title: Involvement of AMPA receptors in maintenance of memory for a passive avoidance task in day-old domestic chicks (Gallus domesticus).
abstract: Day-old chicks (Gallus domesticus) were trained on a one-trial passive avoidance task where the aversive stimulus was an unpleasant tasting substance, methyl anthranilate. Chicks were killed 6.5 h after training. The kinetic parameters of [3H] alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid ([3H]AMPA) binding were determined using quantitative receptor autoradiography and Scatchard analyses in 15 discrete forebrain regions of trained and control (water-trained) chicks, revealing two components of binding in each. KD values showed some regional variation, but were 22.2 +/- 1.1 nmol l-1 for the high-affinity component and 685 +/- 25 nmol l-1 for the low-affinity component of binding to whole forebrain sections from control chicks. Analyses also revealed that Hill coefficients were significantly less than 1 in all regions measured. A significant decrease in KD for the low-affinity component occurred bilaterally in the intermediate and medial hyperstriatum ventrale (IMHV; left, 34.8%; right, 33.3%), a region that has previously been shown to be implicated in the processes of memory formation, following passive avoidance training. A significant decrease in KD for the high-affinity component occurred in the right palaeostriatum augmentatum (19.5%). Significant decreases in Bmax accompanied the KD alterations in both cases. Additionally, bilateral intracerebral injections (administered 4.5-5.5 h after training) into the IMHV of 500 nmol l-1 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a selective antagonist of non-NMDA glutamate receptors (particularly AMPA receptors), resulted in amnesia for one-trial passive avoidance training in day-old chicks tested 6.5 h after training.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Brain and Behaviour Research Group, Open University, Milton Keynes, UK.
authors.forename: R J
authors.initials: RJ
authors.lastname: Steele
authors.forename: M G
authors.initials: MG
authors.lastname: Stewart
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001345:Autoradiography; D001362:Avoidance Learning / Q000502:physiology*; D002645:Chickens; D003720:Densitometry; D005260:Female; D007267:Injections; D007700:Kinetics; D008297:Male; D008568:Memory / Q000502:physiology*; D016548:Prosencephalon / Q000378:metabolism; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000502:physiology*; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000378:metabolism
chemical_list: D018091:Receptors, AMPA; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid