Journal of Neuroscience, Vol 14, 6144-6152, Copyright © 1994 by Society for Neuroscience
Individual locomotor response to novelty predicts selective alterations in D1 and D2 receptors and mRNAs
MS Hooks, JL Juncos, JB Justice Jr, SM Meiergerd, SL Povlock, JO Schenk and PW Kalivas
Department of VCAPP, Washington State University, Pullman 99164-6520.
Rats that have a greater locomotor response to novelty (high responders,
HR) have differences in measures of presynaptic dopamine transmission
compared to low responders (LR) to a novel environment, including altered
dopamine release and behavioral response to indirect dopamine agonists.
This study examined the role of three dopamine terminal fields, the nucleus
accumbens, striatum, and medial prefrontal cortex, in differences between
HR and LR. In the first experiment, dopamine was infused directly into the
nucleus accumbens (0, 3, 10, and 30 micrograms/side) or the striatum (0,
10, 30, and 100 micrograms/side). HR showed a greater behavioral response
to both the 3 and 30 micrograms/side doses infused into the nucleus
accumbens compared to LR. No differences between HR and LR were revealed by
dopamine infusion into the striatum. In the second experiment, radioligand
binding assays were performed to determine if differences exist between
high and low responder rats in the Bmax and/or KD of radiolabeled
antagonist ligands for the dopamine D1 and/or D2 receptors. There were
fewer D2 binding sites in the nucleus accumbens and fewer sites in the
striatum in HR compared to LR. High responders showed a greater Bmax for D1
binding sites in the nucleus accumbens than LR. No differences in number of
binding sites for D1 receptors were observed between HR and LR in the
striatum. No differences between HR and LR in D2 or D1 receptor binding
were observed in the medial prefrontal cortex. There were no differences in
KD for any of the dopamine receptors in the regions examined.(ABSTRACT
TRUNCATED AT 250 WORDS)