Search results for "hippocampus"
showing 10 items of 622 documents
Stimulation of hippocampal acetylcholine release by hyperforin, a constituent of St. John’s Wort
2004
Abstract Extracts of the medicinal plant St. John’s Wort ( Hypericum perforatum ) are widely used in the therapy of affective disorders and have been reported to exert antidepressant, anxiolytic, and cognitive effects in experimental and clinical studies. We here report that hyperforin, the major active constituent of the extract, increases the release of acetylcholine from rat hippocampus in vivo as determined by microdialysis. Hippocampal acetylcholine levels were increased by 50–100% following the systemic administration of pure hyperforin at doses of 1 and 10 mg/kg. The effect was almost completely suppressed by local perfusion with calcium-free buffer or with tetrodotoxin (1 μM). We co…
A Critical Period for Prefrontal Network Configurations Underlying Psychiatric Disorders and Addiction
2020
The medial prefrontal cortex (mPFC) has been classically defined as the brain region responsible for higher cognitive functions, including the decision-making process. Ample information has been gathered during the last 40 years in an attempt to understand how it works. We now know extensively about the connectivity of this region and its relationship with neuromodulatory ascending projection areas, such as the dorsal raphe nucleus (DRN) or the ventral tegmental area (VTA). Both areas are well-known regulators of the reward-based decision-making process and hence likely to be involved in processes like evidence integration, impulsivity or addiction biology, but also in helping us to predict…
Detecting global and local hippocampal shape changes in Alzheimer's disease using statistical shape models.
2012
Item does not contain fulltext The hippocampus is affected at an early stage in the development of Alzheimer's disease (AD). With the use of structural magnetic resonance (MR) imaging, we can investigate the effect of AD on the morphology of the hippocampus. The hippocampal shape variations among a population can be usually described using statistical shape models (SSMs). Conventional SSMs model the modes of variations among the population via principal component analysis (PCA). Although these modes are representative of variations within the training data, they are not necessarily discriminative on labeled data or relevant to the differences between the subpopulations. We use the shape des…
Unusual target selectivity of perisomatic inhibitory cells in the hilar region of the rat hippocampus.
2000
Perisomatic inhibitory innervation of all neuron types profoundly affects their firing characteristics and vulnerability. In this study we examined the postsynaptic targets of perisomatic inhibitory cells in the hilar region of the dentate gyrus where the proportion of potential target cells (excitatory mossy cells and inhibitory interneurons) is approximately equal. Both cholecystokinin (CCK)- and parvalbumin-immunoreactive basket cells formed multiple contacts on the somata and proximal dendrites of mossy cells. Unexpectedly, however, perisomatic inhibitory terminals arriving from these cell types largely ignored hilar GABAergic cell populations. Eighty-ninety percent of various GABAergic…
Strain-specific development of the mossy fiber system in organotypic cultures of the mouse hippocampus
1988
Abstract The postnatal development of the hippocampus of the inbred mice strains BALB/c, C57BL/6, and DBA/2 was studied in organotypic explant cultures using the roller-tube technique. In vivo, mice exhibit strain-specific mossy fiber distribution patterns. As a main result we found, that after cultivation of 3–4 weeks, similar strain-specific patterns became apparent in vitro, as visualized by a modified Timm staining. From this experiment we can conclude that a postnatal extrinsic influence cannot be the cause of the strain-specific hippocampal features.
Zinc-positive presynaptic boutons of the rabbit hippocampus during early postnatal development
1998
Abstract The evolution of vesicular zinc-containing boutons in the developing rabbit hippocampus has been studied during early postnatal life using the selenite–Danscher histochemical method. By P3, large immature mossy fiber boutons with labeled synaptic vesicles were seen in the hilus of the dentate gyrus and in the stratum lucidum of the CA3–CA4 hippocampal areas. After P5, smaller boutons with labeled vesicles were identified in the stratum oriens and stratum radiatum of all hippocampal areas, and even transiently in the stratum lacunosum of P6 animals. Vesicular zinc-containing boutons increased in number and underwent ultrastructural maturation; light microscope densitometric–volumetr…
Immunohistochemical analysis of KCNQ2 potassium channels in adult and developing mouse brain
2005
The syndrome of benign familial neonatal convulsions (BFNC) is characterized by seizures starting within the first days of life and disappearing within weeks to months. BFNC is caused by loss-of-function mutations in the potassium channels KCNQ2 and KCNQ3 which can well explain the resulting neuronal hyperexcitability. However, it is not understood why seizures predominantly occur in the neonatal period. A potential explanation might be a change in the expression pattern of these channels during development. We therefore performed an immunohistochemical analysis of mouse brain slices at different stages of postnatal development using an antibody recognizing the C-terminus of the KCNQ2 chann…
Behavioral and hippocampal evoked responses in an auditory oddball situation when an unconditioned stimulus is paired with deviant tones in the cat: …
1995
Event-related potentials (ERP) in the areas CA1, CA3 and dentate fascia (Df) of the hippocampal formation were recorded during an oddball situation in the cat. A rewarding electrical stimulation of the lateral hypothalamus (US) was paired with deviant tones (2500 Hz) that occurred randomly in a series of the standard tones (2000 Hz) given to the left ear. In addition to developing orienting head movements to the side of the deviant tones, an increase in the amplitude of parallel hippocampal ERPs was observed. Both the behavioral and neural responses appeared not until a 50 ms latency range. Furthermore, time-amplitude characteristics of the ERPs corresponded to time-acceleration characteris…
Dendritic Ih selectively blocks temporal summation of unsynchronized distal inputs in CA1 pyramidal neurons.
2004
The active dendritic conductances shape the input-output properties of many principal neurons in different brain regions, and the various ways in which they regulate neuronal excitability need to be investigated to better understand their functional consequences. Using a realistic model of a hippocampal CA1 pyramidal neuron, we show a major role for the hyperpolarization-activated current, I-h, in regulating the spike probability of a neuron when independent synaptic inputs are activated with different degrees of synchronization and at different distances from the soma. The results allowed us to make the experimentally testable prediction that the I-h in these neurons is needed to reduce ne…
Action of anticonvulsants on hippocampal slices in Mg-free medium
1989
The effects of six prototype anticonvulsant drugs were investigated on epileptiform field potential discharges evoked in hippocampal slices of rats by removing magnesium ions from the perfusion fluid in order to reveal a possible interaction with N-methyl-D-aspartate (NMDA) receptor activation. All drugs reduced the multiple discharges with the following order of potency: midazolam greater than carbamazepine = phenytoin = phenobarbital greater than ethosuximide = valproate. They had a stronger depressant effect on the later population spikes but none of them abolished the epileptiform discharge. These effects can be explained by known mechanisms of action of the anticonvulsants tested and l…