Saker, Louise (2008) Metabolic and serotonergic modulation of hypothalamic arcuate nucleus neurones in vitro. PhD thesis, University of Warwick.

	PDF (Thesis text) WRAP_THESIS_Saker_2008.pdf - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader Download (36Mb)
	PDF (Author declaration form) Warwick_thesis_form.pdf Restricted to Repository staff only - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader Download (55Kb)

Abstract

1. The effects of glucose on the electrophysiological properties of rat hypothalamic arcuate nucleus (ARC) neurones were investigated. Neurones were recorded in 10 mM (hyperglycaemic) and 2 mM (euglycaemic) glucose-containing aCSF. The major findings were that input resistance increased in 10 mM glucose, there was an increase in the activity of neurones in 2 mM glucose and there were a greater percentage of neurones expressing lh in 10 mM glucose. Subthreshold active conductances were differentially expressed in ARC neurones including: anomalous inward rectification Q. ), time- and voltage-dependent inward rectification 00, A-like transient outward rectification (IA) and T-type calcium-like conductance. Characterisation of the differential expression of these conductances may represent one way of functionally classifying ARC neurones. 2. Whole-cell patch clamp recording techniques were used in isolated hypothalamic brain slice preparations to investigate the effects of 5-HT on ARC neurones. Bath application of 5-HT induced a membrane depolarisation in a sub-population of ARC neurones (30%), a response that persisted in the presence of TTX indicating a direct effect. 5-HT excited ARC neurones through three potential mechanisms: closure of one or more resting potassium conductances; activation of a non-selective cation channel, or a combination of the two; or activation of a pump in the membrane. This response was mediated through the 5-HT2A. 5-HT2B and/or 5-HT2C receptors revealed using a range of 5-HT receptor agonists and antagonists. 5-HT was shown to excite CART-expressing neurones suggesting an anorexigenic role for 5-HT, via 5-HT2 receptors at the level of the ARC. 3.5-HT induced a membrane hyperpolarisation in a sub-population of ARC neurones (37%). The 5-HT-induced hyperpolarisation persisted in the presence of TTX indicating a direct effect on ARC neurones. 5-HT inhibited ARC neurones most likely through the activation of one or more potassium conductances,including an inwardly rectifying potassium conductance. Potential roles for 5-HTIA, 5-HTIB and 5-HT7 receptors were suggested from studies utilising 5-HT receptor agonists and antagonists. 5-HT inhibited orexigenic NPY/AgRP neurones, identified by their response to ghrelin and by their electrophysiological properties, suggesting an anorexigenic role for 5-HT, acting via 5-HTI and 5-HT7 receptors on NPY/AgRP neurones at the level of the ARC. 4. The effects of feeding-related signals on hypothalamic neuropeptide expression were investigated using real-time-PCR. A new protocol measuring gene expression from hypothalamic explants was developed. Effects of GABA and AMPA on c-fos expression were investigated and subsequent studies showed leptin and glucose modulated the expression of NPY, POMC and AgRP, in fed and fasted animals. Further work is required to validate this novel approach to studying the central control of energy balance.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry Q Science > QM Human anatomy
Library of Congress Subject Headings (LCSH):	Hypothalamus -- Research, Electrophysiology -- Research, Glucose -- Physiological effect, Serotoninergic mechanisms, Metabolism -- Regulation, Polymerase chain reaction
Date:	September 2008
Institution:	University of Warwick
Theses Department:	Warwick Medical School
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Spanswick, David
Sponsors:	Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC)
Format of File:	pdf
Extent:	xv, 315 leaves : ill. (some col.), charts
Language:	eng
URI:	http://wrap.warwick.ac.uk/id/eprint/3372

Request changes to a record

Actions (login required)

View Item