Differential stimulation of c-fos expression in hypothalamic nuclei of the rat brain during short-term heat acclimation and mild dehydration

Patronas, Panagiotis; Horowitz, Michal; Simón, E.; Gerstberger, Rüdiger

doi:10.1016/s0006-8993(98)00405-3

Cited by 66 publications

(51 citation statements)

References 43 publications

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“…The Fos-immunoreactivity is known to link with their neural activity. This increase in Fos-immunoreactive neurons was also reported in animals exposed to a hot environment [27][28][29][30] . The warm-sensitive neurons in the PO were reported to respond to skin and/or spinal temperature too 21) .…”

Section: Warm-sensitive Neurons In the Hypothalamussupporting

confidence: 79%

“…These results may suggest that osmotic stimulation attenuates the central thermosensitivity to heat, resulting in the suppression of autonomic heat loss responses. In contrast, heat exposure increases Fos-immunoreactive neurons in the median preoptic nucleus 70) , and the combination of heat and osmotic stimuli additively augments the number of Fosimmunoreactive neurons 79) . Thus, the influence of osmotic signal on the warm-sensitive neurons may be different among the areas in the PO.…”

Section: Non-thermoregulatory Factors Influencing On Thermoregulationmentioning

confidence: 94%

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Central Mechanisms for Thermoregulation in a Hot Environment

Nagashima

2006

INDUSTRIAL HEALTH

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Homeothermic animals regulate body temperature by autonomic and behavioral thermoeffector responses. The regulation is conducted mainly in the brain. Especially, the preoptic area (PO) in the hypothalamus plays a key role. The PO has abundant warm-sensitive neurons, sending excitatory signals to the brain regions involved in heat loss mechanisms, and inhibitory signals to those involved in heat production mechanisms. The sympathetic fibers determine tail blood flow in rats, which is an effective heat loss process. Some areas in the midbrain and medulla are involved in the control of tail blood flow. Recent study also showed that the hypothalamus is involved in heat escape behavior in rats. However, our knowledge about behavioral regulation is limited. The central mechanism for thermal comfort and discomfort, which induce various behavioral responses, should be clarified. In the heat, dehydration affects both autonomic and behavioral thermoregulation by non-thermoregulatory factors such as high Na + concentration. The PO seems to be closely involved in these responses. The knowledge about the central mechanisms involved in thermoregulation is important to improve industrial health, e.g. preventing accidents associated with the heat or organizing more comfortable working environment.

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Section: Warm-sensitive Neurons In the Hypothalamussupporting

confidence: 79%

Section: Non-thermoregulatory Factors Influencing On Thermoregulationmentioning

confidence: 94%

Central Mechanisms for Thermoregulation in a Hot Environment

Nagashima

2006

INDUSTRIAL HEALTH

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“…However, in one study (7) fetal plasma composition changes were not quantified, and maternal mannitol-induced plasma hypertonicity may have induced fetal plasma volume contraction, contributing to central dipsogenic stimulation. In a subsequent study (12), pain or stress from intraperitoneal fetal hypertonic injections may have induced central c-fos expression (13,14). Notably, neither of the previous studies simultaneously confirmed fetal swallowing activity in relation to c-fos expression.…”

Section: Discussionmentioning

confidence: 87%

“…However, stress and pain (potentially in response to intraperitoneal hypertonicity) may induce c-fos expression in similar areas as that induced by osmotic stimuli (e.g. PVN and SON) (13,14).…”

mentioning

confidence: 99%

Plasma Osmolality Dipsogenic Thresholds and c-fos Expression in the Near-Term Ovine Fetus

Nijland

Ross

2001

Pediatr Res

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In ovine and human pregnancy, fetal swallowing contributes importantly to amniotic fluid homeostasis. Fetal dipsogenic responsiveness to short-term plasma hyperosmolality develops in late gestation, although fetal swallowing is not stimulated in response to long-term plasma osmolality increases (2 to 3%), which typically stimulate adult drinking behavior. To explore the near-term fetal plasma osmolality threshold for swallowing stimulation, we examined the effects of i.v. hypertonic saline-induced subacute increases in plasma hypertonicity on fetal swallowing behavior. Central sites of activation were examined by c-fos expression in putative dipsogenic nuclei. The results demonstrate that subacute 2 to 3% plasma osmolality increases do not stimulate near-term ovine fetal swallowing. However, fetal swallowing activity significantly increased (3 times) after plasma osmolality increased Ͼ6% above basal values. Consistent with a specific dipsogenic response, i.v. hypertonic saline induced c-fos expression in the anterior third ventricle region, a putative dipsogenic center, as well as in the fetal hindbrain. The stimulation of fetal swallowing under conditions of higher osmotic stimulation and the correlation with forebrain c-fos expression indicates that near-term fetal osmoregulation mechanisms are functional, although not completely mature. Intravascular osmolality and body fluid homeostasis are maintained primarily by coordination of thirst-mediated drinking behavior and neuroendocrine-mediated renal fluid regulatory mechanisms. During in utero development, fetal swallowing contributes importantly to amniotic fluid volume homeostasis. Previous studies in this laboratory have demonstrated that near-term ovine fetal swallowing is stimulated by intravenous, intracarotid, and intracerebroventricular hyperosmolality (1-4), consistent with the activation of central osmoreceptors in regions responsive to both vascular and cerebrospinal fluid tonicity. Despite intact fetal osmotic-dipsogenic responsiveness, fetal swallowing is not stimulated in response to plasma osmolality increases (2 to 3%), which typically stimulate adult drinking behavior. For example, despite continually elevated plasma osmolality (10 -14 mosmol/kg) in response to short-term i.v. hypertonic saline injection, fetal swallowing activity is only stimulated for a maximum of 5 min (1). Furthermore, long-term increases in plasma osmolality of 10 mosmol/kg do not alter fetal swallowed volume (5). These responses suggest either a reduced population of fetal osmoreceptor cells, reduced sensitivity of osmoreceptors, or altered secondary neural mechanisms, in comparison to the adult. c-fos expression has been well described as a marker of neuronal activation in both adult and fetal brain nuclei (6). McDonald et al. (7) recently showed that FOS-ir was evident in the SFO, OVLT, and MnPO, as well as in the PVN and SON of the near-term fetal forebrain in response to maternal hypertonicity. These results are comparable to physiological and c-fos responses observe...

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“…Swanson, 1986Swanson, , 1988. The identity, however, of the precise preoptic subnuclei (Simerly & Swanson, 1988;Patronas et al 1998) involved in activating heat loss mechanisms remains unclear.…”

Section: Hypothalamus and Thermoregulationmentioning

confidence: 99%