Sculpting the visual map: the distribution and function of serotonin-1A and serotonin-1B receptors in the optic tectum of the frog.
Agonists of serotonin (5-HT)-1 receptors modulate the synaptic strength of the connection between retinal ganglion cells and neurons of the frog optic tectum in brain slices (Brain Res. 1998;781:167-181). We have now used autoradiographic receptor binding techniques to determine the location of 5-HT1A and 5-HT1B binding sites in the laminated optic tectum. 5-HT1A binding sites, as labeled with [3H]8-hydroxy-dipropylaminotetralin (8-OH-DPAT), were highest in the superficial, retinorecipient layers of the tectum, intermediate in layers 6 and 7 and low in the remaining layers. Binding densities in all of these layers were unaffected by optic nerve lesion. 5-HT1B binding sites were visualized using [125I]iodocyanopindolol (ICYP). Binding densities were highest in the plexiform layers 5 and 7 and intermediate in layers 6 and 8. Binding sites were present at low levels in layer 9; however, optic nerve lesion resulted in a strong upregulation of these sites in this layer. Pharmacological manipulation of receptor activation resulted in changes in the activity-dependent visual map that is created at the tectum by retinal ganglion cell terminals. Chronic treatment of the tectum with SB-224289, a selective antagonist of 5-HT1B receptors, disrupted the topographic map. In contrast, exposure to WAY-100635, a selective antagonist of 5-HT1A receptors, refined it. We conclude that both 5-HT1A and 5-HT1B receptors are present in the adult frog tectum and that changes in their activation levels can produce changes in retinotectal transmission levels that drive visual plasticity in opposite directions.
Butt
Christopher M
CM
School of Biological Sciences, 101 T.H. Morgan Building, University of Kentucky, Lexington, KY 40506-0225, USA.
Zhao
Bing
B
Duncan
Marilyn J
MJ
Debski
Elizabeth A
EA
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000319:Adrenergic beta-Antagonists; D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D001931:Brain Mapping; D006651:Histocytochemistry; D007091:Image Processing, Computer-Assisted; D020120:Iodocyanopindolol; D009900:Optic Nerve / Q000502:physiology; D011894:Rana pipiens; D044302:Receptor, Serotonin, 5-HT1B; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism*; D044263:Receptors, Serotonin, 5-HT1; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists; D013477:Superior Colliculi / Q000033:anatomy & histology* / Q000187:drug effects / Q000378:metabolism*
D000319:Adrenergic beta-Antagonists; D044302:Receptor, Serotonin, 5-HT1B; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D020120:Iodocyanopindolol