Distinct commissural pathways are involved in the enhanced release of dopamine induced in the contralateral caudate nucleus and substantia nigra by unilateral application of GABA in the cat thalamic motor nuclei.
The effects of diencephalic or telencephalic commissural sectioning on the changes in [3H]dopamine ([3H]DA) release from nerve terminals (in the caudate nucleus, CN) and dendrites (in the substantia nigra, SN) of the two nigro-striatal dopaminergic pathways induced by the application of GABA (10(-5) M, 30 min) into the left ventralis medialis (VM) or ventralis lateralis (VL) thalamic nuclei were investigated. Experiments were performed in halothane-anesthetized cats implanted with push-pull cannulae in both CN and SN. In unlesioned cats, GABA application into the left VM-VL increased [3H]DA release in both CN and in the contralateral SN confirming previous results. Sectioning of the thalamic massa intermedia only blocked the GABA-induced increase in [3H]DA release in the contralateral SN, the responses in both CN being preserved. Sectioning of the rostral part of the corpus callosum only prevented the GABA-induced increase in [3H]DA release in the contralateral CN, whereas [3H]DA release in the ipsilateral CN and in the contralateral SN was still enhanced. These results suggest that changes in [3H]DA release evoked in both CN and in the contralateral SN by GABA application into the left VM-VL might involve different mechanisms: those observed in the CN result from potent pre-synaptic influences mediated by the bilateral cortico-striatal projections; those induced in the contralateral SN are due to other types of messages involving or passing through the thalamic massa intermedia.
D000818:Animals; D002415:Cats; D002421:Caudate Nucleus / Q000187:drug effects / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D007839:Functional Laterality; D008297:Male; D009928:Organ Specificity; D013238:Stereotaxic Techniques; D013378:Substantia Nigra / Q000187:drug effects / Q000502:physiology*; D013787:Thalamic Nuclei / Q000187:drug effects / Q000502:physiology*; D014316:Tritium; D014443:Tyrosine / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D014316:Tritium; D014443:Tyrosine; D005680:gamma-Aminobutyric Acid; D004298:Dopamine