The action of GABAB antagonists in the trigeminal nucleus of the rat.
The iontophoretic administration of the GABAB antagonists (P-(3-aminopropyl)-P-diethoxymethyl-phosphinic acid (CGP 35348) and 2-hydroxy-saclofen blocked the action of iontophoretically applied L-baclofen on neurons in the trigeminal nucleus of rats, anesthetized with halothane. The substance CGP 35348 appeared to be more potent than 2-hydroxy-saclofen. The iontophoretic administration of GABA resembled L-baclofen in depressing excitatory transmission and facilitating segmental inhibition in the trigeminal nucleus. The depression of excitatory transmission was also blocked by CGP 35348 and the facilitation of segmental inhibition produced by GABA was partially blocked. These observations indicate that CGP 35348 is not only a baclofen antagonist but actually a GABAB receptor antagonist and the baclofen was acting at GABAB receptors in the trigeminal nucleus. The portion of the effect of GABA, not blocked by CGP 35348, was probably mediated by GABAA receptors, since it was previously found that segmental inhibition in the trigeminal nucleus could be modulated by GABAA agonists and antagonists as well.
Fromm
G H
GH
Department of Neurology, University of Pittsburgh, School of Medicine, PA 15261.
Sato
K
K
Nakata
M
M
D000818:Animals; D001418:Baclofen / Q000031:analogs & derivatives / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists; D009943:Organophosphorus Compounds / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014278:Trigeminal Nuclei / Q000187:drug effects*
D058787:GABA-A Receptor Antagonists; D009943:Organophosphorus Compounds; C066430:CGP 35348; D001418:Baclofen; C057491:2-hydroxysaclofen