Information processing in the vertebrate retina occurs two separate channels known as ON and OFF channels. When intracellular electrophysiological recordings were obtained from perfused retina-eyecup preparation of mudpuppy ( Necturus maculosus ), addition 2-amino-4-phosphonobutyric acid to bathing medium blocked all responses channel but left intact including ganglion cell discharge. 2-Amino-4-phosphonobutyric blocks light response bipolar by mimicking endogenous photoreceptor transmitter.

Light-evoked intraretinal field potentials (electroretinogram, ERG) have been measured simultaneously with extracellular potassium fluxes in the amphibian retina. The application of highly selective pharmacologic agents permitted us to functionally isolate various classes retinal neurons. It was found that: (a) APB (2-amino-4-phosphonobutyrate), which has previously shown selectively abolish light responsiveness ON bipolar cells, causes a concomitant loss ERG b-wave and flux. (b) Conversely,...

Phasic and tonic light responses provide a fundamental division of visual information that is thought to originate in the inner retina. However, evidence presented here indicates this duality originates outer In response steady stimulus, temporal On-bipolar cells fell into two groups. one group, peaked then rapidly declined (τ ∼ 400 msec) close resting membrane potential. At offset, these exhibited transient afterhyperpolarization. second group cells, 10-fold more slowly reached...

cis -2,3-Piperidinedicarboxylic acid (PDA), an excitatory amino antagonist, reversibly blocked cone input to OFF bipolars and horizontal cells, whereas ON were relatively unaffected. Kainic effects also blocked, indicating a postsynaptic mechanism of action. The use PDA helps characterize one two classes synaptic receptors that mediate influence in the outer retina.

As with other retinal cell types, ganglion cells (RGCs) arise from multipotent progenitor (RPCs), and their formation is regulated by a hierarchical gene-regulatory network (GRN). Within this GRN, three transcription factors--atonal homolog 7 (Atoh7), POU domain, class 4, factor 2 (Pou4f2), insulin gene enhancer protein 1 (Isl1)--occupy key node positions at two different stages of RGC development. Atoh7 upstream required for RPCs to gain competence an fate, whereas Pou4f2 Isl1 are...

Abstract Whole-cell voltage clamp in the retinal slice and intracellular current intact retina were used to study inhibitory interactions inner plexiform layer. Picrotoxin or strychnine reduced inhibitory, light-evoked currents a majority of ganglion cells. However, nearly third cells, each these antagonists enhanced synaptic current. All was blocked by addition other antagonist. This indicates cross-inhibition between GABAergic glycinergic feedforward pathways. Blocking GABA A Rs with...

Large-conductance calcium-activated potassium (BK) channels are colocalized with calcium at sites of exocytosis the presynaptic terminals throughout nervous system. It is expected that their activation would provide negative feedback to transmitter release, but opposite sometimes observed. Attempts resolve this apparent paradox based on alterations in action potential waveform have been ambiguous. In an alternative approach, we investigated influence channel neurotransmitter release a...

Retinal rod photoreceptors are depolarized in darkness to approximately −40 mV, a state which they maintain sustained glutamate release despite low levels of calcium channel activation. Blocking voltage-gated channels or ryanodine receptors (RyRs) at the presynaptic terminal suppressed synaptic communication bipolar cells. Spontaneous events were also inhibited when either these pathways was blocked. This indicates that both influx and from internal stores required for normal transmitter...

Synaptic signals from retinal bipolar cells were monitored by measuring EPSCs in ganglion voltage-clamped at -70 mV. Spontaneous strongly suppressed l-2-amino-4-phosphonobutyrate (AP-4), an agonist group III metabotropic glutamate receptors (mGluRs). Agonists of I or II mGluRs ineffective. AP-4 also cell evoked stimulation using potassium puffs, sucrose zaps current (0.5-1 microA). In addition, Off dim-light stimuli. This indicates that mediate a direct suppression transmitter release. An...

Glycinergic and GABAergic inhibition are juxtaposed at one retinal synaptic layer yet likely perform different functions. These functions have usually been evaluated using receptor antagonists. In examining glycine receptors, we were surprised to find that commonly used concentrations of GABA antagonists blocked significant fractions the current. amacrine ganglion cells, competitive GABAA (bicuculline SR95531) also GlyR Picrotoxinin produced a noncompetitive GlyRs....

1. Electrophysiological recordings were obtained from neurons in the amphibian intact retina and retinal slice preparations. The effects of gamma-aminobutyric acid (GABA) evaluated presence bicuculline or SR95531, which block GABAA receptor, baclofen, saturates GABAB receptor. 2. Under these conditions, GABA preferentially reduced ON light responses amacrine ganglion cells, apparently through a presynaptic mechanism that bipolar cell input. also produced small hyperpolarization resting...

1. Baclofen, a gamma-aminobutyric acid (GABA)/B receptor agonist, was bath applied while recording the responses of second- and third-order neurons in mudpuppy retina. Baclofen receptors were largely restricted to amacrine ganglion cells. 2. hyperpolarized membrane potential many, but not all, neurons. This involved an increase input conductance, probably associated with opening potassium channels. 3. The maximal conductance activation GABA/B approximately one-third that produced by GABA/A...

1. Whole-cell voltage clamp experiments were performed on isolated spiking retinal neurons from the salamander retina. Calcium channel currents studied using barium as charge carrier while potassium and sodium suppressed with TEA TTX, respectively. 2. Baclofen, a metabotropic GABA receptor agonist, both enhanced high-voltage-activated calcium current. Baclofen facilitated an L-type current, this effect was not dependent. As reported previously, baclofen inhibited N-type current action 3....

Metabotropic γ-aminobutyric acid (GABA) receptors were studied in amphibian retinal ganglion cells using whole cell current and voltage clamp techniques. The aim was to identify the types of receptor present their mechanisms action modulation. Previous results indicated that possess two ionotropic GABA receptors: GABAAR GABACR. This study demonstrates they also metabotropic GABAB receptor: one sensitive baclofen another cis-aminocrotonic (CACA). effects these selective agonists blocked by...

Glutamate suppressed high‐voltage‐activated barium currents (I Ba,HVA ) in tiger salamander retinal ganglion cells. Both ionotropic (iGluR) and metabotropic (mGluR) receptors contributed to this calcium channel inhibition. Trans ‐ACPD (1‐aminocyclopentane‐ trans ‐1 S ,3 R ‐dicarboxylic acid), a broad‐spectrum glutamate receptor agonist, dihydropyridine‐sensitive current. Kainate, an reduced ω‐conotoxin GVIA‐sensitive The relative effectiveness of selective agonists indicated that the...

The neuronal generators of the b- and d-waves electroretinogram (ERG) were investigated in tiger salamander retina to determine if amacrine ganglion cells contribute this field potential. Several agents used that affect third-order neurons, such as tetrodotoxin, baclofen, NMDA agonists antagonists. Baclofen, an agent enhances light responses increased d-wave reduced b-wave. In contrast, decrease neurons had opposite effect enhancing b-wave depressing d-wave. on was particularly pronounced....

The synaptic output of retinal bipolar cells was monitored by recording light-evoked EPSCs in ganglion cells. Application (RS)-2-amino-3-(3-hydroxy-5-tert-butyl-4-isoxazolyl (ATPA), a selective agonist at kainate receptors, depolarized amacrine and reduced the excitatory current (L-EPSC) ATPA had only slight effect on light responses Therefore, suppresses cell to transient L-EPSC, but comparatively little sustained ON L-EPSC more suppressed than OFF L-EPSC. Thus, preferentially from...