Activation of postsynaptic GABAB receptors modulates the bursting pattern and synaptic activity of olfactory bulb juxtaglomerular neurons

J Neurophysiol. 2008 Jan;99(1):308-19. doi: 10.1152/jn.01086.2007. Epub 2007 Nov 21.


Olfactory bulb glomeruli are formed by a network of three major types of neurons collectively called juxtaglomerular (JG) cells, which include external tufted (ET), periglomerular (PG), and short axon (SA) cells. There is solid evidence that gamma-aminobutyric acid (GABA) released from PG neurons presynaptically inhibits glutamate release from olfactory nerve terminals via activation of GABA(B) receptors (GABA(B)-Rs). However, it is still unclear whether ET cells have GABA(B)-Rs. We have investigated whether ET cells have functional postsynaptic GABA(B)-Rs using extracellular and whole cell recordings in olfactory bulb slices. In the presence of fast synaptic blockers (CNQX, APV, and gabazine), the GABA(B)-R agonist baclofen either completely inhibited the bursting or reduced the bursting frequency and increased the burst duration and the number of spikes/burst in ET cells. In the presence of fast synaptic blockers and tetrodotoxin, baclofen induced an outward current in ET cells, suggesting a direct postsynaptic effect. Baclofen reduced the frequency and amplitude of spontaneous EPSCs in PG and SA cells. In the presence of sodium and potassium channel blockers, baclofen reduced the frequency of miniature EPSCs, which were inhibited by the calcium channel blocker cadmium. All baclofen effects were reversed by application of the GABA(B)-R antagonist CGP55845. We suggest that activation of GABA(B)-Rs directly inhibits ET cell bursting and decreases excitatory dendrodendritic transmission from ET to PG and SA cells. Thus the postsynaptic GABA(B)-Rs on ET cells may play an important role in shaping the activation pattern of the glomeruli during olfactory coding.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology*
  • Animals
  • Baclofen / pharmacology
  • Excitatory Postsynaptic Potentials / drug effects
  • Excitatory Postsynaptic Potentials / physiology
  • Female
  • GABA Agonists / pharmacology
  • Interneurons / metabolism
  • Interneurons / ultrastructure
  • Male
  • Neural Inhibition / drug effects
  • Neural Inhibition / physiology
  • Neurons / metabolism*
  • Neurons / ultrastructure
  • Neuropil / metabolism
  • Neuropil / ultrastructure
  • Olfactory Bulb / metabolism*
  • Olfactory Bulb / ultrastructure
  • Olfactory Nerve / metabolism
  • Olfactory Nerve / ultrastructure
  • Patch-Clamp Techniques
  • Presynaptic Terminals / metabolism
  • Presynaptic Terminals / ultrastructure
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, GABA-B / drug effects
  • Receptors, GABA-B / metabolism*
  • Smell / drug effects
  • Smell / physiology
  • Synapses / metabolism*
  • Synapses / ultrastructure
  • Synaptic Membranes / metabolism
  • Synaptic Membranes / ultrastructure
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology
  • gamma-Aminobutyric Acid / metabolism


  • GABA Agonists
  • Receptors, GABA-B
  • gamma-Aminobutyric Acid
  • Baclofen