Biomaterial Database

Synaptic feedback excitation has hypothalamic neural networks generate quasirhythmic burst activity. 1995

W Müller, and D Swandulla

Max-Planck-Institut für Biophysikalische Chemie, Abt. Membranbiophysik, AG Zellphysiologie, Göttingen, Germany.

1. Dissociated neurons from embryonic rat hypothalamus form synaptically coupled networks when cultured for several weeks. When synaptic inhibition is suppressed by the gamma-aminobutyric acid-A (GABAA) antagonist picrotoxin, neurons exhibit "rhythmic" burst activity that is blocked by the glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). 2. We have examined whether this type of activity is generated by pacemaker cells driving follower cells synaptically or whether it is generated by a neuronal network through feedback excitation by Ca2+ imaging of Fura-2/AM-loaded neurons and single-cell recording. 3. IN the presence of the GABAA antagonist picrotoxin (20 microM), a large majority of neurons (> 85%) displayed quasirhythmic increases in intracellular concentration of Ca2+ ([Ca2+]i). Single-cell recording revealed that these increases in [Ca2+]i correspond to burst discharges in individual neurons. When excitatory synaptic transmission was blocked by CNQX (20 microM), none of the imaged neurons exhibited significant oscillations in [Ca2+]i. 4. Investigation of the intervals between bursts from single-cell recording revealed a random distribution over a range of 400% from the minimum interval. Poincaré maps of burst intervals, i.e., graphs of all burst intervals versus their preceding burst interval, revealed that a burst interval is unpredictable from its predecessor. 5. When synaptic coupling was attenuated by low concentrations of CNQX (50-500 nM), the mean burst interval was considerably increased without a change in the random character of burst activity. 4-Aminopyridine (1 mM), known to increase synaptic efficiency, reduced the mean burst interval.(ABSTRACT TRUNCATED AT 250 WORDS)

UI	MeSH Term	Description	Entries
D007031	Hypothalamus	Ventral part of the DIENCEPHALON extending from the region of the OPTIC CHIASM to the caudal border of the MAMMILLARY BODIES and forming the inferior and lateral walls of the THIRD VENTRICLE.	Lamina Terminalis,Preoptico-Hypothalamic Area,Area, Preoptico-Hypothalamic,Areas, Preoptico-Hypothalamic,Preoptico Hypothalamic Area,Preoptico-Hypothalamic Areas
D007425	Intracellular Membranes	Thin structures that encapsulate subcellular structures or ORGANELLES in EUKARYOTIC CELLS. They include a variety of membranes associated with the CELL NUCLEUS; the MITOCHONDRIA; the GOLGI APPARATUS; the ENDOPLASMIC RETICULUM; LYSOSOMES; PLASTIDS; and VACUOLES.	Membranes, Intracellular,Intracellular Membrane,Membrane, Intracellular
D009415	Nerve Net	A meshlike structure composed of interconnecting nerve cells that are separated at the synaptic junction or joined to one another by cytoplasmic processes. In invertebrates, for example, the nerve net allows nerve impulses to spread over a wide area of the net because synapses can pass information in any direction.	Neural Networks (Anatomic),Nerve Nets,Net, Nerve,Nets, Nerve,Network, Neural (Anatomic),Networks, Neural (Anatomic),Neural Network (Anatomic)
D009994	Osmolar Concentration	The concentration of osmotically active particles in solution expressed in terms of osmoles of solute per liter of solution. Osmolality is expressed in terms of osmoles of solute per kilogram of solvent.	Ionic Strength,Osmolality,Osmolarity,Concentration, Osmolar,Concentrations, Osmolar,Ionic Strengths,Osmolalities,Osmolar Concentrations,Osmolarities,Strength, Ionic,Strengths, Ionic
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D004594	Electrophysiology	The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
D005246	Feedback	A mechanism of communication within a system in that the input signal generates an output response which returns to influence the continued activity or productivity of that system.	Feedbacks
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D013569	Synapses	Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.	Synapse
D017208	Rats, Wistar	A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.	Wistar Rat,Rat, Wistar,Wistar Rats