Limbic control over the homeostatic need for sodium

Sci Rep. 2019 Jan 31;9(1):1050. doi: 10.1038/s41598-018-37405-w.

Abstract

The homeostatic need for sodium is one of the strongest motivational drives known in animals. Although the brain regions involved in the sensory detection of sodium levels have been mapped relatively well, data about the neural basis of the motivational properties of salt appetite, including a role for midbrain dopamine cells, have been inconclusive. Here, we employed a combination of fiber photometry, behavioral pharmacology and c-Fos immunohistochemistry to study the involvement of the mesocorticolimbic dopamine system in salt appetite in rats. We observed that sodium deficiency affected the responses of dopaminergic midbrain neurons to salt tasting, suggesting that these neurons encode appetitive properties of sodium. We further observed a significant reduction in the consumption of salt after pharmacological inactivation of the nucleus accumbens (but not the medial prefrontal cortex), and microstructure analysis of licking behavior suggested that this was due to decreased motivation for, but not appreciation of salt. However, this was not dependent on dopaminergic neurotransmission in that area, as infusion of a dopamine receptor antagonist into the nucleus accumbens did not alter salt appetite. We conclude that the nucleus accumbens, but not medial prefrontal cortex, is important for the behavioral expression of salt appetite by mediating its motivational component, but that the switch in salt appreciation after sodium depletion, although detected by midbrain dopamine neurons, must arise from other areas.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Baclofen / pharmacology
  • Dopamine / metabolism
  • Dopamine Antagonists / pharmacology
  • Dopaminergic Neurons / drug effects
  • Dopaminergic Neurons / metabolism
  • Drinking / drug effects
  • Male
  • Muscimol / pharmacology
  • Nucleus Accumbens / drug effects
  • Nucleus Accumbens / metabolism
  • Prefrontal Cortex / drug effects
  • Prefrontal Cortex / metabolism
  • Proto-Oncogene Proteins c-fos / metabolism
  • Rats
  • Rats, Long-Evans
  • Sodium / metabolism*
  • Synaptic Transmission / drug effects
  • Ventral Tegmental Area / drug effects
  • Ventral Tegmental Area / metabolism

Substances

  • Dopamine Antagonists
  • Proto-Oncogene Proteins c-fos
  • Muscimol
  • Sodium
  • Baclofen
  • Dopamine