Journal of Neurophysiology, Vol 74, Issue 4 1473-1484, Copyright © 1995 by APS

ARTICLES

GABA receptors precede glutamate receptors in hypothalamic development; differential regulation by astrocytes

G. Chen, P. Q. Trombley and A. N. van den Pol
Section of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut 06520, USA.

1. The developmental changes in gamma-aminobutyrate (GABA)-, glutamate-, and glycine-mediated currents in cultured embryonic neurons (n = 134) from rat hypothalamus were studied with the use of whole cell voltage-clamp recording. 2. GABA-evoked currents were detected in neurons cultured from 15-day embryos (E15) a few hours after plating. Every neuron studied from the time of plating at E15 to 2 wk later responded to GABA (30 microM). The peak and steady-state currents evoked by GABA increased by four- to fivefold within 2 wk in culture. The time constants of the desensitization of GABA currents did not change during this period. The properties of the responses to GABA were not altered by different culture densities or substrates. 3. Glycine activated receptors that were pharmacologically distinct from GABA receptors on hypothalamic neurons. The glycine responses increased by > 50-fold within 2 wk in culture. The percentage of cells responding to glycine (500 microM) was 20% at 0 days in vitro (DIV), and increased to 100% at 6 DIV. Astrocytes increased both the amplitude of glycine-mediated currents and the percentage of cells responding to glycine. 4. Glutamate-mediated currents developed later than GABA-mediated currents. The percentage of cells responding to glutamate (500 microM) increased within the 1st wk, from 20% on the day of plating to 100% after 6 DIV. Both the peak currents and the steady-state currents mediated by glutamate increased by 20-fold during the 2 wk in culture. Both the amplitude of the responses to glutamate and the percentage of cells responding to glutamate were increased by growing neurons either on an astrocyte substrate or in high-density cultures. 5. The currents and conductance changes elicited by GABA were greater than those generated by glutamate or glycine throughout the period examined. This difference was particularly evident in younger cells. After 3 days in vitro, GABA (30 microM) elicited a mean current of 1,648 pA, whereas glutamate (500 microM) only elicited a 266-pA current, and glycine (500 microM) elicited a 278-pA current from neurons growing on an astrocyte layer. 6. The expression of amino acid receptors was heterogeneous among hypothalamic neurons in younger cultures. Whereas all neurons expressed GABA receptors, some developing neurons did not express detectable glutamate receptors or glycine receptors. 7. Each of the three amino acid-evoked currents increased from E15 (1 DIV) to E20 (1 DIV), indicating an intrinsic development in the expression of the amino acid receptors in vivo. The GABA, glutamate, and glycine currents at E15, 10 DIV were similar to the currents at E20, 5 DIV (both 25 days after conception), suggesting parallel developmental patterns for amino acid receptor expression in vitro and in vivo. 8. Together, these data suggest that GABA may play a major role in early development because hypothalamic neurons are more sensitive to GABA than to either glutamate or glycine. However, glutamate and glycine receptors appear more sensitive to regulation by the local environment than GABA receptors because culture density and the astrocyte substrate have greater inductive effects on glutamate and glycine receptors than on GABA receptors.

This article has been cited by other articles:

				J. C. Wilhelm and P. Wenner GABAA transmission is a critical step in the process of triggering homeostatic increases in quantal amplitude PNAS, August 12, 2008; 105(32): 11412 - 11417. [Abstract] [Full Text] [PDF]

				D. D. Wang and A. R. Kriegstein GABA Regulates Excitatory Synapse Formation in the Neocortex via NMDA Receptor Activation J. Neurosci., May 21, 2008; 28(21): 5547 - 5558. [Abstract] [Full Text] [PDF]

				Y. Ben-Ari, J.-L. Gaiarsa, R. Tyzio, and R. Khazipov GABA: A Pioneer Transmitter That Excites Immature Neurons and Generates Primitive Oscillations Physiol Rev, October 1, 2007; 87(4): 1215 - 1284. [Abstract] [Full Text] [PDF]

				H. Gozlan and Y. Ben-Ari Interneurons are the Source and the Targets of the First Synapses Formed in the Rat Developing Hippocampal Circuit Cereb Cortex, June 1, 2003; 13(6): 684 - 692. [Abstract] [Full Text] [PDF]

				A. B. Belousov, N. D. Hunt, R. P. Raju, and J. V. Denisova Calcium-Dependent Regulation of Cholinergic Cell Phenotype in the Hypothalamus In Vitro J Neurophysiol, September 1, 2002; 88(3): 1352 - 1362. [Abstract] [Full Text] [PDF]

				K. Obrietan, X.-B. Gao, and A. N. van den Pol Excitatory Actions of GABA Increase BDNF Expression via a MAPK-CREB-Dependent Mechanism---A Positive Feedback Circuit in Developing Neurons J Neurophysiol, August 1, 2002; 88(2): 1005 - 1015. [Abstract] [Full Text] [PDF]

				A. B. Belousov, B. F. O'Hara, and J. V. Denisova Acetylcholine Becomes the Major Excitatory Neurotransmitter in the Hypothalamus In Vitro in the Absence of Glutamate Excitation J. Neurosci., March 15, 2001; 21(6): 2015 - 2027. [Abstract] [Full Text] [PDF]

				X.-B. Gao and A. N. Van Den Pol GABA, Not Glutamate, a Primary Transmitter Driving Action Potentials in Developing Hypothalamic Neurons J Neurophysiol, January 1, 2001; 85(1): 425 - 434. [Abstract] [Full Text] [PDF]

				Q.-Y. Liu, A. E. Schaffner, Y. H. Chang, D. Maric, and J. L. Barker Persistent Activation of GABAA Receptor/Cl- Channels by Astrocyte-Derived GABA in Cultured Embryonic Rat Hippocampal Neurons J Neurophysiol, September 1, 2000; 84(3): 1392 - 1403. [Abstract] [Full Text] [PDF]

				X.-B. Gao and A. N van den Pol GABA release from mouse axonal growth cones J. Physiol., March 15, 2000; 523(3): 629 - 637. [Abstract] [Full Text] [PDF]

				R. Tyzio, A. Represa, I. Jorquera, Y. Ben-Ari, H. Gozlan, and L. Aniksztejn The Establishment of GABAergic and Glutamatergic Synapses on CA1 Pyramidal Neurons is Sequential and Correlates with the Development of the Apical Dendrite J. Neurosci., December 1, 1999; 19(23): 10372 - 10382. [Abstract] [Full Text] [PDF]

				C. Y. Chiang, C. L. Kwan, J. W. Hu, and B. J. Sessle Effects of GABA Receptor Antagonist on Trigeminal Caudalis Nociceptive Neurons in Normal and Neonatally Capsaicin-Treated Rats J Neurophysiol, November 1, 1999; 82(5): 2154 - 2162. [Abstract] [Full Text] [PDF]

				X.-B. Gao and A N van den Pol Neurotrophin-3 potentiates excitatory GABAergic synaptic transmission in cultured developing hypothalamic neurones of the rat J. Physiol., July 1, 1999; 518(1): 81 - 95. [Abstract] [Full Text] [PDF]

				A. N. van den Pol, X.-B. Gao, P. R. Patrylo, P. K. Ghosh, and K. Obrietan Glutamate Inhibits GABA Excitatory Activity in Developing Neurons J. Neurosci., December 15, 1998; 18(24): 10749 - 10761. [Abstract] [Full Text] [PDF]

				G. Chen and A. N. van den Pol Coexpression of Multiple Metabotropic Glutamate Receptors in Axon Terminals of Single Suprachiasmatic Nucleus Neurons J Neurophysiol, October 1, 1998; 80(4): 1932 - 1938. [Abstract] [Full Text] [PDF]

				K. Obrietan and A. N. van den Pol GABAB Receptor-Mediated Inhibition of GABAA Receptor Calcium Elevations in Developing Hypothalamic Neurons J Neurophysiol, March 1, 1998; 79(3): 1360 - 1370. [Abstract] [Full Text] [PDF]

				X.-B. Gao, G. Chen, and A. N. van den Pol GABA-Dependent Firing of Glutamate-Evoked Action Potentials at AMPA/Kainate Receptors in Developing Hypothalamic Neurons J Neurophysiol, February 1, 1998; 79(2): 716 - 726. [Abstract] [Full Text] [PDF]

				G. Chen and A. N. van den Pol Adenosine Modulation of Calcium Currents and Presynaptic Inhibition of GABA Release in Suprachiasmatic and Arcuate Nucleus Neurons J Neurophysiol, June 1, 1997; 77(6): 3035 - 3047. [Abstract] [Full Text] [PDF]

				G. Chen and A. N. van den Pol Multiple NPY Receptors Coexist in Pre- and Postsynaptic Sites: Inhibition of GABA Release in Isolated Self-Innervating SCN Neurons J. Neurosci., December 1, 1996; 16(23): 7711 - 7724. [Abstract] [Full Text] [PDF]

				K. Obrietan and A. N. van den Pol Neuropeptide Y Depresses GABA-Mediated Calcium Transients in Developing Suprachiasmatic Nucleus Neurons: A Novel Form of Calcium Long-Term Depression J. Neurosci., May 15, 1996; 16(10): 3521 - 3533. [Abstract] [Full Text] [PDF]