Transient calcium current of retinal bipolar cells of the mouse.

1. Isolated bipolar cells were obtained by enzymic (papain) dissociation of the adult mouse retina. The membrane voltage was clamped and the membrane currents were measured by the whole‐cell version of the patch‐clamp technique. Isolated bipolar cells and horizontal cells of the goldfish retina were also studied for comparison. 2. Hyperpolarization from the holding voltage, Vh, of ‐46 mV evoked a slowly activating, Cs+‐sensitive, inward current (probably an h‐current), and depolarization evoked a TEA‐ and Cs+‐sensitive outward current (probably a combination of K+ currents). 3. Depolarization from a more negative Vh (e.g. ‐96 mV) evoked a transient inward current that had maximal amplitude between ‐40 and ‐20 mV. This current was identified as a Ca2+ current (ICa): its amplitude was increased with elevated [Ca2+]o and was decreased with reduced [Ca2+]o, and it was blocked by 4 mM‐Co2+, but not by 5 microM‐TTX. 4. Both the perikaryon and the axon terminal generated ICa with similar properties. 5. The plot of Ca2+ conductance (gCa) against membrane voltage (activation curve) was sigmoidal: in 10 mM [Ca2+]o, gCa increased for membrane voltages more positive than ‐65 mV, was half‐maximal at about ‐25 mV, and reached saturation at about +30 mV. The plot of inactivation of gCa against membrane voltage was also sigmoidal: with 1 s conditioning depolarization in 10 mM [Ca2+]o, gCa decreased for membrane voltages more positive than ‐80 mV, was half‐maximal at about ‐50 mV, and was fully suppressed for voltages greater than ‐30 mV. 6. ICa in the mouse bipolar cells was insensitive to 50 microM‐Cd2+, 10 microM‐nifedipine and 10 microM‐Bay K 8644. In contrast, the calcium currents of bipolar and horizontal cells of the goldfish retina were markedly suppressed by 50 microM‐Cd2+ and 10 microM‐nifedipine, and were augmented several fold by 10 microM‐Bay K 8644. The calcium currents of goldfish bipolar and horizontal cells were sustained, and were activated in a more positive range of potentials than the ICa of mouse bipolar cells. 7. The voltage range at which the ICa of mouse bipolar cells is activated includes the presumed range of membrane potentials spanned during light‐evoked responses; thus, this current may participate in synaptic transmission. The transient character of ICa may also help to shape transient responses of ganglion cells.

[1]  N. Hagiwara,et al.  Contribution of two types of calcium currents to the pacemaker potentials of rabbit sino‐atrial node cells. , 1988, The Journal of physiology.

[2]  R. Tsien,et al.  Calcium channels: mechanisms of selectivity, permeation, and block. , 1987, Annual review of biophysics and biophysical chemistry.

[3]  A Kaneko,et al.  Effects of gamma‐aminobutyric acid on isolated cone photoreceptors of the turtle retina. , 1986, The Journal of physiology.

[4]  L. Pinto,et al.  Response properties of horizontal cells in the isolated retina of wild- type and pearl mutant mice , 1986, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[5]  R. Tsien,et al.  A novel type of cardiac calcium channel in ventricular cells , 1985, Nature.

[6]  R. Tsien,et al.  Three types of neuronal calcium channel with different calcium agonist sensitivity , 1985, Nature.

[7]  A. Kaneko,et al.  A voltage‐clamp analysis of membrane currents in solitary bipolar cells dissociated from Carassius auratus. , 1985, The Journal of physiology.

[8]  M. Tachibana,et al.  Permeability changes induced by L‐glutamate in solitary retinal horizontal cells isolated from Carassius auratus. , 1985, The Journal of physiology.

[9]  D. Baylor,et al.  The photocurrent, noise and spectral sensitivity of rods of the monkey Macaca fascicularis. , 1984, The Journal of physiology.

[10]  L. Pinto,et al.  Visually evoked eye movements in mouse mutants and inbred strains. A screening report. , 1984, Investigative ophthalmology & visual science.

[11]  A Kaneko,et al.  Responses of solitary retinal horizontal cells from Carassius auratus to L‐glutamate and related amino acids. , 1984, The Journal of physiology.

[12]  H. Kolb,et al.  Chapter 2 Neural architecture of the cat retina , 1984 .

[13]  M. Tachibana,et al.  Membrane properties of solitary horizontal cells isolated from goldfish retina. , 1981, The Journal of physiology.

[14]  A. Marty,et al.  Ca-dependent K channels with large unitary conductance in chromaffin cell membranes , 1981, Nature.

[15]  D. Potter,et al.  Studies on rat sympathetic neurons developing in cell culture. I. Growth characteristics and electrophysiological properties. , 1978, Developmental biology.

[16]  A Kaneko,et al.  Neuronal architecture of on and off pathways to ganglion cells in carp retina. , 1977, Science.

[17]  S. W. Kuffler.  Neurons in the retina; organization, inhibition and excitation problems. , 1952, Cold Spring Harbor symposia on quantitative biology.

[18]  W S Duke-Elder,et al.  THE STRUCTURE OF THE RETINA , 1926, The British journal of ophthalmology.