GABA-B-related activity in processing of transcallosal response in cat motor cortex.
GABA-ergic characteristics of transcallosal (TC) responses were studied with specific antagonists of both GABA-A and GABA-B receptor subtypes. We used a paired-pulse paradigm to get insight into the role of GABA in interhemispheric interactions between motor cortices. 3-Amino-2-(4-chlorophenyl)-propylphosphonic acid (phaclofen) and 3-aminopropyl-diethoxymethyl-phosphinic acid (CGP 35348) were used as GABA-B antagonists and bicuculline methiodide (BMI) was used to block the GABA-A receptor. Although both GABA-A and GABA-B antagonists increased spike discharge upon transcallosal stimulation, in both pyramidal tract and non-pyramidal tract neurons, they had different effects on the responses to the first and second stimuli of paired-pulse stimulation (200 msec interval). Although the inhibition seen with the second stimulus was greatly attenuated by antagonists of the GABA-B receptor, it was maintained in the presence of the GABA-A antagonist. These finding support a presynaptic regulation of callosal transmission by GABA-B receptors in the callosal synapse of the cat motor cortex.
Chowdhury
Syed A
SA
Institute of Equilibrium Research, School of Medicine, Gifu University, Gifu, Japan. schowdhu@is.dal.ca
Matsunami
Ken Ichi
KI
D000818:Animals; D001418:Baclofen / Q000031:analogs & derivatives* / Q000494:pharmacology; D001640:Bicuculline / Q000031:analogs & derivatives* / Q000494:pharmacology; D002415:Cats; D003337:Corpus Callosum / Q000187:drug effects* / Q000378:metabolism*; D005260:Female; D018755:GABA Agonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D008297:Male; D009044:Motor Cortex / Q000187:drug effects* / Q000378:metabolism*; D009943:Organophosphorus Compounds / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism*; D018080:Receptors, GABA-B / Q000187:drug effects / Q000378:metabolism*; D017661:Receptors, Presynaptic / Q000187:drug effects / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects
D018755:GABA Agonists; D018756:GABA Antagonists; D009943:Organophosphorus Compounds; D011963:Receptors, GABA-A; D018080:Receptors, GABA-B; D017661:Receptors, Presynaptic; C052329:phaclofen; C017069:bicuculline methiodide; C066430:CGP 35348; D001418:Baclofen; D001640:Bicuculline