Regional differences in the expression of Fos-like immunoreactivity after central salt loading in conscious rats: modulation by endogenous vasopressin and role of the area postrema.
In this study, we examined the quantitative relationship between centrally administered hypertonic saline (HS) concentrations and the expression of Fos-like immunoreactivity (FLI) in brain regions involved in the homeostasis of body fluids. The regions examined were the organum vasculosum laminae terminalis (OVLT), the median preoptic nucleus (MnPO), the subfornical organ (SFO), the paraventricular nucleus (PVN), the supraoptic nucleus of the hypothalamus, the nucleus of the solitary tract (NTS), and the area postrema (AP). The experiments were performed in conscious rats with attention to the actual changes in central [Na(+)]. Hypertonic saline (0.3, 0.67, or 1.0 M) was delivered at 1 microl/min for 20 min. The changes in cerebrospinal fluid [Na(+)] during i.c.v. administration of 0.3 M hypertonic saline were compatible with those expected for thermal dehydration. FLI increased in a dose-dependent manner in the dorsomedial cap of the PVN and NTS. Although the pressor responses during central salt loading were not significantly affected by pretreatment with the peripheral vasopressin V(1) receptor antagonist OPC-21268, FLI expression in the PVN was significantly augmented. In addition, in AP-lesioned rats, FLI expression in the lateral magnocellular part of the PVN and NTS was significantly enhanced after central salt loading. These results suggest that the peripheral vasopressin system participates in negative feedback to modulate neuronal activities in the PVN, probably through the AP or direct action at the PVN in response to central osmotic and/or Na(+) stimulation.
Kato
Kazuo
K
Department of Physiology, Miyazaki Medical College, 5200 Kihara, Kiyotake-cho, Miyazaki-gun, Miyazaki 889-1692, Japan.
Chu
Chun-Ping
CP
Kannan
Hiroshi
H
Ishida
Yasushi
Y
Nishimori
Toshikazu
T
Nose
Hiroshi
H
D000818:Animals; D065092:Antidiuretic Hormone Receptor Antagonists; D031608:Area Postrema / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D002452:Cell Count / Q000379:methods; D003243:Consciousness / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D017736:Ion-Selective Electrodes; D008297:Male; D010880:Piperidines / Q000494:pharmacology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D015363:Quinolones / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage; D012492:Salts / Q000494:pharmacology*; D012964:Sodium; D017552:Solitary Nucleus / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D014667:Vasopressins / Q000502:physiology*
D065092:Antidiuretic Hormone Receptor Antagonists; D010880:Piperidines; D016760:Proto-Oncogene Proteins c-fos; D015363:Quinolones; D012462:Saline Solution, Hypertonic; D012492:Salts; D014667:Vasopressins; C068644:OPC 21268; D012964:Sodium