[Abstract Title]. - Society for Neuroscience

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Title: Dopamine modulates the input from globus pallidus to thalamic reticular nucleus via
presynaptic D4 receptos
Authors: D. GASCA 1 , A. HERNÁNDEZ 1,2 , A. SIERRA 1 , R. VALDIOSERA 1 , B. FLORÁN 1 ,
D. ERLIJ 1 , *J. ACEVES 1 ;
1 Dept Physiol Biophy & Neurosci, Ctr. Investigacion Del IPN, Mexico DF 07000, Mexico; 2 Inst.
de Fisiología Celular, UNAM, Mexico D.F., Mexico
Abstract: Thalamic reticular nucleus (TRn) receives dopaminergic afferents from substantia
nigra pars compacta (SNc) and GABAergic afferents from globus pallidus in the rat. In addition,
D1 and D4 dopamine receptors are expressed in the TRn. Our laboratory previously has shown
that D4 dopamine receptors inhibit the depolarization-induced [H 3 ]GABA release in TRn slices
(Florán et al., 2004a), suggesting a presynaptic modulation of the GABAergic transmission. Here
we have studied the source of the inhibitory synaptic currents modulated by D4 dopamine
receptors in TRn slices from neonatal (14-21 days) rats.
The inhibitory postsynaptic currents were evoked by local electrical stimulation (eIPSCs) in the
presence of CNQX and AP-5. The miniature inhibitory posynaptic currents (mIPSCs) were
recorded in the presence of TTX. At the end of the experiments the synaptic currents were
blocked by bicuculline, confirming their GABAergic nature.
The amplitude of the eIPSCs was reduced 40% by PD168,077 (selective D4 agonist) and this
effect was blocked by L-745870 (selective antagonist). This effect was accompanied by a 23%
increase in the paired pulse ratio, indicating a presynaptic effect. It was also observed that
PD168,077 reduced by 40% the frequency of the mIPSCs without affecting their amplitude. This
effect was blocked by L-745870, indicating that it was mediated by a specific activation of D4
dopamine receptors. Dopamine also inhibited both eIPSCs and mIPSCs, and the inhibition was
blocked by L-745,870. These results together indicate a dopamine modulation of GABAergic
synaptic transmission by presynaptic D4 dopamine receptors in the TRn. Previous lesion of the
globus pallidus eliminated completely the effect of the activation of D4 dopamine receptors on
the GABAergic transmission, judged by its effect on evoked or spontaneous IPSCs. These results
indicate that D4 dopamine receptors are located on the GABAergic pallidal terminals in the TRn,
where they modulate the pallidal input.
Disclosures: D. Gasca, None; J. Aceves , None; A. Hernández, None; A. Sierra, None; R.
Valdiosera, None; B. Florán, None; D. Erlij, None.
Poster
274. Basal Ganglia: Transmitters and Neuromodulation II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm