Comparison of receptive field expansion produced by GABA(B) and GABA(A) receptor antagonists in raccoon primary somatosensory cortex.
Recordings were made from 62 neurons in the forepaw representation of primary somatosensory cortex in anesthetized raccoons. Microiontophoretic administration of a specific GABA(B) receptor antagonist, CGP 55845, produced receptive field expansion in 74% of 46 neurons, in which it was tested first. The mean receptive field area was approximately doubled, with increases ranging from 12 to 500%. The GABA(B) receptor agonist baclofen reduced the receptive field in most (11 of 16) neurons, but increased the size in 4 neurons. Comparison of the effects of GABA(B) and GABA(A) antagonists in the same cells showed that GABA(A) receptor blockade produced greater expansion than GABA(B) blockade (144% vs 114%, respectively). Simultaneous administration of the two antagonists produced additional expansion in 16 of 25 neurons. There was no evidence of separate skin regions being masked by the two GABA receptor subtypes, as the larger expansion usually included the skin that was unmasked by the less effective drug. These results indicate that both GABA(B) and GABA(A) receptors play a role in shaping the normal receptive fields in somatosensory cortex.
Chowdhury
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SA
Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7.
Rasmusson
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D000344:Afferent Pathways / Q000502:physiology*; D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D005260:Female; D005385:Fingers / Q000294:innervation / Q000502:physiology; D018755:GABA Agonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010721:Phosphinic Acids / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D011821:Raccoons; D018079:Receptors, GABA / Q000187:drug effects / Q000378:metabolism*; D011963:Receptors, GABA-A / Q000378:metabolism; D018080:Receptors, GABA-B / Q000378:metabolism; D012867:Skin / Q000294:innervation*; D013003:Somatosensory Cortex / Q000187:drug effects / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D014110:Touch / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018755:GABA Agonists; D018756:GABA Antagonists; D058787:GABA-A Receptor Antagonists; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D010721:Phosphinic Acids; D011412:Propanolamines; D018079:Receptors, GABA; D011963:Receptors, GABA-A; D018080:Receptors, GABA-B; C085075:CGP 55845A; D005680:gamma-Aminobutyric Acid; D001418:Baclofen