[Abstract Title]. - Society for Neuroscience

Poster
274. Basal Ganglia: Transmitters and Neuromodulation II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 274.15/JJ10
Topic: D.15.a. Transmitters and neuromodulation
Support: CONACyT Grant 50427Q
Title: Dopamine modulates via D4 receptors pallido-nigral transmision to sustantia nigra
Authors: *R. CRUZ-TRUJILLO 1 , A. SIERRA 2 , R. VALDIOSERA 2 , D. ERLIJ 3 , B.
FLORAN 2 , J. ACEVES 2 ;
1 CINVESTAV IPN, Mexico, D.F., Mexico; 2 CINVESTAV-IPN, Mexico DF, Mexico; 3 Sunny
Dowstate Med. Center, State Univ. of NY, New York, NY
Abstract: Inmunocytochemical studies have been shown the presence of D4 receptors in the rat
sustantia nigra. Lack of mRNA in the nucleus suggested that D4 receptors are located on
afferents. mRNA for D4 receptor is expressed in the globus pallidus, so it is possible that the
receptors are located on pallidal afferents to sustantia nigra. Here we have examined this
assumption using whole-cell recordings of visualized SNr neurons from neonatal (14-21days)
rats. To test the source of the afferents some experiments were done in slices from rats lesioned
unilaterally with ibotenic acid in the globus pallidus. Spontaneous miniature inhibitory synaptic
currents (mIPSCs) were recorded in the presence of TTX, CNQX and D-AP5, to block
propagated action potentials and participation of glutamatergic mEPSCs. Bicuculline abolished
the mIPSCs, indicating their GABAergic nature. Experiments were performed in the presence of
SCH 23390 to block D1 receptors from striato-nigral afferents. Addition of dopamine reduced by
31.56% the frequency of the mIPSCs without affecting their amplitude, indicating a presynaptic
locus of the involved receptors. The selective D4 agonist, PD 168,077 also reduced the
frequency (30.56 %), and, as dopamine, without modifying the amplitude of the mIPSCs. The
effect of dopamine and PD168 077 was blocked by L-745,870, a selective D4 antagonist. In
slices from lesioned rats, the effect of PD 168,077 was lost. These results indicate that dopamine
modulates the GABAergic transmission in the SNr via activation of D4 receptors located on the
GABAergic terminals from globus pallidus origin. Through this action, dopamine may control
ADHD, where D4 receptors appear to be involved, and which is controlled by elevating the
levels of endogenous dopamine by blocking its capture either with amphetamine or
methylphenidate.
Disclosures: R. Cruz-Trujillo , None; A. Sierra, None; R. Valdiosera, None; D. Erlij,
None; B. Floran, None; J. Aceves, None.