American journal of physiology. Regulatory, integrative and comparative physiology
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Aug 2010
Noradrenergic neurons of the area postrema mediate amylin's hypophagic action.
Circulating amylin inhibits food intake via activation of the area postrema (AP). The aim of this study was to identify the neurochemical phenotype of the neurons mediating amylin's hypophagic action by immunohistochemical and feeding studies in rats. Expression of c-Fos protein was used as a marker for neuronal activation and dopamine-beta-hydroxylase (DBH), the enzyme-catalyzing noradrenaline synthesis, as a marker for noradrenergic neurons. ⋯ The AP and nucleus of the solitary tract (NTS) were stained for DBH to assess noradrenaline lesion success and for c-Fos expression to evaluate amylin-induced neuronal activation. In contrast to sham-lesioned animals, noradrenaline-lesioned rats did not show a significant increase in amylin-induced c-Fos expression in the AP and NTS. We conclude that the noradrenergic neurons in the AP mediate at least part of amylin's hypophagic effect.
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Jul 2010
Carotid sinus nerve stimulation, but not intermittent hypoxia, induces respiratory LTF in adult rats exposed to neonatal intermittent hypoxia.
We tested the hypothesis that exposure to neonatal intermittent hypoxia (n-IH) in rat pups alters central integrative processes following acute and intermittent peripheral chemoreceptor activation in adults. Newborn male rats were exposed to n-IH or normoxia for 10 consecutive days after birth. We then used both awake and anesthetized 3- to 4-mo-old rats to record ventilation, blood pressure, and phrenic and splanchnic nerve activities to assess responses to peripheral chemoreflex activation (acute hypoxic response) and long-term facilitation (LTF, long-term response after intermittent hypoxia). ⋯ In n-IH rats, respiratory LTF was not apparent in awake and anesthetized animals. Following intermittent electrical stimulation, however, phrenic LTF was clearly present in n-IH rats, being similar in magnitude to controls. We conclude that, in adult n-IH rats: 1) arterial blood pressure is elevated, 2) peripheral chemoreceptor responses to hypoxia and its central integration are not altered, but splanchnic nerve response is suppressed, 3) LTF is suppressed, and 4) the mechanisms involved in the generation of LTF are still present but are masked most probably as the result of an augmented inhibitory response to hypoxia in the central nervous system.
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Jul 2010
Thermoregulatory, behavioral, and metabolic responses to heatstroke in a conscious mouse model.
The typical core temperature (T(c)) profile displayed during heatstroke (HS) recovery consists of initial hypothermia followed by delayed hyperthermia. Anecdotal observations led to the conclusion that these T(c) responses represent thermoregulatory dysfunction as a result of brain damage. We hypothesized that these T(c) responses are mediated by a change in the temperature setpoint. ⋯ Cellular damage (hematoxylin and eosin staining) was undetectable in the hypothalamus or other brain regions in severe HS mice. Overall, decreases and increases in T(c) were associated with behavioral and autonomic thermoeffectors that suggest HS elicits anapyrexia and fever, respectively. Taken together, T(c) responses of mild and severe HS mice suggest a need for reinterpretation of the mechanisms of thermoregulatory control during recovery.
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Jun 2010
P2Y2 receptors mediate ATP-induced resensitization of TRPV1 expressed by kidney projecting sensory neurons.
The transient receptor potential vanilloid type 1 (TRPV1) channel is a ligand-gated cation channel expressed by sensory nerves. P2Y receptors are G protein-coupled receptors that are also expressed by TRPV1-positive sensory neurons. Therefore, we studied interactions between P2Y receptors and TRPV1 function on kidney projecting sensory neurons. ⋯ Suramin, a P2Y(2) receptor antagonist, blocked resensitization caused by UTP. Immunocytochemical studies showed that FB-labeled neurons coexpressed P2Y(2) receptors and TRPV1. We conclude that P2Y(2) receptor activation can maintain TRPV1 function perhaps during sustained episodes of activity of kidney projecting sensory neurons.
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Jun 2010
ReviewThe Walter B. Cannon Memorial Award Lecture, 2009. Physiology in perspective: The wisdom of the body. In search of autonomic balance: the good, the bad, and the ugly.
Walter B. Cannon's research on the sympathetic nervous system and neurochemical transmission was pioneering. Wisdom has endowed our body with a powerful autonomic neural regulation of the circulation that provides optimal perfusion of every organ in accordance to its metabolic needs. ⋯ This short review, presented as The Walter B. Cannon Memorial Award Lecture for 2009, addresses the mechanisms that disrupt sensory signaling and result in a chronic maladjustment of the autonomic neural output that in many cardiovascular diseases results in excessive increases in the risks of dying. The hopes for any reduction of those risks resides in an understanding of the molecular determinants of neuronal signaling.