Uwe Heinemann

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We provide physiological, pharmacological, and structural evidence that axons of hippocampal principal cells are electrically coupled, with prepotentials or spikelets forming the physiological substrate of electrical coupling as observed in cell somata. Antidromic activation of neighboring axons induced somatic spikelet potentials in neurons of CA3, CA1,(More)
The effect of low extracellular Mg2+ concentration ([Mg2+]o) on neuronal activity was studied in rat hippocampal slices. After 20-40 min of perfusion with Mg2+-free medium, when [Mg2+]o declined to approximately 0.1-0.4 mM, spontaneous field potentials developed in the CA1 and CA3 regions, but not in the dentate gyrus. In the CA3 pyramidal cell layer, these(More)
Astrocytic gap junctions have been suggested to contribute to spatial buffering of potassium in the brain. Direct evidence has been difficult to gather because of the lack of astrocyte-specific gap junction blockers. We obtained mice with coupling-deficient astrocytes by crossing conditional connexin43-deficient mice with connexin30(-/-) mice. Similar to(More)
Extracellular calcium and potassium activities (aCa and aK) as well as neuronal activity were simultaneously recorded with ion-sensitive electrodes in the somatosensory cortex of cats. Baseline aCa was 1.2–1.5 mM/1, baseline a k 2.7–3.2 mM/1. Transient decreases in aCa and simultaneous increases in aK were evoked by repetitive stimulation of the(More)
Hippocampal sharp wave–ripple complexes (SPW-Rs) occur during slow-wave sleep and behavioral immobility and are thought to represent stored information that is transferred to the neocortex during memory consolidation. Here we show that stimuli that induce long-term potentiation (LTP), a neurophysiological correlate of learning and memory, can lead to the(More)
1. The perforant path projection from layer III of the entorhinal cortex to CA1 of the hippocampus was studied within a hippocampal-entorhinal combined slice preparation. We prevented contamination from the other main hippocampal pathways by removal of CA3 and the dentate gyrus. 2. Initially the projection was mapped using field potential recordings that(More)
The role of extracellular K+ (K+o) in nonsynaptic epileptogenesis induced in the CA1 area of rat hippocampal slices by lowering [Ca2]o was studied with K+-selective microelectrodes (KSMs). Extracellular field potentials and [K+]o were recorded simultaneously with 1-2 KSMs in the CA1 stratum pyramidale. In slices perfused with an oxygenated standard(More)
As a structure involved in learning and memory, the hippocampus functions as a network. The functional differentiation along the longitudinal axis of the hippocampus is poorly demarcated in comparison with the transverse axis. Using patch clamp recordings in conjunction with post hoc anatomy, we have examined the pattern of connectivity and the functional(More)
It has long been recognized that insults to the cerebral cortex, such as trauma, ischaemia or infections, may result in the development of epilepsy, one of the most common neurological disorders. Human and animal studies have suggested that perturbations in neurovascular integrity and breakdown of the blood-brain barrier (BBB) lead to neuronal(More)
Neurones generate intrinsic subthreshold membrane potential oscillations (MPOs) under various physiological and behavioural conditions. These oscillations influence neural responses and coding properties on many levels. On the single-cell level, MPOs modulate the temporal precision of action potentials; they also have a pronounced impact on large-scale(More)