Metabotropic glutamate receptor 5 in conditioned taste aversion learning

• Published in: Neurobiology of learning and memory Vol. 92; no. 3; pp. 460 - 463
• Main Authors: Simonyi, A., Serfozo, P., Parker, K.E., Ramsey, A.K., Schachtman, T.R.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.10.2009; Elsevier; Elsevier BV
• Subjects: Acquisition; Amygdala; Amygdala - drug effects; Amygdala - physiology; Animal cognition; Animal memory; Animals; Avoidance Learning - physiology; Behavioral psychophysiology; Biological and medical sciences; Brain - drug effects; Brain - physiology; Conditioned taste aversion; Conditioning, Classical - physiology; Extinction, Psychological - drug effects; Extinction, Psychological - physiology; Fundamental and applied biological sciences. Psychology; Insular cortex; Male; Metabotropic glutamate receptor 5; Neurobiology; Parietal Lobe - drug effects; Parietal Lobe - physiology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Pyridines - administration & dosage; Pyridines - pharmacology; Random Allocation; Rats; Rats, Sprague-Dawley; Receptor, Metabotropic Glutamate 5; Receptors, Metabotropic Glutamate - antagonists & inhibitors; Receptors, Metabotropic Glutamate - metabolism; Saccharin - administration & dosage; Sensory perception; Sweetening Agents - administration & dosage; Taste; Taste Perception - physiology; Temporal Lobe - drug effects; Temporal Lobe - physiology; Thiazoles - administration & dosage; Thiazoles - pharmacology; Time Factors; Conditioned taste aversion; Amygdala; Metabotropic glutamate receptor 5; Insular cortex; Acquisition; Central nervous system; Basal ganglion; Glutamate receptor; Gustative system; Encephalon; Learning; Acquisition process; Metabotropic receptor; Gustation; Taste; Conditioned aversion; Amygdaloid nucleus
• ISSN: 1074-7427; 1095-9564
• DOI: 10.1016/j.nlm.2009.05.002

In conditioned taste aversion (CTA), animals learn to avoid a flavored solution (conditioned stimulus, CS) previously paired with internal malaise (unconditioned stimulus, US). Metabotropic glutamate receptor 5 (mGlu5) has been implicated in learning and memory processes and is necessary for CTA. In the present study, local microinjections of a mGlu5-selective antagonist, 3-[2-methyl-1,3-thiazol-4yl)ethynyl]pyridine (MTEP, 0, 1 or 5 μg) into the insular cortex and basolateral amygdala were used in male, Sprague-Dawley rats to examine the role of mGlu5 receptors in the encoding of taste memory. MTEP was infused 20 min before saccharin intake during CTA conditioning. MTEP injection into the basolateral amygdala resulted in robust CTA, similar to the vehicle-treated animals but slowed extinction; that is, MTEP enhanced CTA. MTEP injection into the insular cortex resulted in an increased saccharin intake on the conditioning trial, which potentially influenced the performance on the test trials; MTEP had no effect on CTA learning when controlled access to saccharin was used on the conditioning trial. These results indicate that mGlu5 receptors are involved in taste memories in a region-specific manner.