Effect of destruction of the 5-hydroxytryptaminergic pathways on behavioural timing and “switching” in a free-operant psychophysical procedure |
| |
Authors: | S S A Al-Zahrani M -Y Ho D N Velazquez Martinez M Lopez Cabrera C M Bradshaw E Szabadi |
| |
Institution: | (1) Department of Psychiatry, University of Nottingham, Queen’s Medical Centre, NG7 2UH Nottingham, UK;(2) Present address: Faculty of Psychology, National University of Mexico, 04510 Mexico, DF, Mexico;(3) Present address: Faculty of Medicine, National University of Mexico, 04510 Mexico, DF, Mexico |
| |
Abstract: | This experiment examined the effect of destruction of the ascending 5-hydroxytryptaminergic (5HTergic) pathways on performance
in a free-operant timing schedule. Rats received either injections of 5,7-dihydroxytryptamine into the dorsal and median raphe
nuclei or sham lesions. They were trained to press levers for a sucrose reinforcer. Training sessions consisted of 40, 50-s
trials in which reinforcers were available on a variable-interval 25-s schedule; in the first 25 s of each trial, reinforcers
were only available for responses on lever A, where in the last 25 s reinforcers were available only for responses on lever
B. Data were collected probe trials (four per session) in which no reinforcers were delivered, during the last ten of 50 training
sessions. Both groups showed decreasing response rates on lever A and increasing response rates on lever B as a function of
time from the onset of the trial. Response rate on lever B, expressed as a percentage of overall response rate, could be described
by a two-parameter logistic function; neither the indifference point (i.e the time corresponding to 50% responding on lever
B) nor the slope of the function differed between the two groups. However, the lesioned group showed a higher rate of switching
between response alternatives than the sham-lesioned group. The levels of 5HT and 5-hydroxyindoleacetic acid were reduced
in the brains of the lesioned rats, but the levels of noradrenaline and dopamine were not significantly altered. The results
confirm previous findings that behaviour in timing schedules is sensitive to destruction of the central 5HTergic pathways,
and suggest that these pathways may contribute to the inhibitory regulation of switching between behavioural states. |
| |
Keywords: | 5-Hydroxytryptamine 5 7-Dihydroxytryptamine Operant behaviour Timing Behavioural switching |
本文献已被 SpringerLink 等数据库收录! |
|