These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: APB suppresses synaptic input to retinal horizontal cells in fish: a direct action on horizontal cells modulated by intracellular pH.
    Author: Takahashi K, Copenhagen DR.
    Journal: J Neurophysiol; 1992 Jun; 67(6):1633-42. PubMed ID: 1352805.
    Abstract:
    1. Membrane potentials and cone-driven light responses were recorded from the H1-type horizontal cells in isolated retinas. Membrane potentials and intracellular pH were recorded also in enzymatically dissociated solitary horizontal cells. 2. In isolated retinas the glutamate analogue 2-amino-4-phosphonobutyrate (APB) hyperpolarized horizontal cells and reduced their light responses in a dose-dependent manner (5-200 microM). 3. The action of APB depended on the formulation of the saline; APB was effective in L-15 saline buffered with N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) but not in a commonly used, nominally CO2-free bicarbonate/Tris-buffered saline. 4. The major factor controlling the potency of APB was intracellular pH. APB was ineffective during retinal perfusion with NH4Cl-containing or CO2-free bicarbonate saline, both of which are known to alkalinize cells. In contrast, APB was effective in salines formulated to acidify the retinal neurons. These included both HEPES and Tris-buffered salines containing a weak acid and bicarbonate/Tris-buffered saline gassed with CO2. 5. APB reduced the size of glutamate-evoked depolarizations in solitary horizontal cells but had no independent action in the absence of glutamate. This reduction of glutamate-induced depolarization was observed in salines formulated to block voltage-dependent calcium and potassium currents. 6. The magnitude of APB's antagonistic action on solitary horizontal cells increased in a dose-dependent manner from 10 to 200 microM. The antagonism was increased by intracellular acidification and was reduced or eliminated by alkalinization. 7. We conclude that APB can reduce glutamate-evoked and, by inference, the photoreceptor neurotransmitter-evoked depolarization of horizontal cells by acting directly on the horizontal cells. This effect of APB is modulated by intracellular pH.
    [Abstract] [Full Text] [Related] [New Search]