)-dependent mechanisms. ADM microinjected into the LPBN increased MAP in a dose-dependent manner. The pressor effect of ADM (0.01 pmol) had a peak value of 11.9 ± 1.9 mmHg at 2 min and lasted for 7 min. We demonstrated that ADM's effect is receptor mediated by blocking the effect with the ADM receptor antagonist, ADM22-52. We showed that glutamate mediates ADM's pressor response, as this response was blocked using coinjections of ADM with dizolcipine hydrogen maleate or 6-cyano-7-nitroquinoxaline-2,3-dione, N-methyl-d-aspartate (NMDA) and non-NMDA glutamate receptor antagonists, respectively. We tested the roles of NO with coinjections of ADM with either N5-(1-iminoethyl)-l-ornithine or 7-nitroindazole monosodium salt, nonspecific and neuronal NO synthase (NOS) inhibitors, respectively; both inhibitors blocked ADM's pressor effect. Finally, we studied the role of calcium influx in ADM's pressor effect, as intracellular calcium is important in both glutamate and NO neurotransmission. ADM's effect was blocked when nifedipine, an L-type calcium channel blocker, was coinjected with ADM into the LPBN. This study is the first to show that ADM acts in the LPBN to increase MAP through mechanisms dependent on activation of ionotropic glutamate receptors, neuronal and endothelial NOS-mediated NO synthesis, and L-type calcium channel activation.

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