We studied feedback from horizontal cells to cones in isolated goldfish retinae and found that surround stimuli evoke an inward current and a slowly developing outward current. The surround-evoked currents are blocked by the glutamate antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) and are, like horizontal cell responses, most effectively evoked by large stimuli. This indicates that the curr...

Spreading depression (SD) as well as hypoxia-induced SD-like depolarization in forebrain gray matter are characterized by near complete depolarization of neurons. The biophysical mechanism of the depolarization is not known. Earlier we reported that simultaneous pharmacological blockade of all known major Na(+) and Ca(2+) channels prevents hypoxic SD. We now recorded extracellular voltage, Na(+...

Spontaneous and light-evoked postsynaptic currents (sPSCs and lePSCs, respectively) in retinal ganglion cells of the larval tiger salamander were recorded under voltage-clamp conditions from living retinal slices. The focus of this study is to characterize the spontaneous inhibitory PSCs (sIPSCs) and their contribution to the light-evoked inhibitory PSCs (leIPSCs) in ON-OFF ganglion cells. sIPS...

Removal of the superior colliculus (SC) in neonatal Wistar rats results in a rapid loss of retinal ganglion cells (RGCs). There is an early twofold increase in RGC death 4-8 hr postlesion (PL) followed by a later 10-11-fold increase in pyknosis about 24 hr PL. We have now used neurotrophic factors (BDNF, NT-4/5, NT-3, NGF, LIF), glutamate receptor antagonists (MK-801, DNQX, CNQX), an antioxidan...

Guanine nucleotides behave as competitive antagonists at ionotropic glutamate receptors and show neuroprotective activity in different experimental excitotoxicity paradigms, both in vivo and in cultured cell preparations. Taking 5'-GMP as the reference nucleotide, we have tried to understand how these molecules interact with the agonist-binding site of the GluR2 alpha-amino-3-hydroxy-5-methyl-4...

Light-evoked currents in depolarizing and hyperpolarizing bipolar cells (DBCs and HBCs) were recorded under voltage-clamp conditions in living retinal slices of the larval tiger salamander. Responses to illumination at the center of the DBCs' and HBCs' receptive fields were mediated by two postsynaptic currents: DeltaI(C), a glutamate-gated cation current with a reversal potential near 0 mV, an...

We investigated whether entorhinal cortex (EC) layer IV neurons are hyperexcitable in the post-selfsustaining limbic status epilepticus (post-SSLSE) animal model of temporal lobe epilepsy. We studied naive rats (n = 44), epileptic rats that had experienced SSLSE resulting in spontaneous seizures (n = 45), and electrode controls (n = 7). There were no differences between electrode control and na...

Although the epileptogenic properties of estrogens have been widely demonstrated in several models and species, the mechanism(s) by which estrogens can acutely change seizure parameters including after discharge and seizure duration remain remains to be determined. In the present study, we examined the role of NMDA (N-methyl-D-aspartate), non-NMDA and estrogenic receptors in estradiol benzoate ...

BACKGROUND Direct delivery of drugs and other agents into the inner ear will be important for many emerging therapies, including the treatment of degenerative disorders and guiding regeneration. METHODS We have taken a microfluidics/MEMS (MicroElectroMechanical Systems) technology approach to develop a fully implantable reciprocating inner-ear drug-delivery system capable of timed and sequenc...

The effects of gonadal steroid hormones on dendritic spines were studied in hippocampal neurons that were dissociated and grown in culture for 2-3 weeks. Exposure to estradiol caused up to a twofold increase in dendritic spine density in these neurons. The effect of estradiol was stereospecific and blocked by the steroid antagonist tamoxifen. The estradiol-induced rise in spine density was bloc...