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Genetic differences in NMDA and D1 receptor levels, and operant responding for food and morphine in Lewis and Fischer 344 rats.
- Source :
-
Brain research [Brain Res] 2003 May 30; Vol. 973 (2), pp. 205-13. - Publication Year :
- 2003
-
Abstract
- Previously, we have shown that Lewis (LEW) rats acquire faster than Fischer 344 (F344) rats operant food- and morphine-reinforced tasks under fixed-ratio schedules of reinforcement. The first purpose of the present work has been to study if differences in operant responding behavior may participate in the reported differences in morphine self-administration behavior between both inbred rat strains. To this end, we have analyzed the microstructure of responding obtained under a variable-interval (VI) of food reinforcement by calculating the inter-response time (IRT) for each rat strain. LEW rats exhibited shorter IRTs than F344 rats, suggesting that LEW rats may have an inherent high or compulsive operant responding activity. When subjects of both inbred rat strains were submitted to a schedule of morphine reinforcement of high responding requirements such as progressive ratio schedules, LEW rats also reached significantly higher breaking points and final response ratio than F344 rats for i.v. morphine self-administration. Given that there are neurochemical differences between both rat strains and that glutamatergic N-methyl-D-aspartate (NMDA) and dopaminergic D(1) receptors have been involved in operant responding behavior, a second purpose of this work has been to measure basal NMDA and D(1) receptor levels in these rat strains by quantitative receptor autoradiography. Compared to F344 rats, LEW rats showed higher basal NMDA receptor levels in frontal and cingulate cortex, caudate putamen, central amygdaloid nuclei, and intermediate white layer of superior colliculus, and higher basal D(1) receptor levels in several areas of hippocampus and thalamus, and substantia nigra pars reticulata. Taken together, these results suggest that an inherent high operant responding activity of LEW rats may have a role in the previous reported faster acquisition of opiate-reinforced behavior in operant self-administration paradigms under fixed-ratio schedules of reinforcement. In addition, a basal higher NMDA and D(1) receptor levels of LEW rats compared to F344 rats may participate in the neurochemical background that mediates the behavioral differences between both inbred rat strains.
- Subjects :
- Animals
Autoradiography methods
Behavior, Animal
Binding Sites
Brain metabolism
Brain Mapping
Male
Morphine administration & dosage
Narcotics administration & dosage
Rats
Rats, Inbred F344 genetics
Rats, Inbred F344 physiology
Rats, Inbred Lew genetics
Rats, Inbred Lew physiology
Reaction Time
Receptors, Dopamine D1 genetics
Receptors, N-Methyl-D-Aspartate genetics
Reinforcement, Psychology
Self Administration
Species Specificity
Conditioning, Operant
Food
Morphine pharmacology
Narcotics pharmacology
Receptors, Dopamine D1 metabolism
Receptors, N-Methyl-D-Aspartate metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0006-8993
- Volume :
- 973
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Brain research
- Publication Type :
- Academic Journal
- Accession number :
- 12738064
- Full Text :
- https://doi.org/10.1016/s0006-8993(03)02482-x