[Abstract Title]. - Society for Neuroscience

Abstract: Immunocytochemical studies have been shown the presence of D4 receptors in
substantia nigra pars reticulate (SNr). On the other hand, it is known that neurons of the globus
pallidus (GP) express mRNA coding for D4. Taking this into consideration we have here
explored the modulation of GABA release by D4 receptors assumed to be located on pallidal
terminals in SNr. We studied the effect of dopamine and D4 selective agonists and antagonist on
[ 3 H]GABA release from depolarized (20 mM K + ) SNr slices. To avoid endogenous dopamine
effects, the slices were isolated from reserpinized rats. A set of experiments were performed on
slices from rats with a previous kainic acid-induced lesion of either the globus pallidus or the
caudate-putamen to test the location of the receptors on pallidal or striatal terminals.
In reserpinized slices PD 168,077, a selective D4 agonist, and dopamine dose-dependently
inhibited GABA release (log EC50= -9.27±0.24 and -5.96±0.42 respectively), and their effect
was antagonized by L-745,870 (100 nM). To prevent activation of D1 receptors by dopamine,
the effect of dopamine was tested in presence of SCH 23390. The effect of PD 168,077 was lost
in slices from GP lesioned rats, but the effect remained on slices from the intact side of the same
animal. By contrast, the inhibitory effect of PD 168,077in slices from striatal-lesioned rats
persisted, although the facilitation of GABA release by the activation of D1 receptors with SKF
38393 was lost in these slices, indicating the loss of most of the striatonigral terminals. These
results suggest that the D4 receptors modulating GABA release in SNr are located exclusively on
pallido-nigral terminals.
The present results signal the role of D4 receptors in the output nucleus of the basal ganglia. By
modulating the input from the globus pallidus to the output nuclei, they may play a relevant role
in the control of movement and other functions processed by the basal ganglia.
Disclosures: J. Acosta, None; A. Sierra, None; R. Escartin-Perez , None; D. Erlij, None; J.
Aceves, None; B. Floran, None.
Poster
275. Posture: Kinematics and Muscle Activity
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 275.1/JJ16
Topic: D.16.d. Kinematics and Muscle Activity
Support: NHMRC Project Grant 456017
Title: Change in anticipatory postural adjustments in novel and familiar tasks
Authors: *L. M. HALL, S. G. BRAUER, P. W. HODGES;
Univ. Queensland, Brisbane, Australia