(±)-α-Methyl-4-carboxyphenylglycine, a metabotropic glutamate receptor blocker, impairs retention of an inhibitory avoidance task in rats when infused into the basolateral nucleus of the amygdala

• Published in: Brain research 2000-01, Vol.852 (2), p.436-443
• Main Authors: Bianchin, Marino M., Spanis, Curt W., Roesler, Rafael, McGaugh, James L., Izquierdo, Ivan
• Format: Article
• Language: English
• Subjects: Amygdala - chemistry; Amygdala - drug effects; Amygdala - physiology; Animals; Avoidance Learning - drug effects; Avoidance Learning - physiology; Behavioral psychophysiology; Benzoates - pharmacology; Biological and medical sciences; Electroshock; Emotionally motivated learning; Emotions; Excitatory Amino Acid Antagonists - pharmacology; Fundamental and applied biological sciences. Psychology; Glutamatergic system; Glutamic Acid - physiology; Glycine - analogs & derivatives; Glycine - pharmacology; Male; Memory modulation; Microinjections; Neural Inhibition - drug effects; Neural Inhibition - physiology; Neurotransmission and behavior; Nociception; Nociceptors - drug effects; Nociceptors - physiology; Pain Threshold - drug effects; Pain Threshold - physiology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate - antagonists & inhibitors; Receptors, Metabotropic Glutamate - physiology; Retention (Psychology) - drug effects; Retention (Psychology) - physiology
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(99)02220-9

The amygdala is important for memory processes of emotionally motivated learning and the amygdala glutamatergic system may play a key role in this process. In this study we assessed the effect of the infusion of (±)-α-methyl-4-carboxyphenylglycine (MCPG), a metabotropic glutamate receptor (mGluR) antagonist, into the basolateral complex of the amygdala (BLA) on the learning and retention of an emotionally motivated task. Rats received either vehicle or three different doses of MCPG (0.2, or 1.0, or 5.0 μg/0.2μl/side, respectively) bilaterally into the BLA, 5 min before they were trained in a continuous multiple-trial inhibitory avoidance (CMIA) task. Response latencies during the training were recorded. Retention was assessed 8 days later. MCPG in the doses given did not significantly affect the acquisition of the CMIA task. However, MCPG at a dose of 5.0 μg/0.2 μl/side impaired the long-term retention test performance. Additionally, a nociception test indicated that dose of MCPG infused into the BLA did not affect the footshock sensitivity. Our results indicate that MCPG, when infused into the BLA of rats prior to the training, impaired long-term memory of aversive training without affecting acquisition.