Harumichi Imai

Microangioarchitecture of rat parietal cortex with special reference to vascular "sphincters". Scanning electron microscopic and dark field microscopic study.

Microangioarchitecture of the rat parietal cortex was studied by means of scanning electron microscopy and dark field microscopy. The richest supply of blood vessels in the parietal cortex was found in layer HI + IV and layer V, where 2 isolated plexuses of microressels were prominent. Tbe appearance of the plexuses was quite different between motor and sensory areas. In the motor area the capillary plexuses were narrow and compact, while in sensory area the plexuses were wide and diffuse. Characteristic ring formations, called ring-shaped-compressions in the present study, were frequently observed at branching sites of arterioles. The ring-shaped-compression probably corresponds to the precapillary sphincter. A similar structure was also seen in capillaries and venules and, therefore, it is likely that not only arterioles, but also capillaries and eren venules, can actively change diameter to control cerebral blood flow.

A Light and Electron Microscopic Immunohistochemical Study of Vasoactive Intestinal Polypeptide— And Substance P-Containing Nerve Fibers along the Cerebral Blood Vessels: Comparison with Aminergic and Cholinergic Nerve Fibers

Vasoactive intestinal polypeptide (VIP)– and substance P–containing nerve fibers were observed in the cerebral blood vessels using an immunohistochemical technique. VIP-containing nerve fibers distributed in a spiral pattern, similar to that of muscle cells. Under electron microscopic observation, VIP-immunoreactive terminals lay close to a muscle cell in the inner layer of the adventitia. In contrast, substance P–containing nerve fibers showed a meshwork pattern in the outer layer of the adventitia. Using both acetylcholinesterase (AChE) staining and VIP immunohistochemistry, AChE-positive and VIP-immunoreactive nerve fibers revealed almost the same distribution in the same specimen. The present data suggest that VIP-containing nerve fibers may play a role in the smooth muscle control of the blood vessels, whereas substance P–containing nerve fibers may not take part in muscle control.

Innervation of the Cerebral Veins as Compared with the Cerebral Arteries: A Histochemical and Electron Microscopic Study

The distribution of nerve fibers in the cerebral veins was studied by catecholamine fluorescence simultaneously with acetylcholinesterase (AChE) histochemistry. A comparison of nerve fibers in the cerebral arteries was made, The ultrastructure of terminal boutons in the veins fixed with potassium permanganate was also studied, In the adventitia of the cerebral artery, green fluorescent aminergic fibers and brownish AChE-reactive (probably cholinergic) fibers were observed. In contrast, the cerebral venous system showed no AChE-positive fibers. Catecholamine fluorescent varicose fibers were detected in the dural sinus, the internal cerebral vein, and the superficial vein of Labbé. The highest density of aminergic fibers was found in the dural sinus and the second highest in the internal cerebral vein. Most of the terminal boutons in the adventitia of the cerebral veins were found adjacent to a muscle-like cell and showed only cored vesicles under electron microscopy. Results of our study suggest that the cerebral venous system has a neurogenic innervation, mainly from aminergic fibers, which is different from the neurogenic supply to the cerebral arterial system.

The distribution of adrenergic receptors in cerebral blood vessels: an autoradiographic study

The first morphological evidence of the existence of adrenergic receptors (alpha 1, alpha 2 and beta) within the vascular walls of the central nervous system were presented using the in vitro receptor autoradiographic technique. In the rat pial arteries all three types of adrenergic receptors were demonstrated, whereas the human pial arteries failed to show significant autoradiographic grains of alpha 1 type of adrenergic receptors indicating a considerable inter-species difference in the distribution of adrenergic receptors. alpha 2 and beta receptors in human pial arteries were found not only in the arterial smooth muscle layers but also in the endothelial layers. This suggests a possibility that circulating sympathomimetic agents play some role in controlling the tone or permeability of vascular walls within the central nervous system. A distinct distribution of alpha 1 receptors in cortical layer IV where the vascular plexus was richest may suggest a relation of alpha 1 receptors and blood flow of brain parenchyma.

Immunohistochemical Demonstration of Vasopressin Nerve Fibers in the Cerebral Artery

Vasopressin-immunoreactive nerve fibers were demonstrated in the cerebral pial arteries by peroxidase immunohistochemistry. In the large pial artery (proximal part of the middle cerebral artery), they ran longitudinally to the long axis of the vessel. They ran in a spiral pattern in the distal part of the middle cerebral artery. Even in small arteries, vasopressin nerve fibers were found arranged in a longitudinal fashion. The present morphological data suggest that vasopressin nerve fibers in the cerebral artery may play a role in cerebral circulation.

Localization of monoamine oxidase (MAO) in the rat peripheral nervous system — Existence of MAO-containing unmyelinated Axons

Using a new coupled peroxidation method modified by adding nickel ammonium sulfate, we demonstrated the localization of monoamine oxidase (MAO) in the rat peripheral nervous system. MAO was localized in the endothelial cells of endoneurial vessels, in Schwann cell cytoplasm encircling myelinated axons, and in some unmyelinated axons. The morphometric ratio of these MAO-containing axons to the total unmyelinated axons was 10-13%. These MAO-containing unmyelinated axons were assumed to coincide with postganglionic sympathetic noradrenergic ones passing in the sciatic nerve. Histochemical MAO staining may be utilized to identify the postganglionic sympathetic nerves in normal and pathological conditions at the electron microscopic level in particular.

Autotransplantation of peripheral cholinergic neurons into the brains of Alzheimer model rats

SummaryCurrent hypotheses regarding Alzheimers disease implicate cholinergic function. In this study, peripheral cholinergic neurons in the vagal nodosal ganglion were transplanted into the brains of Alzheimer model rats. Eighteen Sprague-Dalwey strain rats were divided into three groups: 1) unoperated control rats, 2) rats that had undergone bilateral destruction of the nucleus basalis of Meynert (NBM) (Alzheimer model), and 3) the transplantation group in which the vagal nodosal ganglion was transplanted into the cerebral neocortex one week after the bilateral destruction of the Meynert nucleus. Seven weeks after the transplantation rat behaviour was assessed using psychological tests (spontaneous activitiy, passive avoidance response and the Hebb-Williams maze test). The Alzheimer model rats had a statistically significant increase in spontaneous activity in comparison with controls (P<0.01). The transplant rats showed some amelioration of this abnormal increase in spontaneous activity observed in the Alzheimer model rats. All of the control rats showed conditioned passive avoidance responses, while only one Alzheimer model rat retained is shocked-conditions behaviour before 24 hours (P<0.01). Three of the six transplanted rats showed complete improvement in the passive avoidance response test. In the Hebb-Williams maze test, the rats with NMB lesions made more errors than the control rats. The transplanted rats had a lower number of errors than NBM-lesioned rats but still more than the controls. Histological examination revealed many cholinergic cells in the transplanted tissue, especially in the area adjacent to the cerebral cortical surface.The present results indicate that autotransplantation of peripheral cholinergic cells ameliorates abnormal behaviour in Alzheimer model rats.

Transcortical sensory aphasia following the unilateral left thalamic infarction— A case report

Abstract We reported a 60-year old right handed woman who had transcortical sensory aphasia caused by left thalamic cerebral infarction. She had a mild right hemiparesis involving the face, with hyperactive tendon reflexes. Tactile and pain sensations were decreased in the right side involving the face without visual field defect. Spontaneous speech was remarkably reduced, and she had a remarkable disturbance in object naming. Her auditory comprehension and writing were severely disturbed. This contrasted with full preservation of repetition of words and short sentences (5

Peptidergic innervation of cerebral blood vessels

6 words). A CT scan 3 days later showed an infarct in the left ventral region of the thalamus. In the CBF (cerebral blood flow) study, 123I-IMP SPECT (single photon emission CT) showed a low flow in the left temporal and occipital lobes. We concluded that there might be thalamic aphasia caused by an occlusion of the left posterior communicating artery directly affecting the area served by left posterior cerebral artery.

Distribution of GABA‐T‐intensive neurons in the rat hindbrain

Morphological and ohysiological studies concerning the innervation of peptidergic nerve fibers were carried out using inmtmohistochemistry with the PAP and hydrogen clearance method, respectively. Vasoactive intestinal polypeptide (VIP) and substance P (SP) immunoreactive nerve fibers were distributed within the adventitial layer of Dial arteries in the central nervous system, including the spinal cord. In cerebral pial arteries nmny VlP ~reactive fibers ran mainly in a spiral pattern almost identical to that of aoetylcholinesterase-positive fibers, suggestive of the coexistence of VlP and acetylcholine in the Dial arteries, as was reoorted in the autonomic ganglia and the cerebral cortex (H6kfelt and Lundberg 1983, Eckenstelnand Baughmsn 1984). Ultrastructural study of ~stainedmaterial demonstrated that most VIP immunostained fibers and cells were also ntmmrous in the cerebral cortex. Some of thamwere found very close to the intraparenchymal blood vessels, indicating a strong functional correlation between VIP fibers mud arterial smooth muscles. In contrast, SP ~opositive fibers around pial arteries ran in a meshwork pattern and lay relatively apart from the arterial smooth muscle layer. Neither a nerve fiber nor a cell soma immunostainedwith SP was observed within the cerebral cortex. A physiological study to investigate the regional cerebral blood flow (r-CBF) using hydrogen clearance methoddemonstrated that iontophoretically injected VIP increased the r-CBF of the rat cerebral cortex, but SP failed to show significant change in r-CBF. These results suggest an important role of VIP neurons in regulating the cerebral blood flow.