title: 5-HT neurons of the area postrema become c-Fos-activated after increases in plasma sodium levels and transmit interoceptive information to the nucleus accumbens.
abstract: Serotonergic (5-hydroxytryptamine, 5-HT) neurons of the area postrema (AP) represent one neuronal phenotype implicated in the regulation of salt appetite. Tryptophan hydroxylase (Tryp-OH, synthetic enzyme-producing 5-HT) immunoreactive neurons in the AP of rats become c-Fos-activated following conditions in which plasma sodium levels are elevated; these include intraperitoneal injections of hypertonic saline and sodium repletion. Non-Tryp-OH neurons also became c-Fos-activated. Sodium depletion, which induced an increase in plasma osmolality but caused no significant change in the plasma sodium concentration, had no effect on the c-Fos activity in the AP. Epithelial sodium channels are expressed in the Tryp-OH-immunoreactive AP neurons, possibly functioning in the detection of changes in plasma sodium levels. Since little is known about the neural circuitry of these neurons, we tested whether the AP contributes to a central pathway that innervates the reward center of the brain. Stereotaxic injections of pseudorabies virus were made in the nucleus accumbens (NAc), and after 4 days, this viral tracer produced retrograde transneuronal labeling in the Tryp-OH and non-Tryp-OH AP neurons. Both sets of neurons innervate the NAc via a multisynaptic pathway. Besides sensory information regarding plasma sodium levels, the AP→NAc pathway may also transmit other types of chemosensory information, such as those related to metabolic functions, food intake, and immune system to the subcortical structures of the reward system. Because these subcortical regions ultimately project to the medial prefrontal cortex, different types of chemical signals from visceral systems may influence affective functions.
authors.affiliation: Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Miller
authors.forename: Arthur D
authors.initials: AD
authors.lastname: Loewy
mesh_terms: D000818:Animals; D001069:Appetite Regulation; D031608:Area Postrema / Q000378:metabolism*; D001522:Behavior, Animal; D011558:Herpesvirus 1, Suid; D007274:Injections, Intraperitoneal; D008297:Male; D009434:Neural Pathways / Q000378:metabolism; D056347:Neuroanatomical Tract-Tracing Techniques; D056325:Neuronal Tract-Tracers; D009714:Nucleus Accumbens / Q000378:metabolism*; D009994:Osmolar Concentration; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012201:Reward; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage / Q000378:metabolism*; D059326:Serotonergic Neurons / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*; D017673:Sodium Chloride, Dietary / Q000097:blood; D009435:Synaptic Transmission; D013997:Time Factors; D014365:Tryptophan Hydroxylase / Q000378:metabolism
chemical_list: D056325:Neuronal Tract-Tracers; D016760:Proto-Oncogene Proteins c-fos; D012462:Saline Solution, Hypertonic; D017673:Sodium Chloride, Dietary; D012701:Serotonin; D014365:Tryptophan Hydroxylase
keywords: area postrema; circumventricular organs; epithelial sodium channels; nucleus accumbens; ventral tegmental area