Transient calcium current of retinal bipolar cells of the mouse.

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. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Physiology Wiley

Transient calcium current of retinal bipolar cells of the mouse.

The Journal of Physiology, Volume 410 (1) – Mar 1, 1989

Loading next page...
 
/lp/wiley/transient-calcium-current-of-retinal-bipolar-cells-of-the-mouse-5jL03d7Xar
Publisher
Wiley
Copyright
© 2014 The Physiological Society
ISSN
0022-3751
eISSN
1469-7793
D.O.I.
10.1113/jphysiol.1989.sp017551
Publisher site
See Article on Publisher Site

Abstract

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.

Journal

The Journal of PhysiologyWiley

Published: Mar 1, 1989

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create folders to
organize your research

Export folders, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off