Hippocampal mGluR1 and consolidation of contextual fear conditioning.
The effects of post-training intra-hippocampal injections of group I mGluR agonists and antagonists, were examined in the contextual fear test, in rats. It was found that (S)-3,5-dihydroxyphenylglycine (DHPG) (a mGluR1-5 agonist) decreased, and (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA) (a mGluR1 antagonist) increased fear conditioning (a freezing reaction), examined 24h after conditioning session. (RS)-2-Chloro-5-hydroxyphenylglycine (CHPG) (a mGluR5 agonist), and 2-methyl-6-(phenylethynyl)pyridine hydrochloride (MPEP) (a mGluR5 antagonist) did not cause any effect. In the immunocytochemical study, the post-conditioning administration of AIDA decreased the c-Fos induction in the dentate gyrus and CA1 layer of the hippocampus proper, 2h after exposure of animals to the aversive context, and 24h after conditioning session. It is suggested that overactivation of glutamatergic transmission in the critical for memory trace formation structure and period of time, may result in an attenuation of memory consolidation. On the other hand, reduction of an exaggerated glutamatergic tone can facilitate learning and memory processes. The immunocytochemical study and factor analysis of experimental data revealed that hippocampal mGlu1 receptors significantly influence the memory consolidation in a way dependant on the level of glutamatergic activity. Furthermore, they indicate that changes of glutamatergic activity within brain limbic structures can affect the threshold for the induction of the long-term neuronal plasticity, involved in some forms of learning and memory.
Maciejak
Piotr
P
Department of Neurochemistry, Institute of Psychiatry and Neurology, 9 Sobieskiego Street, 02-957, Warsaw, Poland.
Taracha
Ewa
E
Lehner
Małgorzata
M
Szyndler
Janusz
J
Bidziński
Andrzej
A
Skórzewska
Anna
A
Wisłowska
Aleksandra
A
Zienowicz
Małgorzata
M
Płaźnik
Adam
A
D000818:Animals; D001522:Behavior, Animal; D002467:Cell Nucleus / Q000378:metabolism; D003216:Conditioning, Operant; D003213:Conditioning, Psychological / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005163:Factor Analysis, Statistical; D005239:Fear / Q000502:physiology*; D006624:Hippocampus / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D007103:Immobilization; D007150:Immunohistochemistry; D007189:Indans / Q000494:pharmacology; D008297:Male; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives* / Q000494:pharmacology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D013997:Time Factors
C095756:1-aminoindan-1,5-dicarboxylic acid; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D007189:Indans; D016760:Proto-Oncogene Proteins c-fos; D018094:Receptors, Metabotropic Glutamate; C104077:metabotropic glutamate receptor type 1; D008734:Methoxyhydroxyphenylglycol; C010117:3,4-dihydroxyphenylglycol