Zmj. Zhou et al., THE EXCITATORY AND INHIBITORY AMINO-ACID RECEPTORS ON HORIZONTAL CELLS ISOLATED FROM THE WHITE PERCH RETINA, Journal of neurophysiology, 70(1), 1993, pp. 8-19
1. The distribution and the properties of receptors to the inhibitory
amino acid glycine (GLY) and the excitatory amino acid glutamate (GLU)
and its analogues kainate (KA), quisqualate (QUIS), lpha-amino-3-hydr
oxy-5-methyl-4-isoxazolepropionic acid (AMPA), and N-methyl-D-aspartat
e (NMDA), were studied with whole-cell and outside-out patch-clamp tec
hniques on all four types of horizontal cells isolated from the retina
of white perch. 2. Glycine at concentrations above 30 muM evoked whol
e-cell current responses from two types of horizontal cells (H2 and H4
). The other two types of horizontal cells (H1 and H3) were unresponsi
ve to GLY (30 muM-3 mM). 3. Responses elicited by GLY from H2 and H4 c
ells were similar, consisting of inward currents that desensitized wit
h a half-decay time of 0.5-2 s at glycine concentrations between 100 a
nd 500 AM. GLY-activated currents were inhibited by the glycine recept
or antagonist strychnine (STRYCH). Current responses evoked by GLY rev
ersed at the Cl- equilibrium potential. 4. Dose-response analysis of p
eak currents induced by GLY revealed a Hill coefficient of 2.0 +/- 0.1
(mean +/- SD, n = 3) and an median effective concentration (EC50) of
85 +/- 2 muM (n = 3). 5. Single glycine receptor channels recorded fro
m outside-out patches had a main-state conductance of 47 +/- 4 pS (n =
3). 6. Every type of horizontal cell from the white perch responded t
o GLU, KA, QUIS, and AMPA but none responded to exogenously applied NM
DA (200 muM) or NMDA (200 muM) + GLY (1 muM) in a Mg+2-free bathing so
lution. 7. The ratio of the amplitude of responses to GLU, KA, QUIS, a
nd AMPA remained nearly constant among all the horizontal cells tested
, suggesting there might be only a single population of non-NMDA recep
tors on these cells. 8. QUIS and KA both elicited responses from the h
orizontal cells. When applied together with KA, QUIS competitively ant
agonized the responses of horizontal cells to KA. 9. The results demon
strated the existence of an inhomogeneous distribution of strychnine-s
ensitive glycine receptors and a homogeneous distribution of non-NMDA
type glutamate receptors among the four types of white perch horizonta
l cells.