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Flores RA, Dos-Santos RC, Rodrigues-Santos I, de Jesus AA, Antunes-Rodrigues J, Elias LLK. Tonic noradrenergic input to neurons in the dorsal raphe nucleus mediates food intake in male mice. Behav Brain Res 2024; 462:114872. [PMID: 38266779 DOI: 10.1016/j.bbr.2024.114872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 01/08/2024] [Accepted: 01/18/2024] [Indexed: 01/26/2024]
Abstract
The dorsal raphe nucleus (DRN) is essential for the control of food intake. Efferent projections from the DRN extend to several forebrain regions that are involved in the control of food intake. However, the neurotransmitters released in the DRN related to the control of food intake are not known. We have previously demonstrated that a tonic α1 action on DRN neurons contributes to satiety in the fed rats. In this study we investigated the participation of norepinephrine (NE) signaling in the DRN in the satiety response. Intra-DRN administration of NE causes an increase in the 2-hour food intake of sated mice, an effect that was blocked by previous administration of yohimbine, an α2 antagonist. Similarly, Intra-DRN administration of clonidine, an α2 agonist, increases food intake in sated mice. This result indicates that in the satiated mice exogenous NE acts on α2 receptors to increase food intake. Furthermore, administration of phenylephrine, an α1 agonist, decreases food intake in fasted mice and prazosin, an α1 antagonist, increases food intake in the sated mice. Taken together these results indicate that, in a satiated condition, a tonic α1 adrenergic action on the DRN neurons inhibits food intake and that exogenous NE administered to the DRN acts on α2 adrenergic receptors to increase food intake. These data reinforce the intricate neuronal functioning of the DRN and its effects on feeding.
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Affiliation(s)
- Rafael Appel Flores
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, 3900, Bandeirantes Av., Prof. Dr. Zeferino Vaz Building, ZIP Code: 14049-900, Ribeirão Preto, SP, Brazil.
| | - Raoni C Dos-Santos
- Department of Cell and Molecular Biology, Tulane University, 6602 Freret St, New Orleans, Percival Stern Hall, ZIP Code: 70118, New Orleans, Louisiana, USA.
| | - Isabelle Rodrigues-Santos
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, 3900, Bandeirantes Av., Prof. Dr. Zeferino Vaz Building, ZIP Code: 14049-900, Ribeirão Preto, SP, Brazil
| | - Aline Alves de Jesus
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, 3900, Bandeirantes Av., Prof. Dr. Zeferino Vaz Building, ZIP Code: 14049-900, Ribeirão Preto, SP, Brazil
| | - José Antunes-Rodrigues
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, 3900, Bandeirantes Av., Prof. Dr. Zeferino Vaz Building, ZIP Code: 14049-900, Ribeirão Preto, SP, Brazil
| | - Lucila L K Elias
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, 3900, Bandeirantes Av., Prof. Dr. Zeferino Vaz Building, ZIP Code: 14049-900, Ribeirão Preto, SP, Brazil.
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Flores RA, Dos-Santos RC, Steinbach R, Rodrigues-Santos I, de Jesus AA, Antunes-Rodrigues J, Paschoalini MA. α-1 Adrenoceptor Activation in the Dorsal Raphe Nucleus Decreases Food Intake in Fasted Rats. Front Physiol 2021; 12:775070. [PMID: 34899395 PMCID: PMC8656260 DOI: 10.3389/fphys.2021.775070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 10/21/2021] [Indexed: 01/12/2023] Open
Abstract
The dorsal raphe (DR) nucleus is involved in a myriad of physiological functions, such as the control of sleep-wake cycle, motivation, pain, energy balance, and food intake. We have previously demonstrated that in ad libitum fed rats the intra-DR administration of phenylephrine, an α-1 receptor agonist, does not affect food intake, whereas clonidine, an α-2 receptor agonist, potently stimulates food intake. These results indicated that in fed rats an increased adrenergic tonus blocked food intake, since the activation of α-2 auto-receptors, which decreases pre-synaptic release of adrenaline/noradrenaline, affected food intake. Thus, in this study we assessed whether the response to adrenergic stimuli would differ after overnight fasting, a situation of low adrenergic activity in the DR. Intra-DR administration of adrenaline and noradrenaline blocked food intake evoked by overnight fasting. Similarly, phenylephrine administration decreased hunger-induced food intake. These changes in food intake were accompanied by changes in other behaviors, such as increased immobility time and feeding duration. On the other hand, intra-DR administration of clonidine did not affect food-intake or associated behaviors. These results further support the hypothesis that in fed animals, increased adrenergic tonus in DR neurons inhibiting feeding, while in fasted rats the adrenergic tonus decreases and favors food intake. These data indicate a possible mechanism through which adrenergic input to the DRN contributes to neurobiology of feeding.
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Affiliation(s)
- Rafael Appel Flores
- Department of Physiology, Ribeirão Preto School of Medicine, São Paulo University, Ribeirão Preto, Brazil.,Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina, Florianópolis, Brazil
| | - Raoni Conceição Dos-Santos
- Department of Physiology, Ribeirão Preto School of Medicine, São Paulo University, Ribeirão Preto, Brazil
| | - Renata Steinbach
- Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina, Florianópolis, Brazil
| | - Isabelle Rodrigues-Santos
- Department of Physiology, Ribeirão Preto School of Medicine, São Paulo University, Ribeirão Preto, Brazil
| | - Aline Alves de Jesus
- Department of Physiology, Ribeirão Preto School of Medicine, São Paulo University, Ribeirão Preto, Brazil
| | - José Antunes-Rodrigues
- Department of Physiology, Ribeirão Preto School of Medicine, São Paulo University, Ribeirão Preto, Brazil
| | - Marta Aparecida Paschoalini
- Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina, Florianópolis, Brazil
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Bhave VM, Nectow AR. The dorsal raphe nucleus in the control of energy balance. Trends Neurosci 2021; 44:946-960. [PMID: 34663507 DOI: 10.1016/j.tins.2021.09.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 09/04/2021] [Accepted: 09/23/2021] [Indexed: 01/07/2023]
Abstract
Energy balance is orchestrated by an extended network of highly interconnected nuclei across the central nervous system. While much is known about the hypothalamic circuits regulating energy homeostasis, the 'extra-hypothalamic' circuits involved are relatively poorly understood. In this review, we focus on the brainstem's dorsal raphe nucleus (DRN), integrating decades of research linking this structure to the physiologic and behavioral responses that maintain proper energy stores. DRN neurons sense and respond to interoceptive and exteroceptive cues related to energy imbalance and in turn induce appropriate alterations in energy intake and expenditure. The DRN is also molecularly differentiable, with different populations playing distinct and often opposing roles in controlling energy balance. These populations are integrated into the extended circuit known to regulate energy balance. Overall, this review summarizes the key evidence demonstrating an important role for the DRN in regulating energy balance.
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Affiliation(s)
- Varun M Bhave
- Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA; Harvard Medical School, Boston, MA 02115, USA
| | - Alexander R Nectow
- Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
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