Wakoto Matsuda

Single Nigrostriatal Dopaminergic Neurons Form Widely Spread and Highly Dense Axonal Arborizations in the Neostriatum

The axonal arbors of single nigrostriatal dopaminergic neurons were visualized with a viral vector expressing membrane-targeted green fluorescent protein in rat brain. All eight reconstructed tyrosine hydroxylase-positive dopaminergic neurons possessed widely spread and highly dense axonal arborizations in the neostriatum. All of them emitted very little axon collateral arborization outside of the striatum except for tiny arborization in the external pallidum. The striatal axonal bush of each reconstructed dopaminergic neuron covered 0.45–5.7% (mean ± SD = 2.7 ± 1.5%) of the total volume of the neostriatum. Furthermore, all the dopaminergic neurons innervated both striosome and matrix compartments of the neostriatum, although each neurons arborization tended to favor one of these compartments. Our findings demonstrate that individual dopaminergic neurons of the substantia nigra can broadcast a dopamine signal and exert strong influence over a large number of striatal neurons. This divergent signaling should be a key to the function of the nigrostriatal system in dopamine-based learning and suggests that neurodegeneration of individual nigral neurons can affect multiple neurons in the striatum. Thus, these results would also contribute to understanding the clinicopathology of Parkinsons disease and related syndromes.

Exclusive and common targets of neostriatofugal projections of rat striosome neurons: a single neuron-tracing study using a viral vector

The rat neostriatum has a mosaic organization composed of striosome/patch compartments embedded in a more extensive matrix compartment, which are distinguished from each other by the input–output organization as well as by the expression of many molecular markers. The matrix compartment gives rise to the dual γ‐aminobutyric acid (GABA)ergic striatofugal systems, i.e. direct and indirect pathway neurons, whereas the striosome compartment is considered to involve direct pathway neurons alone. Although the whole axonal arborization of matrix striatofugal neurons has been examined in vivo by intracellular staining, that of striosome neurons has never been studied at the single neuron level. In the present study, the axonal arborizations of single striosome projection neurons in rat neostriatum were visualized in their entirety using a viral vector expressing membrane‐targeted green fluorescent protein, and compared with that of matrix projection neurons. We found that not only matrix but also striosome compartments contained direct and indirect pathway neurons. Furthermore, only striatonigral neurons in the striosome compartment projected directly to the substantia nigra pars compacta (SNc), although they sent a substantial number of axon collaterals to the globus pallidus, entopeduncular nucleus and/or substantia nigra pars reticulata. These results suggest that striosome neurons play a more important role in the formation of reward‐related signals of SNc dopaminergic neurons than do matrix neurons. Together with data from previous studies in the reinforcement learning theory, our results suggest that these direct and indirect striosome–SNc pathways together with nigrostriatal dopaminergic neurons may help striosome neurons to acquire the state‐value function.

Levodopa treatment for patients in persistent vegetative or minimally conscious states

The persistent vegetative state (PVS) and the minimally conscious state (MCS) are conditions of altered consciousness after severe brain damage due to a variety of pathologies. However, the specific pathophysiological mechanisms and a therapeutic strategy for intervention have not as yet been established. We review previous reports of levodopa treatment for patients in PVS, MCS, or other mental disorders, and have focused on five representative cases: four of PVS and one of MCS after severe brain injury. In summary, our review suggests the effectiveness of levodopa treatment is probably dependent upon the following criteria: (1) Diagnosis of PVS or MCS as distinct from other related conditions, (2) Concomitant symptoms of parkinsonism, and (3) Concomitant neuroradiological findings of high intensity lesions in the dopaminergic pathway on T2 weighted MRI. The apparent success of levodopa in the five cases described may reflect a specific subgroup of PVS and MCS patients, where the administration of levodopa is effective. However, we should not regard PVS or MCS as a single entity, since levodopa is unlikely to be effective in all cases. Therapeutic strategies should aim to identify the key pathophysiological mechanism for each patient and target interventions accordingly.

Targeting green fluorescent protein to dendritic membrane in central neurons.

Dendritic and axonal processes are input and output sites, respectively, of neuronal information, and detailed visualization of these processes may be indispensable for elucidating the neuronal circuits and revealing the principles of neuronal functions. To establish a method for completely visualizing dendritic processes, we first developed green fluorescent protein (GFP)-based proteins and, by using lentivirus with a neuron-specific promoter, examined whether or not the protein fully visualized the dendritic processes of infected neurons. When GFP with a palmitoylation (palGFP) or myristoylation/palmitoylation site (myrGFP) was expressed in rat brain with lentiviruses, myrGFP labeled dendritic membrane better than palGFP. Subsequently, dendrite-targeting efficiencies of three basolateral membrane-sorting and three putative dendrite-targeting domains, which were attached to myrGFP C-terminus, were examined in striatonigral GABAergic and corticothalamic glutamatergic neurons, and in cultured cortical neurons. Of the six domains, C-terminal cytoplasmic domain of low density lipoprotein receptor (LDLRct) was most efficient in targeting the protein to dendrites, showing 8.5-15-fold higher efficiency in striatonigral neurons compared with myrGFP. Finally, dendritic membrane-targeting potency of myrGFP-LDLRct was confirmed in transgenic mice using Thy1 or Gad1 expression cassette. Thus, myrGFP-LDLRct is an excellent synthetic protein for dendritic visualization, and may be a useful tool for the morphological analysis of neuronal circuits.

Delayed onset of posttraumatic acute subdural hematoma after mild head injury with normal computed tomography: a case report and brief review.

Delayed intracranial hematomas are one of the most efficiently remedied causes of secondary brain insult if identified early but can cause significant disability or death if not promptly recognized and treated. Occasional reports or reviews have documented cases of delayed posttraumatic intracerebral hematoma or subdural/epidural hematoma. Since the development of neuroradiology, computed tomography (CT) scanning in particular has revealed that delayed intracerebral or epidural hematomas after head injury and/or decompression surgery are more common than had been previously suspected. However, delayed posttraumatic subdural hematoma is rarely reported. Here, we report a case of delayed onset of posttraumatic acute subdural hematomas after mild head injury in a patient with CT findings that did not disclose anything abnormal. We also briefly review the pertinent literature and discuss the pathogenesis of delayed onset.

Correlative analysis of immunoreactivity in confocal laser-scanning microscopy and scanning electron microscopy with focused ion beam milling.

Recently, three-dimensional reconstruction of ultrastructure of the brain has been realized with minimal effort by using scanning electron microscopy (SEM) combined with focused ion beam (FIB) milling (FIB-SEM). Application of immunohistochemical staining in electron microscopy (EM) provides a great advantage in that molecules of interest are specifically localized in ultrastructures. Thus, we applied immunocytochemistry for FIB-SEM and correlated this immunoreactivity with that in confocal laser-scanning microcopy (CF-LSM). Dendrites of medium-sized spiny neurons in the rat neostriatum were visualized using a recombinant viral vector, which labeled the infected neurons with membrane-targeted GFP in a Golgi stain-like fashion. Moreover, the thalamostriatal afferent terminals were immunolabeled with Cy5 fluorescence for vesicular glutamate transporter 2 (VGluT2). After detection of the sites of terminals apposed to the dendrites by using CF-LSM, GFP and VGluT2 immunoreactivities were further developed for EM by using immunogold/silver enhancement and immunoperoxidase/diaminobenzidine (DAB) methods, respectively. In contrast-inverted FIB-SEM images, silver precipitations and DAB deposits were observed as fine dark grains and diffuse dense profiles, respectively, indicating that these immunoreactivities were as easily recognizable as those in the transmission electron microscopy (TEM) images. Furthermore, in the sites of interest, some appositions displayed synaptic specializations of an asymmetric type. Thus, the present method was useful in the three-dimensional analysis of immunocytochemically differentiated synaptic connections in the central neural circuit.

A single-neuron tracing study of arkypallidal and prototypic neurons in healthy rats

The external globus pallidus (GP) is known as a relay nucleus of the indirect pathway of the basal ganglia. Recent studies in dopamine-depleted and healthy rats indicate that the GP comprises two main types of pallidofugal neurons: the so-called “prototypic” and “arkypallidal” neurons. However, the reconstruction of complete arkypallidal neurons in healthy rats has not been reported. Here we visualized the entire axonal arborization of four single arkypallidal neurons and six single prototypic neurons in rat brain using labeling with a viral vector expressing membrane-targeted green fluorescent protein and examined the distribution of axon boutons in the target nuclei. Results revealed that not only the arkypallidal neurons but nearly all of the prototypic neurons projected to the striatum with numerous axon varicosities. Thus, the striatum is a major target nucleus for pallidal neurons. Arkypallidal and prototypic GP neurons located in the calbindin-positive and calbindin-negative regions mainly projected to the corresponding positive and negative regions in the striatum. Because the GP and striatum calbindin staining patterns reflect the topographic organization of the striatopallidal projection, the striatal neurons in the sensorimotor and associative regions constitute the reciprocal connection with the GP neurons in the corresponding regions.

Right hepatic artery traveling anteriorly to the common bile duct

The topographic relationship between arteries and hepatobiliary ducts can be crucial during cholecystectomy. We observed the right hepatic artery traveling a rare route in a 91-year-old male. The common hepatic artery gave off the left hepatic, the right gastric, the gastroduodenal, and the right hepatic arteries consecutively without forming the proper hepatic artery. The right hepatic artery crossed the common bile duct anteriorly, ascended on the right side of the duct, passed the cystic duct posteriorly, and entered the right lobe of the liver. The so-called 9 o’clock artery running on the right side of the common hepatic and common biliary is reasonably speculated to be the aberrant right hepatic artery as presently shown. Developmental and clinical issues are discussed.

Excision of Juvenile Pilocytic Astrocytoma of the Midbrain after Radiotherapy

A 13-year-old girl presented with consciousness disturbance, right hemiparesis, and impairment of hearing, swallowing, and ocular movements. A magnetic resonance image demonstrated marked hydrocephalus due to a large cystic tumor (40 × 40 × 30 mm) in the midbrain. Emergency ventricular drainage and stereotactic cyst puncture dramatically improved her condition. Since her family did not agree to surgery on the brain stem, radiotherapy was performed after ventriculoperitoneal shunting. Conventional radiotherapy of 50.4 Gy was temporarily effective, and the growth of the tumor was stabilized until approximately 8 months later when regrowth was noticed. At this stage, with the consent of her family, the tumor was removed via an infratentorial supracerebellar approach. The pathological diagnosis was juvenile pilocytic astrocytoma. The postoperative course was uneventful. No recurrence has been observed during the follow-up period of more than 6 years. This case study shows that initial excision may be appropriate for some low-grade focal lesions in the midbrain when the histological diagnosis and consent have been obtained.

Effects of environmental enrichment on the activity of the amygdala in micrencephalic rats exposed to a novel open field: Fos activation in micrencephalic rats

Environmental enrichment (EE) mediates recovery from sensory, motor, and cognitive deficits and emotional abnormalities. In the present study, we examined the effects of EE on locomotor activity and neuronal activity in the amygdala in control and methylazoxymethanol acetate (MAM)‐induced micrencephalic rats after challenge in a novel open field. Control rats housed in EE (CR) showed reduced locomotor activity compared to rats housed in a conventional cage (CC), whereas hyperactivity was seen in MAM rats housed in a conventional cage (MC) and in MAM rats housed in EE (MR).