Water deprivation increases Fos immunoreactivity in PVN autonomic neurons with projections to the spinal cord and rostral ventrolateral medulla

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology Vol. 287; no. 5; pp. R1172 - R1183
• Main Authors: Stocker, Sean D, Cunningham, J. Thomas, Toney, Glenn M
• Format: Journal Article
• Language: English
• Published: United States 01.11.2004
• Subjects: Animals; Blood Pressure - physiology; Blood Proteins - metabolism; Hematocrit; Immunohistochemistry; Male; Medulla Oblongata - cytology; Medulla Oblongata - metabolism; Neural Pathways - cytology; Neural Pathways - metabolism; Neurons - metabolism; Oncogene Proteins v-fos - biosynthesis; Oncogene Proteins v-fos - metabolism; Paraventricular Hypothalamic Nucleus - metabolism; Rats; Rats, Sprague-Dawley; Spinal Cord - cytology; Spinal Cord - metabolism; Water Deprivation - physiology
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00394.2004

Departments of 1 Physiology and 2 Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229 Submitted 14 June 2004 ; accepted in final form 15 July 2004 The present study sought to determine whether water deprivation increases Fos immunoreactivity, a neuronal marker related to synaptic activation, in sympathetic-regulatory neurons of the hypothalamic paraventricular nucleus (PVN). Fluorogold (4%, 50 nl) and cholera toxin subunit B (0.25%, 20–30 nl) were microinjected into the spinal cord (T 1 –T 3 ) and rostral ventrolateral medulla (RVLM), respectively. Rats were then deprived of water but not food for 48 h. Water deprivation significantly increased the number of Fos-positive nuclei throughout the dorsal, ventrolateral, and lateral parvocellular divisions of the PVN (water deprived, 215 ± 23 cells; control, 45 ± 7 cells, P < 0.01). Moreover, a significantly greater number of Fos-positive nuclei were localized in spinally projecting (11 ± 3 vs. 2 ± 1 cells, P < 0.025) and RVLM-projecting (45 ± 7 vs. 7 ± 1 cells, P < 0.025) neurons of the PVN in water-deprived vs. control rats, respectively. The majority of these double-labeled neurons was found in the ventrolateral and lateral parvocellular divisions of the ipsilateral PVN. Interestingly, a significantly greater percentage of RVLM-projecting PVN neurons were Fos positive compared with spinally projecting PVN neurons in the ventrolateral (25.8 ± 0.7 vs. 8.0 ± 1.5%, respectively, P < 0.01) and lateral (23.4 ± 2.1 vs. 5.0 ± 0.9%, respectively, P > 0.01) parvocellular divisions. In addition, we analyzed spinally projecting neurons of the RVLM and found a significantly greater percentage were Fos positive in water-deprived rats than in control rats (26 ± 3 vs. 3 ± 1%, respectively; P < 0.001). Collectively, the present findings indicate that water deprivation evokes a distinct cellular response in sympathetic-regulatory neurons of the PVN and RVLM. hyperosmolality; hypovolemia; dehydration; sympathetic outflow; parvocellular Address for reprint requests and other correspondence: S. D. Stocker, Dept. of Physiology, Univ. of Texas HSC at San Antonio, 7703 Floyd Curl Dr. (MC-7756), San Antonio, TX 78229 (E-mail: stocker{at}uthscsa.edu )