Differential Activation of Nitrergic Hypothalamic Neurons by Heat Exposure and Dehydration

Gerstberger, Rüdiger; Barth, Stefan; Horowitz, Michal; Hudl, K.; Patronas, Panagiotis; Hübschle, Thomas

doi:10.1007/978-4-431-67035-3_5

Cited by 4 publications

(2 citation statements)

References 102 publications

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“…Previous studies have found that 24 -48 h of water deprivation, in which body weight fell by ϳ10% (after 24-h deprivation), resulted in an increase in the expression of nitric oxide synthase (the enzyme responsible for the production of nitric oxide) within the PVN (15,16,61). However, exposing the animals to a warm external environment of 34°C for 2 days did not have such an effect (16). These results suggest that a warm external environment may not be sufficient to increase the NADPH-d positive neurons in the PVN.…”

Section: Discussionmentioning

confidence: 99%

Activation of spinally projecting and nitrergic neurons in the PVN following heat exposure

Cham¹,

Klein²,

Owens³

et al. 2006

American Journal of Physiology-Regulatory, Integrative and Comp

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. Activation of spinally projecting and nitrergic neurons in the PVN following heat exposure. Am J Physiol Regul Integr Comp Physiol 291: R91-R101, 2006; doi:10.1152/ajpregu.00675.2005.-The present study investigated the effect of acute thermal stimulation in conscious rats on the production of Fos, a marker of increased neuronal activity, in spinally projecting and nitrergic neurons in the hypothalamic paraventricular nucleus (PVN). The PVN contains a high concentration of nitrergic neurons, as well as neurons that project to the intermediolateral cell column (IML) of the spinal cord that can directly influence sympathetic nerve activity (SNA). During thermal stimulation, the PVN is activated, but it is unknown whether spinally projecting PVN neurons and the nitrergic neurons are involved. Compared with controls, rats exposed to an environmental temperature of 39°C for 1 h had a 10-fold increase in the number of cells producing Fos in the PVN (133 Ϯ 23 vs. 1,336 Ϯ 43, respectively, P Ͻ 0.0001). Of the spinally projecting neurons in the PVN of heated rats (98 Ϯ 10), over 20% expressed Fos. Additionally, of the nitrergic neurons (NADPH-diaphorase positive) located in the parvocellular PVN (723 Ϯ 17), ϳ40% also expressed Fos (P Ͻ 0.0001 compared with controls). Finally, there was a significant increase in the number of spinally projecting neurons in the PVN that were nitrergic and expressed Fos after heat exposure (12%) compared with controls (0.1%) (P Ͻ 0.0001). These results suggest that spinally projecting and nitrergic neurons in the PVN may contribute to the central pathways activated by thermal stimulation. Fos immunohistochemistry; spinally projecting EXPOSURE TO A HOT TEMPERATURE challenge elicits responses mediated in part by the autonomic nervous system to promote heat loss and maintain body fluid homeostasis. Such responses include sweating, an increase in heart rate, increased respiration rate, skin vasodilation, and visceral vasoconstriction in humans; increased salivary secretion in rodents; and tail vasodilation in rats (25,27). The latter autonomic cardiovascular responses often involve changes in sympathetic nerve activity (SNA) and result in the redistribution of blood flow from the viscera to the skin. These changes are mediated by the central nervous system (CNS) (24,25,40,43,45,52,65).It has been well established that the CNS is essential in the regulation of body temperature. There are several brain regions that are likely to contribute to the CNS pathways that mediate the thermoregulatory responses. Studies using the marker of neuronal activation, Fos, or electrophysiological recordings have shown that several forebrain areas are activated after the elevation in body temperature (2, 5-7, 21, 28, 34, 38, 39, 42, 52, 53). These forebrain areas include the preoptic area, anterior hypothalamus, and the paraventricular nucleus (PVN) of the hypothalamus. The preoptic area and anterior hypothalamus are well known key thermoregulatory sites within the brain; however, a role of the PVN in thermoreg...

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Section: Discussionmentioning

confidence: 99%

Activation of spinally projecting and nitrergic neurons in the PVN following heat exposure

Cham¹,

Klein²,

Owens³

et al. 2006

American Journal of Physiology-Regulatory, Integrative and Comp

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“…The MnPO has long been known also to be a crucial site for drinking and body fluid regulation (8). In addition, strong Fos-IR is seen in the MnPO when rats are dehydrated.…”

Section: Discussionmentioning

confidence: 99%

Brain regions expressing Fos during thermoregulatory behavior in rats

Maruyama¹,

Nishi

Konishi

et al. 2003

American Journal of Physiology-Regulatory, Integrative and Comp

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We surveyed the neural substrata for behavioral thermoregulation with immunohistochemical analysis of the expression of Fos protein in the rat brain. We used an operant system in which a rat exposed to heat (40 degrees C) could get cold air (0 degrees C) for 30 s when it moved into the reward area. Rats moved in and out of the reward area of the system periodically and thus maintained their body temperature at a normal level. In the rats performing heat escape behavior (active group), strong Fos immunoreactivity (Fos-IR) was found in the median preoptic nucleus (MnPO), parastrial nucleus (PS), and dorsomedial hypothalamus (DMH) compared with the controls. Another group of rats (passive group) were given the same temperature changes, regardless of the rat's movement, as those obtained by rats of the active group. Fos-IR in the MnPO was also seen in this group. The present results suggest that the PS and DMH play an important role in the genesis of thermoregulatory behavior, whereas the MnPO may be important for detecting changes in ambient and/or body temperatures.

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