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UPTAKE RECEPTORS FOR EXCITATORY AMINO ACIDS IN NEURONAL AND GLIAL PRIMARY CULTURES FROM THE RETINA. Ana Maria L~pez-Colom~ and Frida Somohano. Instituto de Fisiologla Celular, UNAM, Apartado 70-600, 04510 M@xico, D.F. M~xico. Excitatory amino acids (EAA) have been shown to have a trophic role during ontogeny at concentrations around one order of magnitude higher than those required for their function as classical neurotransmitters. Since glutamate extracellular concentration could be regulated through changes in the uptake system, we have characterized the uptake of 3H-D-Asp during in vitro (IV) differentiation in both neuron-enriched and glia-enriched retinal cultures. In both systems 3H-D-Asp uptake was found to be Na +- and temperature-dependent, and inhibited by L-GIu, L-Asp and DL-Asp-~-hidroxamate with ICso's under 100~M, at all ages studied. Kinetic properties however varied considerably according to the type of culture: in neuron-enriched cultures, we found a single saturable system with a Km ~:I0 ~tM at all ages, showing a i0 fold increase in Vmax from the first to the 8th day IV. Uptake system in glia-enriched cultures shows a Km ffi 80 ~M at i DIV, which increases to 140 ~M between DIV 8 and 12. The Vmax also changes in glial cells between DIV i and 8, increasing from 30 to 200 nmoles/mg prot leveling at 120 nmoles/mg prot at 12 DIV. Our data suggest that there are 2 different uptake systems for EAA in neurons and glia and that the latest might be responsible for regulating the extracellular glutamate concentration during development. Supported in part by grant P228CCOX891617 from CONACyT.

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A M P A Recep tor Agonists . Design, Synthes i s and M o l e c u l a r P h a r m a c o l o g y . Trine M. Lund, Ingc T. Christensen, Ulf Madsen, Bjarke Ebert, Lotte Brehm and Povl Krogsgaard-Larsen, Royal Danish School of Pharmacy, DK-2100 Copenhagen.

Ibotenic acid has been extensively used as a lead structure for the design of a number of AMPA receptor agonists having the isoxazole moiety in common. Whereas the glutamic acid analogues AMPA and ATPA arc selective A M P A receptor agonists, the structurally related homologues 4-Mc-HIBO, 4-Bu-HIBO and, in )articular, 4 -AHCP show more complex biological profiles. Thus, although 4-AHCP specifically inhibits ~H-AMPA binding, it is capable of stimulating the binding of 3H-MK-801.

HOOC OH HOOC HOOC R OH H ~ N %

~'0" "*"""~ 0" N - ~ 0 ~'N H~N H~N

Ibotenic acid AMPA ATPA 4-Alkyl-HIBO 4-AHCP

80 PUN+CTIONAL ANATOMY O F S E I Z U R E S EVOKED F R O M AREA. TEMPEST.AS k Ma ggia, R.F. Ack ~,mann* and K. Gale, I~par tment of Phanna~ logy , Georgetown University Medic~ Center, Wna~iz~cm,

~ * D ~ p ~ n t ~ ~ , , ~ o ~ , U C L ~ S ~ o f M ~ , L ~ ~.le.,,, .c~ u.s .A_ . . We peffor2med autoradmglaphic analyses of brain sections from rats recetvmg ~C-2<Ieoxyglu~ee (2DG) dur ing bilateral motor ew.izures evoked fix~m axx epfleptogenie site in the d~ep Zp~epiriform vortex, "area tempestas = (AT). Seimm~ evoked from AT have been previousty d ~ w n to be dependent upon activation of N'MDA.sen~i~ve n~oeptcrs in this site. Ka in~ acid (K/0, when infused Lnt~ AT unilaterelly in doses at or above 100 pmoles, evokes recurve~ bilateral | ! r - ~ c motor s e ~ n ' e s that cam be 1 locke, d ~ compettLiv~ ]qMDA receptor entagDI~4s applied to the ~.Am~ locus. This suggests tha t KA ~ a c f i n 8 in AT to evoke l l u t ama te release onto NMDA recep to~ KA (250 pmoD was infused ,ni latoral]y iEd~o AT a l ~ atq~r t.he ~ coavliL~ve 8eislil'~, ~DG was ~ ac. Rats were saerifu~ed I hr later; b i la t~a] seizures fforelimb donus + rearing) c c e t m ~ at ~ 5 rain iT~rvals during this time. Markedly enhA~--~t 2DG accumulation occurred selectively in limbi¢ ~ ipeilateral to the ~tir, ulated AT; entor]hinal cortex, ven/raI h i ~ m p u s , amy grl ~l A_. r,.. ~ l i l i l ld ~ ~tl'e]lnlJil, i~i i r l~tnml ~oril~[, th8 • ,entrvmedial c a u d a ~ ~q, tum algJ olfa~ory bulb. Pronounced bilateral activation oocurvvd in med/mlorlm] and vlmt~olatora/ tha lamus and substanba ~ modest ~ : r tmses w ~ seen bi]atorally in dorsed hippocamlms. Imeusion of KA ~ to AT r, eit.h~r induced convulsions nor activated the structures described above, stlggesti]lg that the patten1 seen with AT ~!f11~o1~ was associated with epileptogenic mocha~k-m~ Except for highly differentiated activation of thalamic D, lcle|, s t r u c t m ~ at'tivated by AT-triggered seizures were the same as during amygdala-kindled se~ure~ This supp+,-~ the idea that AT is part ef an excitatory ~rni,,~acid mediated seizure generating circuit wit3fia the limbie system and also mnf l rms the bilatm'al involvement of substanti~ nigra as a conmstent feature of seigure generalizatior~