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GABAB-Receptor-mediated currents in interneurons of the dentate-hilus border.

Publication ,  Journal Article
Mott, DD; Li, Q; Okazaki, MM; Turner, DA; Lewis, DV
Published in: J Neurophysiol
September 1999

GABA(B)-receptor-mediated inhibition was investigated in anatomically identified inhibitory interneurons located at the border between the dentate gyrus granule cell layer and hilus. Biocytin staining was used to visualize the morphology of recorded cells. A molecular layer stimulus evoked a pharmacologically isolated slow inhibitory postsynaptic current (IPSC), recorded with whole cell patch-clamp techniques, in 55 of 63 interneurons. Application of the GABA(B) receptor antagonists, CGP 35348 (400 microM) or CGP 55845 (1 microM) to a subset of 25 interneurons suppressed the slow IPSC by an amount ranging from 10 to 100%. In 56% of these cells, the slow IPSC was entirely GABA(B)-receptor-mediated. However, in the remaining interneurons, a component of the slow IPSC was resistant to GABA(B) antagonists. Subtraction of this antagonist resistant current from the slow IPSC isolated the GABA(B) component (IPSC(B)). This IPSC(B) had a similar onset and peak latency to that recorded from granule cells but a significantly shorter duration. The GABA(B) agonist, baclofen (10 microM), produced a CGP 55845-sensitive outward current in 19 of 27 interneurons. In the eight cells that lacked a baclofen current, strong or repetitive ML stimulation also failed to evoke an IPSC(B), indicating that these cells lacked functional GABA(B) receptor-activated potassium currents. In cells that expressed a baclofen current, the amplitude of this current was approximately 50% smaller in interneurons with axons that projected into the granule cell dendritic layer (22.2 +/- 5.3 pA; mean +/- SE) than in interneurons with axons that projected into or near the granule cell body layer (46.1 +/- 10.0 pA). Similarly, the IPSC(B) amplitude was smaller in interneurons projecting to dendritic (9.4 +/- 2.7 pA) than perisomatic regions (34.3 +/- 5.1 pA). These findings suggest that GABA(B) inhibition more strongly regulates interneurons with axons that project into perisomatic than dendritic regions. To determine the functional role of GABA(B) inhibition, we examined the effect of IPSP(B) on action potential firing and synaptic excitation of these interneurons. IPSP(B) and IPSP(A) both suppressed depolarization-induced neuronal firing. However, unlike IPSP(A), suppression of firing by IPSP(B) could be easily overcome with strong depolarization. IPSP(B) markedly suppressed N-methyl-D-aspartate but not AMPA EPSPs, suggesting that GABA(B) inhibition may play a role in regulating slow synaptic excitation of these interneurons. Heterogeneous expression of GABA(B) currents in hilar border interneurons therefore may provide a mechanism for the differential regulation of excitation of these cells and thereby exert an important role in shaping neuronal activity in the dentate gyrus.

Duke Scholars

Published In

J Neurophysiol

DOI

ISSN

0022-3077

Publication Date

September 1999

Volume

82

Issue

3

Start / End Page

1438 / 1450

Location

United States

Related Subject Headings

  • Synapses
  • Receptors, GABA-B
  • Rats, Sprague-Dawley
  • Rats
  • Neurology & Neurosurgery
  • Neural Inhibition
  • N-Methylaspartate
  • Male
  • Kinetics
  • Interneurons
 

Citation

APA
Chicago
ICMJE
MLA
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Mott, D. D., Li, Q., Okazaki, M. M., Turner, D. A., & Lewis, D. V. (1999). GABAB-Receptor-mediated currents in interneurons of the dentate-hilus border. J Neurophysiol, 82(3), 1438–1450. https://doi.org/10.1152/jn.1999.82.3.1438
Mott, D. D., Q. Li, M. M. Okazaki, D. A. Turner, and D. V. Lewis. “GABAB-Receptor-mediated currents in interneurons of the dentate-hilus border.J Neurophysiol 82, no. 3 (September 1999): 1438–50. https://doi.org/10.1152/jn.1999.82.3.1438.
Mott DD, Li Q, Okazaki MM, Turner DA, Lewis DV. GABAB-Receptor-mediated currents in interneurons of the dentate-hilus border. J Neurophysiol. 1999 Sep;82(3):1438–50.
Mott, D. D., et al. “GABAB-Receptor-mediated currents in interneurons of the dentate-hilus border.J Neurophysiol, vol. 82, no. 3, Sept. 1999, pp. 1438–50. Pubmed, doi:10.1152/jn.1999.82.3.1438.
Mott DD, Li Q, Okazaki MM, Turner DA, Lewis DV. GABAB-Receptor-mediated currents in interneurons of the dentate-hilus border. J Neurophysiol. 1999 Sep;82(3):1438–1450.

Published In

J Neurophysiol

DOI

ISSN

0022-3077

Publication Date

September 1999

Volume

82

Issue

3

Start / End Page

1438 / 1450

Location

United States

Related Subject Headings

  • Synapses
  • Receptors, GABA-B
  • Rats, Sprague-Dawley
  • Rats
  • Neurology & Neurosurgery
  • Neural Inhibition
  • N-Methylaspartate
  • Male
  • Kinetics
  • Interneurons