Fos-like immunoreactivity and thirst following hyperosmotic loading in rats with subdiaphragmatic vagotomy

• Published in: Brain research 2002-03, Vol.931 (2), p.159-167
• Main Authors: Starbuck, Elizabeth M, Wilson, Wendy L, Fitts, Douglas A
• Format: Article
• Language: English
• Subjects: Animals; Behavior, Animal - drug effects; Behavior, Animal - physiology; Biological and medical sciences; Body Weight; Brain - anatomy & histology; Brain - drug effects; Brain - metabolism; Diaphragm - innervation; Drinking; Drinking - drug effects; Drinking - physiology; Drinking Behavior - drug effects; Drinking Behavior - physiology; Feeding Behavior - drug effects; Feeding Behavior - physiology; Feeding. Feeding behavior; Fundamental and applied biological sciences. Psychology; Hypernatremia; Immediate early genes; Injections, Intraperitoneal; Intubation, Gastrointestinal; Male; Nucleus of the solitary tract; Osmolar Concentration; Paraventricular nucleus; Proto-Oncogene Proteins c-fos - metabolism; Rats; Rats, Long-Evans; Reaction Time - drug effects; Saline Solution, Hypertonic - pharmacology; Subfornical organ; Supraoptic nucleus; Thirst - drug effects; Thirst - physiology; Vagotomy - methods; Vagus nerve; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(02)02273-4

If receptors in the gut relay information about increases in local osmolality to the brain via the vagus nerve, then vagotomy should diminish this signaling and reduce both thirst and brain Fos-like immunoreactivity (Fos-ir). Water intake in response to hypertonic saline (i.p. or i.g., 1 M NaCl, 1% BW; i.g., 0.6 M NaCl, 0.5% BW) was reduced during 120 min in rats with subdiaphragmatic vagotomy (VGX) compared to sham-VGX rats. Brain Fos-ir was examined in response to both i.g. loads. After the smaller load, VGX greatly reduced Fos-ir in the supraoptic nucleus (SON) and the magnocellular and parvocellular areas of the paraventricular nucleus (PVN). Fos-ir in the subfornical organ (SFO) and nucleus of the solitary tract (NTS) was not affected. After the larger load, VGX significantly reduced Fos-ir in the parvocellular PVN and in the NTS, but not in the other regions. Thus, decreased water intake by VGX rats was accompanied by decreased Fos-ir in the parvocellular PVN after the same treatments, indicating a role for the abdominal vagus in thirst in response to signaling from gut osmoreceptors. The decreased water intake in the VGX group was not reflected as a decrease in Fos-ir in the SFO. Absorption of the larger i.g. load may have activated Fos-ir through more rapidly increasing systemic osmolality, thereby obscuring a role for the vagus at this dose in the SON and magnocellular PVN.