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Monoamine involvement in hippocampal self-stimulationVan der Kooy, Derek January 1977 (has links)
The roles of the noradrenergic and serotonergic innervations of the hippocampus were investigated with respect to their involvement in the intracranial self-stimulation of this structure. In the first study, 6-hydroxydopamine-induced lesions of the dorsal tegmental noradrenergic
bundle ascending to the forebrain had no effect on hippocampal self-stimulation in rats. In the second study, intragastric administration
of para-chlorophenylalanine decreased hippocampal self-stimulation, suggesting the importance of a serotonin input in maintaining this behavior. Identical para-chlorophenylalanine treatments resulted in temporary depletions of brain serotonin which paralleled the changes in hippocampal self-stimulation. The maximal decreases in both the biochemical
and behavioral measures occurred at 4 days' post-drug. Interpretations
of this deficit in hippocampal self-stimulation in terms of gross sensory and/or motor changes were ruled out, as animals with lateral hypothalamic electrodes showed increases in self-stimulation paralleling the post-drug serotonin changes. An intrasessional analysis of the para-chlorophenylalanine-induced behavioral changes revealed that lateral hypothalamic self-stimulation was facilitated mainly during the first hr of the 2 hr test sessions, whereas the depression in hippocampal
self-stimulation occurred primarily in the last hour of the sessions. The differential effects of para-chlorophenylalanine on lateral hypothalamic and hippocampal self-stimulation provide evidence against simple monoamine theories of reinforcement. / Arts, Faculty of / Psychology, Department of / Graduate
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Studies on the induction of short- and long-term synaptic potentiation in the hippocampusMay, Patrick B. Y. January 1987 (has links)
High frequency repetitive stimulation of an excitatory input in the hippocampus results in a post-tetanic potentiation (PTP) of short duration (about 3 min) that can be followed by a long-term synaptic potentiation (LTP) of the same excitatory input (Schwartzkroin and Wester, 1975; Andersen
et al., 1977). It has been reported that this tetanus-induced LTP cannot be
elicited in a Ca²⁺-free medium and is therefore a Ca²⁺-dependent process
(Dunwiddie et al., 1978; Dunwiddie and Lynch, 1979; Wigstrӧm et al., 1979).
Whether the induction of LTP is directly dependent upon Ca²⁺, or whether, Ca²⁺ is required because synaptic transmission is needed to initiate
certain postsynaptic process(es) (a postsynaptic depolarization, for
instance) leading to LTP, is unknown. Recent studies from this laboratory
showed that both short-term potentiation (STP; with a duration resembling
PTP) and LTP can be associatively induced if activation of a test input
co-occured with either a tetanic stimulation of separate excitatory inputs
or a sufficient depolarization of the postsynaptic neurone (Sastry et al.,
1985). In this study, experiments were performed to investigate (1) whether
associative STP could be induced when activation of the test input preceded
or followed the onset of the conditioning train and (2) whether LTP could be
induced in the absence of Ca²⁺ in the extracellular medium if sufficient depolarizations of the presynaptic terminals and postsynaptic neurones were provided.
All experiments were performed using the transversely sectioned hippocampal slice preparation. Test stimuli were delivered via an electrode located in the stratum radiatum while the conditioning tetani (100 Hz, 10 pulses per train) were delivered via another electrode located in the recorded from the apical dendritic area of CA₁ neurones. After the initial control stimulation period, 5 conditioning tetani were given at a frequency of 0.2 Hz. The test stimuli either preceded (-) or followed ( + ) the onset of each conditioning train by 0 to 100 ms. When the test stimulus followed the onset of each conditioning train, there was significant STP of the test EPSP up to a conditioning-test interval of +80 ms. When the test stimulus preceded the onset of each conditioning train, there was significant STP of the test EPSP up to a conditioning-test interval of -50 ms. Conditioning tetani that were given without co-activation of the test input resulted in a subsequent depression of the test EPSP. It is suggested that either the test or the conditioning input can initiate some postsynaptic process(es) which can in turn affect the activated presynaptic terminals to increase transmitter release or alter the subsynaptic dendritic properties.
For studying the possibility of the induction of LTP in the absence of
Ca²⁺ in the extracellular medium, population EPSPs were recorded from
apical dendritic area of CA₁ neurones in response to stratum radiatum
stimulation. After the control stimulation period, slices were exposed
either to Ca²⁺-containing or Ca²⁺-free (with Mn²⁺ and Mg²⁺ replacing
Ca²⁺) medium, with the concentration of KC1 at 10 to 80 mM. Long-term
potentiation of the population EPSPs was observed following the exposure to
high K⁺ in Ca²⁺-free media. Following a brief period of potentiation
initially, population EPSPs often exhibited a tendency toward depression
after exposure to high K⁺ in Ca²⁺-containing media. LTP induced by high
K⁺ in Ca²⁺-free medium could also be observed when a fixed number of axons were being activated, indicating that a recruitment of presynaptic fibres cannot entirely account for the potentiation. LTP of the depolarizing commands were paired with activation of the stratum radiatum
while the slices were exposed to Ca²⁺ -free medium (normal concentration of
KC1). These results suggest that extracellular Ca²⁺, synaptic transmission and thus subsynaptic receptor activation are not necessary for the induction of LTP as long as sufficient depolarizations of the presynaptic terminals and postsynaptic neurones are provided. / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate
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The roles of the hippocampus in recognition memoryWais, Peter Edward. January 2008 (has links)
Thesis (Ph. D.)--University of California, San Diego, 2008. / Title from first page of PDF file (viewed September 3, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 128-137).
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The Role of Chromatin Remodeling in Hippocampus in Depression and Antidepressant ActionTsankova, Nadejda Mincheva January 2008 (has links)
Dissertation (Ph.D.) -- University of Texas Southwestern Medical Center at Dallas, 2008. / Vita. Bibliography: p.184-192
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A single early life seizure permanently alters working memory, hippocampal plasticity and glutamate receptor localization /Cornejo, Brandon John. January 2006 (has links)
Thesis (Ph.D. in Pharmacology) -- University of Colorado, 2006. / Typescript. Includes bibliographical references (leaves 125-149). Free to UCDHSC affiliates. Online version available via ProQuest Digital Dissertations;
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Calcium regulation in long-term changes of neuronal excitability in the hippocampal formationMody, Istvan January 1985 (has links)
The regulation of calcium (Ca²⁺) was examined during long-term changes of neuronal excitability in the mammalian CNS. The preparations under investigation included the kindling model of epilepsy, a genetic form of epilepsy and long-term potentiation (LTP) of neuronal activity. The study also includes a discussion of the possible roles of a neuron-specific calcium-binding protein (CaBP). The findings are summarized as follows:
1) The distribution of CaBP was determined in cortical areas of the rat using a specific radioimmunoassay. The protein was found to have an unequal distribution in various cortical areas with preponderence in ventral structures.
2) Extending previous studies on the role of CaBP in kindling-induced epilepsy, its decline was correlated to the number of evoked afterdischarges (AD's) during the process of kindling.
3) Marked changes in CaBP levels were also found in the brains of the epileptic strain of mice (El). The hippocampal formation and the dorsal occipital cortex contained significantly lower CaBP than the control (CF-1) strain. The induction of seizures further decreased the levels of CaBP in the El mice. These findings are indicative of a possible genetic impairment of neuronal Ca²⁺ homeostasis in the El strain. 4) The levels of total hippocampal Ca²⁺ and Zn²⁺ were measured by atomic absorption spectrophotometry in control and commissural-kindled animals. While no change was found in the total Ca²⁺ content of the region, hippocampal Zn²⁺ of kindled preparations was found to be significantly elevated.
5) To measure Ca²⁺ -homeostasis, the kinetic analysis of ⁴⁵Ca uptake curves was undertaken in the in vitro hippocampus. This technique was found to be a valid method for assessment of Ca²⁺-regulation in the CNS under both physiological and pathophysiological conditions. The effect of various extracellular Ca²⁺ concentrations, 2,3-dinitrophenol (DNP), calcitonin, nifedipine and 3-isobutyl-1-methylxanthine (IBMX) on ⁴⁵Ca uptake curves was examined in order to identify the two exchangeable Ca²⁺ pools derived through kinetic analysis.
6) The kinetic analysis of ⁴⁵Ca uptake curves revealed that Ca²⁺-regulation of the hippocampus is impaired following amygdala- and commissural kindling. The changes reflect an enhancement of a Ca²⁺ pool that includes free cytosolic Ca²⁺ and a concomitant decrease in the amount of buffered calcium probably as a result in the decrease of hippocampal CaBP levels.
7) A novel form of long-term potentiation (LTP) of neuronal activity in the CA1 region of the hippocampus is described. Perfusion of 100 uM of IBMX in the hippocampal slice preparation induced a long lasting increase in the amplitude of the stratum radiatum evoked population spike and EPSP responses with changes in synaptic efficacy as indicated by the altered input/output relationships. Intracellular correlates of IBMX-induced LTP included lowering of synaptic threshold and enhancement of the rate of rise of the EPSP with no alterations in the passive membrane characteristics of CA1 pyramidal neurons. The fact that IBMX was able to exert its effect even in the presence of the calcium-blocker cation Co²⁺, taken together with the drug's action on hippocampal exchangeable Ca²⁺, raises the possibility that the Ca²⁺ necessary for induction of LTP may be derived from an intraneuronal storage site.
These studies indicate the significance of intracellular Ca²⁺ -regulatory mechanisms in long-term changes of neuronal excitability which occur in experimental models of epilepsy and long-term potentiation. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate
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Changes in the cell surface-distribution of ionotrophic glutamate receptors during development, receptor trafficking and synaptic plasticity in cultured hippocampal neuronsPickard, Lisa Andrea January 2001 (has links)
No description available.
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Electrophysiological studies of synaptic function in different regions of the hippocampusRadpour, Shahrzad January 1989 (has links)
No description available.
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A study of the changes in dentate granule cell excitability and inhibition in the kainic acid model of temporal lobe epilepsyBarrow, Paul Anthony January 1997 (has links)
No description available.
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Cytoarchitecture and connectional organization in the telencephalic medial wall of the domestic chick (Gallus domesticus)Pisana, M. January 1986 (has links)
No description available.
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