Journal of Neuroscience, Vol 6, 2037-2044, Copyright © 1986 by Society for Neuroscience
Bilateral augmentation of dopaminergic and serotonergic activity in the striatum and nucleus accumbens induced by conditioned circling
C Szostak, A Jakubovic, AG Phillips and HC Fibiger
The involvement of dopaminergic (DA) and serotonergic (5-HT) systems in
circling was assessed by determining the neurochemical correlates of
circling induced and maintained by two different schedules of water
reinforcement. The conditioned circling paradigm was employed in an attempt
to replicate reports that levels of DA and 3,4- dihydroxyphenylacetic acid
(DOPAC) were increased in the striatum and nucleus accumbens septi (NAS)
contralateral to the direction of circling. Rats trained to circle using a
continuous schedule of reinforcement did not exhibit any changes in
concentrations of DA, DOPAC, or homovanillic acid (HVA). Bilateral
increases in 5-HT concentrations were observed in the striatum. Use of an
intermittent schedule of reinforcement (FR-2) produced higher rates of
circling. In rats maintained on the FR-2 schedule, no changes in DA or its
metabolites were observed in the striatum. The ratio of HVA to DA was,
however, increased bilaterally, suggesting a bilateral augmentation of DA
utilization. Concentrations of DA were lower in the NAS contralateral to
direction of turning. While NAS levels of HVA were elevated bilaterally
when compared to non-circling controls, HVA was lower in the NAS
contralateral to the direction of circling. DA utilization, as estimated by
HVA: DA ratios, was increased bilaterally in the NAS. None of the measures
of DA activity within the olfactory tubercle (OT) were influenced by
circling. Turnover of 5-HT, as estimated by the ratio of 5-HT to
5-hydroxyindoleacetic acid (5-HIAA), was increased bilaterally in the
striatum, NAS, and OT.(ABSTRACT TRUNCATED AT 250 WORDS)