ABSTRACT
Individual differences in water maze and open-field performance of aged and adult rats were compared in a cross-sectional study. Three- and 24-month-old rats were classified into superior, moderate, and inferior groups on the basis of escape latencies during hidden platform acquisition and were compared regarding water maze acquisition and extinction, and open-field behavior. Unexpectedly, subgroup differences were invariant across age: The inferior and superior maze learners differed in (a) thigmotactic swimming during water maze acquisition and extinction and (b) open-field rearings. Thus, although aging has a detrimental effect on water maze acquisition and extinction, the degree of impairment might be partly determined by individual novelty-induced rearing activity and thigmotactic swimming at adult ages.
Subject(s)
Aging/psychology , Escape Reaction , Maze Learning , Age Factors , Animals , Extinction, Psychological , Male , Rats , Rats, Wistar , Reaction Time , WaterABSTRACT
Substance P (SP) has memory-promoting, reinforcing and anxiolytic-like effects when applied systemically or centrally. Such effects may be mediated by the neurokinin-1 (NK-1) receptor, since SP preferentially binds to this receptor. We measured the effects of a selective non-peptide NK-1 receptor antagonist, SR140333 (1, 3 and 9 mg/kg i.p.) on ACh levels in frontal cortex, amygdala and hippocampus by microdialysis and HPLC. Levels of ACh in the hippocampus increased dose-dependently immediately after treatment. The same doses of SR140333 given post-trial had minor facilitative effects on inhibitory avoidance learning and open-field habituation, but did not have reinforcing effects in a conditioned place preference (CPP) task. The selective action of NK-1 receptor antagonism on hippocampal ACh may be related to its positive influence on learning.
Subject(s)
Acetylcholine/metabolism , Hippocampus/metabolism , Memory/drug effects , Neurokinin-1 Receptor Antagonists , Piperidines/pharmacology , Quinuclidines/pharmacology , Amygdala/metabolism , Animals , Avoidance Learning , Behavior, Animal , Chromatography, High Pressure Liquid , Dose-Response Relationship, Drug , Hippocampus/drug effects , Injections, Intraperitoneal , Male , Microdialysis , Rats , Rats, Wistar , Spatial Behavior , StereoisomerismABSTRACT
In 80 domestic chickens from 8 breeds, the volumes of 12 brain parts were identified as dimensions in a cluster analysis. Based on Euclidean metrics and the Ward algorithm at least 2 groups were found that are congruent with the breeds 'White Crested Polish chicken' and 'Breda', although the breed identity was not a variable used in the cluster analysis. Domestication is interpreted as evolution which includes the possibility of speciation. It is hypothesized that White Crested Polish chickens and Bredas are becoming new species in terms of a biospecies concept.
