| Our previous studies confirmed that the central pathway of trigeminal proprioceptive sensation consists of four orders of neurons, and neurons from the first- to the fourth-order are located, respectively, in the mesencephalic trigeminal nucleus(Vme), the dorsomedial part of the subnucleus oralis of the spinal trigeminal nucleus and its adjacent reticular formation(Vodm-LRF), the "zone-shaped area" [including the caudolateral part of the supratrigeminal nucleus (Vsup-CL), the dorsomedial part of the principal sensory trigeminal nucleus(Vpdm), the area ventral to the motor trigeminal nucleus (AVM) and the area dorsal to the superior olivary nucleus (ADO)] and the contralateral ventral posteromedial nucleus (VPM) of the thalamus. Because the pathway is a novel one, there has been little systematic morphological data available so far regarding the neurotransmitters involved in this pathway.Parvalbumin (PV) is an important member of the family of calcium-binding proteins which has a high affinity for binding Ca2+, and widely distributed in central nervous system. Although its function is not known completely, PV may play important roles in the axonal flow, cell metabolism and synaptic transmission through binding with Ca2+. Ourprevious studies showed that PV is distributed densely in the relay nuclei on the central four orders pathway of the trigeminal proprioceptive sensation and there are approximately 30-50% of PV-LI neurons projected to VPM of the thalamus in the third-order nuclei. But how about the morphological feature and the relationship between the PV-LI and other neurons in the second-/third-order relay nuclei. What the synaptic connection between the PV-LI and the neurons projecting to the thalamus.It is well known that glutamate (Glu) is a major excitatory neurotransmitter in mammalian CNS. Glu of CNS mainly comes from glutamine and phosphate activated glutaminase (PAG) can decomposed the glutamine to Glu and ammonia and is the main source of the Glu of the CNS, so PAG is used as the special marker of glutaminergic neurons. Recently, a noval brain-specific Na^-dependent inorganic phosphate transporters was successfully cloned using the method of molecular biology and was named DNPI because they had the characters of the vesicular glutamate transporter (VGluT). Some studies showed that DNPI were distributed extensively in the brain area where Glu was used as the neurotransmitter, such as thalamus, medulla oblongata and spinal cord. The ultrastructural studies indicated that most of DNPI are located in the presynaptic terminals and distributed on the synaptic vesicular membrane. So, DNPI were regarded as the specific marker of the brain glutaminergic terminals. In addition, there were also some GABAergic terminals in the "Zone-shaped area" according to our previous studies. But there are still no reports about the relationships of DNPI-like and GABAergic immunoreactive ( GAD-LI ) terminals with PAG-like immunoreactive (PAG-LI)neurons in "Zone-shaped area".To answer these questions, we observed systemically the synaptic connections among the PV-like immunoreactive neurons, fibers and terminalsand the connections between DNPI-like, GABAergic terminals and PAG-LI neurons using the methods of electron microscopic imrnunohistochemistry, triple-immunofluorescence histochemistry and retrograde tracing method combined with pre-embeded immunoelectron microscopic double-labeled technique.Part IThe Electron Microscope Study of the Synaptic Connections ofPan albumin-like Immunopositive Structure in the Second-/Third-Nuclei on the Central Pathway of the TrigeminalProprioceptive Sensation of the RatThe present study examined that the synaptic connections of PV-like immunoreactive (PV-LI) neuronal cell bodies, fibers and terminals on the second-/third-order nuclei of this pathway by using electron microscopic immunohistochemical method. The results are following:1.There are a lot of PV-LI dendrites and axonal terminals in the Vodm-LRF and "Zone-shaped area" including...
|
PDF Full Text Request