Loss of long-lasting potentiation mediated by group III mGluRs in amygdala neurons in kindling-induced epileptogenesis.
Long-lasting modifications of synaptic transmission can be induced in the amygdala by electrical stimulation as done in the long-term potentiation (LTP) model of learning and memory and the kindling model of epilepsy. The present study reports for the first time a long-lasting potentiation (LLP) of synaptic transmission that is induced pharmacologically by the activation of group III metabotropic glutamate receptors (mGluRs) in basolateral amygdala (BLA) neurons. In whole cell voltage-clamp mode, BLA neurons were recorded in brain slices from control rats and rats with amygdala-kindled seizures. The group III mGluR agonist -2-amino-4-phosphonobutyrate (-AP4, 10 microM) induced LLP of monosynaptic excitatory postsynaptic currents (EPSCs) evoked by electrical stimulation in the lateral amygdala (maximum 258 +/- 50% of predrug control; means +/- SE) in control (n = 7) but not in kindled neurons(n = 6). LLP was measured 15 min after the superfusion of -AP4, lasted for >45 min, and was not accompanied by postsynaptic membrane changes. -AP4 induced LLP was prevented by the group III mGluR antagonist (S)-2-methyl-2-amino-4-phosphonobutyrate (MAP4; 100 microM, n = 6) but not the group II mGluR antagonist (2S, 3S,4S)-2-methyl-2-carboxycyclopropylglycine (MCCG; 100 microM, n = 3). LLP was not observed after superfusion of the group II mGluR agonist (2S,3S,4S)-2-(carboxycyclopropyl)glycine (-CCG; 1.0 and 10 microM) in either control (n = 13) or kindled (n = 10) neurons. If the underlying mechanisms and the functional significance of pharmacologically induced LLP are similar to those of LTP, the loss of -AP4 induced LLP in kindled neurons may be a neurobiological correlate of learning and memory deficits in kindled animals and long-term alterations of brain functions in patients with epilepsies.
Neugebauer
V
V
Department of Pharmacology and Toxicology, The University of Texas Medical Branch, Galveston, Texas 77555-1031, USA.
Keele
N B
NB
Shinnick-Gallagher
P
P
D000600:Amino Acids, Dicarboxylic / Q000494:pharmacology; D000613:Aminobutyrates / Q000494:pharmacology; D000679:Amygdala / Q000166:cytology / Q000502:physiology*; D000818:Animals; D004827:Epilepsy / Q000473:pathology / Q000503:physiopathology*; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D007696:Kindling, Neurologic / Q000502:physiology*; D017774:Long-Term Potentiation; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology
C089836:2-amino-2-methyl-4-phosphonobutyrate; C089837:2-methyl-2-(2-carboxycyclopropyl)glycine; D000600:Amino Acids, Dicarboxylic; D000613:Aminobutyrates; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D018094:Receptors, Metabotropic Glutamate; C012729:2-amino-4-phosphonobutyric acid