Characteristics of resting membrane potentials and synaptic activity in temperature sensitive and insensitive hypothalamic neurons
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| Language: | English |
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The Ohio State University / OhioLINK
2004
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| Online Access: | http://rave.ohiolink.edu/etdc/view?acc_num=osu1086184948 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-osu1086184948 |
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English |
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NEURONS temperature insensitive PO/AH thermosensitivity IPSCs temperature insensitive neurons insensitive neurons |
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NEURONS temperature insensitive PO/AH thermosensitivity IPSCs temperature insensitive neurons insensitive neurons Zhao, Yanmei Characteristics of resting membrane potentials and synaptic activity in temperature sensitive and insensitive hypothalamic neurons |
| author |
Zhao, Yanmei |
| author_facet |
Zhao, Yanmei |
| author_sort |
Zhao, Yanmei |
| title |
Characteristics of resting membrane potentials and synaptic activity in temperature sensitive and insensitive hypothalamic neurons |
| title_short |
Characteristics of resting membrane potentials and synaptic activity in temperature sensitive and insensitive hypothalamic neurons |
| title_full |
Characteristics of resting membrane potentials and synaptic activity in temperature sensitive and insensitive hypothalamic neurons |
| title_fullStr |
Characteristics of resting membrane potentials and synaptic activity in temperature sensitive and insensitive hypothalamic neurons |
| title_full_unstemmed |
Characteristics of resting membrane potentials and synaptic activity in temperature sensitive and insensitive hypothalamic neurons |
| title_sort |
characteristics of resting membrane potentials and synaptic activity in temperature sensitive and insensitive hypothalamic neurons |
| publisher |
The Ohio State University / OhioLINK |
| publishDate |
2004 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=osu1086184948 |
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AT zhaoyanmei characteristicsofrestingmembranepotentialsandsynapticactivityintemperaturesensitiveandinsensitivehypothalamicneurons |
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1719425983444942848 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-osu10861849482021-08-03T05:48:57Z Characteristics of resting membrane potentials and synaptic activity in temperature sensitive and insensitive hypothalamic neurons Zhao, Yanmei NEURONS temperature insensitive PO/AH thermosensitivity IPSCs temperature insensitive neurons insensitive neurons The preoptic-anterior hypothalamus (PO/AH) is a major neural area for sensing body temperature and integrating this information with afferent inputs from peripheral thermoreceptors. The PO/AH contains both warm sensitive neurons and various types of temperature insensitive neurons. These neurons form synaptic networks that control different physiological and behavioral thermoregulatory responses. The present series of experiments focused on the cellular mechanisms that account for neuronal thermosensitivity and the types of synapses that constitute PO/AH neuronal networks. Intracellular recordings were made from neurons in rat hypothalamic tissue slices. Current clamp recordings measured the resting membrane potentials and postsynaptic potentials during either temperature changes or manipulations of synaptic activity. Similarly, voltage clamp recordings measured resting and postsynaptic currents during these same conditions. Mechanisms of neuronal thermosensitivity. PO/AH warm sensitive neurons increase their firing rates with increasing temperatures, while the firing rates of temperature insensitive neurons remain relative constant. Previous studies suggested that the main mechanism for neuronal warm-sensitivity is a thermally-induced depolarization due to inward cationic (Na+ and Ca++) currents. One often-cited study (Kiyohara at al., 1990), in particular, indicated that warm sensitive neurons possess a tetrodotoxin-sensitive resting Na+ current that accounts for their thermosensitivity. The present study examined the effects of temperature on the resting membrane potentials and inward currents in different types of PO/AH neurons. Similar responses were observed in both warm sensitive and temperature insensitive neurons. All neurons displayed slight depolarization during temperature increases and hyperpolarization during temperature decreases; and there was no correlation between neuronal (firing rate) thermosensitivity and resting membrane potential thermosensitivity. Also, all neurons displayed similar thermally-induced changes in their resting currents. These currents increased slightly during tissue warming and decreased during tissue cooling; and again, there was no correlation between neuronal thermosensitivity and resting current thermosensitivity. In addition, the Na+ channel blocker, tetrodotoxin (TTX), reduced current thermosensitivities in both temperature insensitive neurons and warm sensitive neurons. These results suggested that thermosensitive resting membrane potentials, resting currents, as well as persistent, TTX-sensitive sodium currents are not the mechanisms for neuronal warm-sensitivity. Synaptic characteristics. The second series of experiments examined the types of synapses that occur within the PO/AH neuronal network. Voltage clamp experiments measured the excitatory postsynaptic currents (EPSCs) and inhibitory postsynaptic currents (IPSCs) for the different neuronal types. EPSCs and IPSCs exist in both warm sensitive and temperature insensitive neurons; however, warm sensitive neurons have more IPSCs and less EPSCs than the different groups of temperature insensitive neurons. These experiments also examined the neurotransmitters responsible PO/AH synaptic activity. Glutamate caused most of the EPSCs, and GABA (i.e, GABAA receptor) caused most of the IPSCs. Kynurenic acid (a broad spectrum glutamate receptor antagonist) blocked most EPSCs, and bicuculline methiodide (GABAA receptor antagonist) blocked almost all IPSCs. Moreover, TTX attenuated most synaptic currents in warm sensitive neurons and temperature insensitive neurons; and those synaptic currents that were insensitive to TTX were completed blocked by Na+-free medium. This suggests that the recorded postsynaptic activity was due to neurotransmitter released in response to membrane depolarization in presynaptic fibers. 2004-06-21 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1086184948 http://rave.ohiolink.edu/etdc/view?acc_num=osu1086184948 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |