Pharmacology of the GABAB receptor in amphibian retina.
Amacrine and ganglion cells in the amphibian retina contain GABAB, as well as GABAA, receptors. Baclofen, a GABAB agonist, hyperpolarizes the dark membrane potential of these third order neurons and makes their light responses more transient. GABAB receptors in the retina have a similar agonist profile to GABAB receptors described at other sites in the brain. Namely, preferential activation by the R-enantiomer of baclofen, and agonist sensitivity in the order 3-aminopropylphosphinic acid > baclofen >> 3-aminopropylphosphonic acid. The GABAB receptor was not activated by 4-aminobutylphosphonic acid. Several antagonists, such as phaclofen, saclofen, and 2-hydroxysaclofen, were ineffective in the amphibian retina. However, CGP35348 blocked the action of applied baclofen and produced effects on the light response that were opposite to those of baclofen. Applied agonists and antagonists support the hypothesis that GABAB receptors serve to regulate the balance of sustained and transient signals to the inner retina.
Tian
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Department of Biophysical Sciences, School of Medicine, State University of New York, Buffalo 14214.
Slaughter
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MM
D000557:Ambystoma; D000818:Animals; D001418:Baclofen / Q000031:analogs & derivatives / Q000494:pharmacology*; D002082:Butylamines / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009337:Necturus; D009943:Organophosphorus Compounds / Q000494:pharmacology; D011437:Propylamines / Q000494:pharmacology; D018080:Receptors, GABA-B / Q000502:physiology*; D012160:Retina / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000502:physiology*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D002082:Butylamines; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D009943:Organophosphorus Compounds; D011437:Propylamines; D018080:Receptors, GABA-B; C061388:3-aminopropylphosphinic acid; C052329:phaclofen; C079360:4-aminobutylphosphonic acid; C066430:CGP 35348; D001418:Baclofen; C080629:saclofen; C011649:3-aminopropylphosphonic acid; C057491:2-hydroxysaclofen