Beteiligte:
Sernagor, Evelyne;
Grzywacz, Norberto M.
Erschienen:
Society for Neuroscience, 1999
Erschienen in:The Journal of Neuroscience
Sprache:
Englisch
DOI:
10.1523/jneurosci.19-10-03874.1999
ISSN:
0270-6474;
1529-2401
Entstehung:
Anmerkungen:
Beschreibung:
<jats:p>Extracellular recordings were obtained from the ganglion cell (GC) layer during correlated spontaneous bursting activity (SBA) in the immature turtle retina. Pharmacological agents were bath-applied, and their effects on burst and correlation parameters were determined.</jats:p><jats:p>SBA requires synaptic transmission. It was blocked in the presence of curare and mecamylamine, two cholinergic nicotinic antagonists, and enhanced with neostigmine, a cholinesterase inhibitor. SBA was profoundly inhibited during blockade of glutamatergic receptors with the broad spectrum antagonist kynurenate and it vanished with 6,7-dinitroquinoxaline-2–3-dione (DNQX) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), two AMPA/kainate receptor antagonists. Blockade of NMDA receptors with<jats:sc>d</jats:sc>(−)-2-amino-5-phosphonopentanoic acid (<jats:sc>d</jats:sc>-AP-5) led only to a modest reduction in SBA. Blockade of GABA<jats:sub>A</jats:sub>receptors with bicuculline prolonged the duration of the bursts. Inhibition of GABA uptake with nipecotic acid led to a decrease in burst rate. Blockade of K<jats:sup>+</jats:sup>channels with cesium (Cs<jats:sup>+</jats:sup>) and tetraethylammonium (TEA) led to a dramatic decrease in excitability. Burst propagation between neighboring GCs was reduced by K<jats:sup>+</jats:sup>channel blockade. Gap junction blockade had no consistent effect on bursts or correlation parameters. None of these drugs had a strong effect on the refractory period between bursts.</jats:p><jats:p>We conclude that correlated SBA in immature turtle GCs requires both cholinergic nicotinic and glutamatergic (mainly through AMPA/kainate receptors) synaptic transmission. GABAergic activity modulates the intensity and the duration of the bursts. Extracellular K<jats:sup>+</jats:sup>is involved in lateral activity propagation and increases retinal excitability, which may be required for burst generation.</jats:p>