چكيده لاتين :
Mediodorsal (MD) thalamic nucleus, which is considered to take place between extra pyramidal
and limbic feedback circuit, receives projective fibers from ventrolateral neurons of reticular part of substantia
nigra (SNr). In order to better understand the influence and chemical reaction of these fibers upon MD
nucleus, the morphology and synaptology of them were examined in the present study. Methods: Phaseolous
vulgaris-Ieucoagglutin (PHA-L) was injected into substantia nigra pars reticulate. After 3-4 days, the sections
of SNr injection site and MD nucleus were prepared. Then, we examined organization, morphology and,
synaptology of PHA-L labeled SNr fibers that go to caudal and lateral part of MD thalamic nucleus. Results:
At the electron microscopic level, the SNr terminals made synapses predominantly with the medium to small
dendrites and far less frequently with soma and large dendrites. These terminals were packed with
polymorphic synaptic vesicles and formed symmetrical synapses; furthermore, it has been already recognized
that cortico straital fibers from sensory-motor cortex go to region of the SNr that give rise to the nigrothalamic
fibers. Conclusion: This data suggest that upon the synaptic organization, morphology and chemical nature of
GABAergic, SNr fibers may have different inhibitory influence on MD neurons regulating the thalamic output
from MD to cerebral cortex in the control of limbic and extra pyramidal feedback system. Iran. Biomed. 1. 12
(4): 209-215, 2008
