title: The lemniscal-cuneate recurrent excitation is suppressed by strychnine and enhanced by GABAA antagonists in the anaesthetized cat.
abstract: In the somatosensory system, cuneolemniscal (CL) cells fire high frequency doublets of spikes facilitating the transmission of sensory information to diencephalic target cells. We studied how lemniscal feedback affects ascending transmission of cutaneous neurons of the middle cuneate nucleus. Electrical stimulation of the contralateral medial lemniscus and of the skin at sites evoking responses with minimal threshold induced recurrent activation of CL cells at a latency of 1-3.5 ms. The lemniscal feedback activation was suppressed by increasing the stimulating intensity at the same sites, suggesting recurrent-mediated lateral inhibition. The glycine antagonist strychnine blocked the recurrent excitatory responses while GABAA antagonists uncovered those obscured by stronger stimulation. CL cells sharing a common receptive field (RF) potentiate one another by recurrent activation and disinhibition, the disinhibition being produced by serial interactions between glycinergic and GABAergic interneurons. Conversely, CL cells with different RFs inhibit each other through recurrent GABA-mediated inhibition. The lemniscal feedback would thus enhance the surround antagonism of a centre response by increasing the spatial resolution and the transmission of weak signals.
authors.affiliation: Department of Physiology, Faculty of Medicine, Santiago de Compostela, Spain Department of Medicine, University La Coruña, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Aguilar
authors.forename: Cristina
authors.initials: C
authors.lastname: Soto
authors.forename: Casto
authors.initials: C
authors.lastname: Rivadulla
authors.forename: Antonio
authors.initials: A
authors.lastname: Canedo
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002415:Cats; D005260:Female; D018756:GABA Antagonists / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists; D018684:Glycine Agents / Q000494:pharmacology; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism*; D009778:Occipital Lobe / Q000187:drug effects / Q000502:physiology; D010852:Picrotoxin / Q000494:pharmacology; D012867:Skin / Q000294:innervation; D013331:Strychnine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D001640:Bicuculline; D018756:GABA Antagonists; D058787:GABA-A Receptor Antagonists; D018684:Glycine Agents; D010852:Picrotoxin; D013331:Strychnine; D005680:gamma-Aminobutyric Acid