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Short-term plasticity in excitatory synapses of the rat medial preoptic nucleus.
Umeå University, Faculty of Medicine, Integrative Medical Biology, Physiology.
Umeå University, Faculty of Medicine, Integrative Medical Biology, Physiology.
Umeå University, Faculty of Medicine, Integrative Medical Biology, Physiology.
2006 (English)In: Brain Research, ISSN 0006-8993, Vol. 1110, no 1, 128-35 p.Article in journal (Refereed) Published
Abstract [en]

The medial preoptic nucleus (MPN) regulates sexual behavior which is subject to experience-dependent modifications. Such modifications must depend on functional plasticity in the controlling neural circuits. Thus, MPN synapses are likely candidates for the site of alterations. The present work is a first systematic study of functional synaptic plasticity at glutamatergic synapses in the MPN. Short-term activity-dependent plasticity was investigated using a slice preparation from young male rats. The average efficacy of AMPA/kainate-receptor-mediated synaptic transmission was activity-dependent, showing a peak at a steady stimulation rate of 2 Hz. The variation in efficacy was attributed to mainly presynaptic factors since the average response amplitude was roughly paralleled by the response probability. Upon paired-pulse stimulation, paired-pulse facilitation as well as paired-pulse depression was observed. In some cases, paired-pulse facilitation as well as paired-pulse depression was recorded from an individual neuron depending on the interval between the paired stimuli. On average, paired-pulse facilitation was observed at intervals <500 ms, and paired-pulse depression at intervals in the range 1-4 s. The findings thus reveal complex activity-dependent short-term plasticity of the functional synaptic properties in the medial preoptic nucleus.

Place, publisher, year, edition, pages
2006. Vol. 1110, no 1, 128-35 p.
Keyword [en]
Animals, Dose-Response Relationship; Radiation, Electric Stimulation/methods, Excitatory Postsynaptic Potentials/*physiology/radiation effects, Neuronal Plasticity/*physiology, Preoptic Area/*cytology, Rats, Rats; Sprague-Dawley, Synapses/*physiology, Time Factors
URN: urn:nbn:se:umu:diva-12593DOI: doi:10.1016/j.brainres.2006.06.061PubMedID: 16870159OAI: diva2:152264
Available from: 2008-01-11 Created: 2008-01-11 Last updated: 2011-01-11Bibliographically approved
In thesis
1. Neurotransmission and functional synaptic plasticity in the rat medial preoptic nucleus
Open this publication in new window or tab >>Neurotransmission and functional synaptic plasticity in the rat medial preoptic nucleus
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Brain function implies complex information processing in neuronal circuits, critically dependent on the molecular machinery that enables signal transmission across synaptic contacts between neurons. The types of ion channels and receptors in the neuronal membranes vary with neuron types and brain regions and determine whether neuronal responses will be excitatory or inhibitory and often allow for functional synaptic plasticity which is thought to be the basis for much of the adaptability of the nervous system and for our ability to learn and store memories. The present thesis is a study of synaptic transmission in the medial preoptic nucleus (MPN), a regulatory center for several homeostatic functions but with most clearly established roles in reproductive behaviour. The latter behaviour typically shows several distinct phases with dramatically varying neuronal impulse activity and is also subject to experience-dependent modifications. It seems likely that the synapses in the MPN contribute to the behaviour by means of activity-dependent functional plasticity. Synaptic transmission in the MPN, however, has not been extensively studied and is not well understood. The present work was initiated to clarify the synaptic properties in the MPN. The aim was to achieve a better understanding of the functional properties of the MPN, but also to obtain information on the functional roles of ion channel types for neurotransmission and its plastic properties in general. The studies were carried out using a brain slice preparation from rat as well as acutely isolated neurons with adhering nerve terminals. Presynaptic nerve fibres were stimulated electrically or, in a few cases, by raised external K+ concentration, and postsynaptic responses were recorded by tight-seal perforated-patch techniques, often combined with voltage-clamp control of the post-synaptic membrane potential. Glutamate receptors of α-amino-3-hydroxy-5-methyl-4-izoxazole propionic acid (AMPA) and N-methyl-D-aspartate (NMDA) types were identified as mediating the main excitatory synaptic signals and γ-aminobutyric acid (GABA)A receptors as mediating the main inhibitory signals. Both types of signals were suppressed by serotonin. The efficacy of AMPA-receptor-mediated transmission displayed several types of short-term plasticity, including paired-pulse potentiation and paired-pulse depression, depending on the stimulus rate and pattern. The observed plasticity was attributed to mainly presynaptic mechanisms. To clarify some of the presynaptic factors controlling synaptic efficacy, the role of presynaptic L-type Ca2+ channels, usually assumed not to directly control transmitter release, was investigated. The analysis showed that (i) L-type channels are present in GABA-containing presynaptic terminals on MPN neurons, (ii) that these channels provide a means for differential control of spontaneous and impulse-evoked GABA release and (iii) that this differential control is prominent during short-term synaptic plasticity. A model where Ca2+ influx through L-type channels may lead to reduced GABA release via effects on Ca2+-activated K+ channels, membrane potential and other Ca2+-channel types explains the observed findings. In addition, massive Ca2+ influx through L-type channels during high-frequency stimulation may contribute to increased GABA release during post-tetanic potentiation. In conclusion, the findings obtained in the present study indicate that complex neurotransmission mechanisms and different forms of synaptic plasticity contribute to the specific functional properties of the MPN.

Place, publisher, year, edition, pages
Umeå: IMB, 2009. 57 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1286
medial preoptic nucleus, synaptic plasticity, GABA, glutamate, L-type Ca2+ channel
National Category
Research subject
urn:nbn:se:umu:diva-25874 (URN)978-91-7264-843-2 (ISBN)
Fysiologi, 901 87, Umeå
Public defence
2009-09-30, Hörsal KB3A9, Umeå Universitet, Umeå, 10:00 (English)
Available from: 2009-09-10 Created: 2009-09-08 Last updated: 2010-01-18Bibliographically approved

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