Behavioral analysis of anorexia produced by hindbrain injections of AMPA receptor antagonist NBQX in rats.
The caudal brain stem integrates short-term feedback signals from the oral cavity and the food-handling abdominal viscera, as well as long-term homeostatic, cognitive, and emotional signals from the forebrain, to control ingestive behavior. Glutamate, acting on various receptor subtypes, plays a prominent role in this integrative process. Fourth ventricular injection of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/kainate receptor blocker 1,2,3,4-tetrahydro-6-nitro-2,3-dioxobenzo[f]quinoxaline-7-sulfonamide (NBQX, 0.5-5 nmol/3 microl) dose dependently suppressed intake of 15% sucrose in food-deprived and non-food-deprived rats compared with saline injection. Two consecutive paired NBQX injections (5 nmol) into the fourth ventricle did not produce conditioned taste aversion to saccharin, but LiCl did. Intraburst lick rate and lick efficiency were not affected, but burst size and number and initial lick rate were significantly decreased by NBQX. Local injection of NBQX (2 nmol) into and near the nucleus tractus solitarius also suppressed sucrose intake. These results suggest a general role for non-N-methyl-D-aspartate receptors in the transmission of positive (feedforward) signals, but do not identify the exact processing step involved, such as taste input, sensory-motor processing, or descending facilitation. More localized injections and response measures will be necessary.
Zheng
Huiyuan
H
Pennington Biomedical Research Center, Baton Rouge, Louisiana 70808, USA.
Patterson
Christiane
C
Berthoud
Hans-Rudolf
HR
D000818:Animals; D000855:Anorexia / Q000139:chemically induced / Q000503:physiopathology*; D001362:Avoidance Learning / Q000187:drug effects; D001522:Behavior, Animal / Q000187:drug effects; D019422:Dietary Sucrose / Q000494:pharmacology; D004326:Drinking / Q000187:drug effects; D004435:Eating / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D005247:Feeding Behavior / Q000187:drug effects; D020546:Fourth Ventricle; D018698:Glutamic Acid / Q000378:metabolism; D007276:Injections, Intraventricular; D008297:Male; D011810:Quinoxalines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors* / Q000378:metabolism; D012527:Satiation / Q000187:drug effects; D017552:Solitary Nucleus / Q000503:physiopathology*; D013649:Taste
D019422:Dietary Sucrose; D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; D018091:Receptors, AMPA; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D018698:Glutamic Acid