Multisensory Hypothalamic Neurons May Explain Interactions Among Regulatory Systems

Ja, Boulant; Silva, NL

doi:10.1152/physiologyonline.1989.4.6.245

Cited by 13 publications

(11 citation statements)

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“…The presence of hypothalamic neuronal networks with neurons that are able to sense temperature, and other homeostatic drives including osmolality, glucose, reproductive hormones, and baro-and volume-responses (18,71) means that the impact of heat acclimation is much broader. The physiological characteristics of the heat acclimated phenotype have been reviewed extensively, including a detailed summary of human heat acclimation, in Comprehensive Physiology 2012 and 2013 (188,217) and will be referred to briefly when required.…”

Section: Acclimatory Homeostasismentioning

confidence: 99%

Heat Acclimation, Epigenetics, and Cytoprotection Memory

Horowitz

2014

Comprehensive Physiology

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Heat acclimation is a within-life phenotypic adaptation to heat. Plasticity of the thermoregulatory system is crucial for the induction of heat acclimation. In the last two decades, it has become clear that heat causes adaptive shifts in gene expression which adjust the protein balance. These changes are part of the evolvement of the acclimated phenotype. The molecular-cellular aspects of some acclimatory mechanisms that have only been explained by physiological-effectorial mechanisms have been discovered. This review attempts to bridge the gap between the classic physiological heat acclimation profile and the molecular/cellular mechanisms underlying the evolvement of the acclimated phenotype. Heat acclimation leads to leftward and rightward shifts in temperature thresholds of heat dissipation organs and thermal injury, respectively, thereby expanding the acclimated dynamic thermoregulatory range. Interactions between ambient temperature and afferent drives from effector organs to the hypothalamic thermoregulatory center with modifications in warm/cold sensitive neuron ratio and excitability contribute to the threshold changes. The altered threshold for thermal injury is associated with progressive enhancement of inducible cytoprotective networks, including HSP70, HSF1, and HIF-1ɑ. These molecules are also important in acclimatory kinetics. Aspects of cross-adaption, cross-tolerance and interference with heat acclimation are explained using molecular-cellular physiological interactions, with the heart, skeletal muscles, and water secretory glands as models. Lastly, the roles of epigenetic mechanisms in transcriptional regulation during induction of the acclimated phenotype, its decay, and reinduction are discussed. Posttranslational histone modifications in the promoters of hsp70 and hsp90 form part of our prototype model of heat-acclimation-mediated cytoprotective memory.

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Section: Acclimatory Homeostasismentioning

confidence: 99%

Heat Acclimation, Epigenetics, and Cytoprotection Memory

Horowitz

2014

Comprehensive Physiology

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“…Their depolarizing prepotentials allow them to change their FRs in response to changes in the internal temperature and possibly other endogenous factors (e.g., osmolality, glucose, hormones, etc.) (7,8). In addition, the medial-lateral orientation of their dendritic branches allows them to receive and compare synaptic inputs arriving over different afferent pathways.…”

Section: Morphology Of Different Types Of Po/ah Neuronsmentioning

confidence: 99%

Neuronal basis of Hammel's model for set-point thermoregulation

Boulant

2006

Journal of Applied Physiology

175

118

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In 1965, H. T. Hammel proposed a neuronal model to explain set-point thermoregulation. His model was based on a synaptic network encompassing four different types of hypothalamic neurons: i.e., warm-sensitive and temperature-insensitive neurons and heat loss and heat production effector neurons. Although some modifications to this model are suggested, recent electrophysiological and morphological studies support many of the model's major tenets. Hypothalamic warm-sensitive neurons integrate core and peripheral thermal information. These neurons sense changes in hypothalamic temperature, and they orient their dendrites medially and laterally to receive ascending afferent input from cutaneous thermoreceptors. Temperature-insensitive neurons have a different dendritic orientation and may provide constant reference signals, which are important in determining thermoregulatory set points. In Hammel's model, temperature-sensitive and -insensitive neurons send mutually antagonistic synaptic inputs to effector neurons controlling various thermoregulatory responses. The model predicts that warm-sensitive neurons synaptically excite heat loss effector neurons and inhibit heat production effector neurons. In recent studies, one counterpart of these effector neurons may be "excitatory postsynaptic potential-driven neurons," the activity of which is dependent on synaptic excitation from nearby cells. Excitatory postsynaptic potential-driven neurons have sparse dendrites that appear to be specifically oriented, either medially or laterally, presumably to receive selective synaptic input from a discrete source. Another counterpart of effector neurons may be "silent neurons," which have extensive dendritic branches that may receive synaptic excitation from remote sources. Because some silent neurons receive synaptic inhibition from nearby warm-sensitive neurons, Hammel's model would predict that they have a role in heat production or heat retention responses.

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“…Similar I-V relations were reported for paraventricular parvicellular neurons . This suggests three main points: 1) a broad category of hypothalamic parvicellular neurons with a common set of intrinsic electrophysiological properties extends across certain hypothalamic regions; 2 ) cells with these properties constitute the major neuronal type in the SDN-POA and surrounding MPOA, and 3) these properties are a substrate for integrating responses to the several homeostatic stimuli known to affect the activity of cells in this region (Boulant and Silva, 1989). …”

Section: Other Intrinsic Propertiesmentioning

confidence: 99%

Homogeneity of intracellular electrophysiological properties in different neuronal subtypes in medial preoptic slices containing the sexually dimorphic nucleus of the rat

Kim

Gorski

et al. 1994

J of Comparative Neurology

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The sexually dimorphic nucleus of the preoptic area (SDN-POA) is larger in male than in female rats, the male phenotype requiring the presence of circulating androgens perinatally. These experiments investigated the intracellular electrophysiology and morphology of SDN-POA neurons and compared these properties with those of other medial preoptic area (MPOA) neurons. Biocytin-injected cells in the SDN-POA either had one or two primary dendrites, or they had multipolar dendritic arrays; dendrites were aspiny or sparsely spiny and displayed limited branching. Neurons in other parts of the MPOA were similar morphologically. Regardless of morphology, neurons situated in either the SDN-POA or surrounding MPOA had low-threshold potentials and linear or nearly linear current-voltage relations. In most (73%) cells, stimulation of the dorsal preoptic region evoked a fast excitatory postsynaptic potential followed by a fast inhibitory postsynaptic potential (IPSP). Bicuculline blocked the fast IPSPs, which reversed near the Cl2 equilibrium potential (-71 +/- 5 mV), indicating their mediation by gamma-aminobutyric acid (GABA)A receptors. Neurons in the SDN-POA have electrophysiological properties similar to those of other medial preoptic cells. When compared with the hypothalamic paraventricular nucleus, the MPOA appears relatively homogeneous electrophysiologically. This is despite the morphological variability within this population of neurons and heterogeneities that are also apparent at other levels of analysis. Finally, GABA-mediated, inhibitory synaptic contacts are widespread among medial preoptic neurons, consistent with indications from earlier reports that GABA provides a link in the feedback actions of gonadal steroids on the release of gonadotropic hormones.

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Multisensory Hypothalamic Neurons May Explain Interactions Among Regulatory Systems

Cited by 13 publications

References 0 publications

Heat Acclimation, Epigenetics, and Cytoprotection Memory

Heat Acclimation, Epigenetics, and Cytoprotection Memory

Neuronal basis of Hammel's model for set-point thermoregulation

Homogeneity of intracellular electrophysiological properties in different neuronal subtypes in medial preoptic slices containing the sexually dimorphic nucleus of the rat

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