S~9

9 Limbic system

Thalamic project ions to the hippocampal formation and entorhinal area in the cat

MAMORU YANAGIHARA ~, KATSUHIKO ONO ~, and KAHEE NIIMI, Third Department of Anatomy, Okayama University Medical School, Shlkata-cho 2, Okayama 700, Japan

The thalamic project ions to the hippocampus and entorhinal cortex in the cat have been studied by the retrograde and anterograde axonsl transport techniques. Under sodium pentobarbital anesthesia (40 mg/kg, l.p.), injections of HRP or WGA-HRP were made stereotaxically by the mlcrosyringe of Hamilton under pressure. After two days, the animals were sacrified under deep barbital anesthesia, and then the brains were sectioned at 50 ~m thickness on a freezing microtome. Injections o 4 HRP into the hippocampus and dentate gyrus led to retrograde labeling of cells in the reuniens nucleus of the ipsilateral thalamus throughout its anteroposterior extent. The labeled cells were found largely in the parvocellular ventral part, but a few labeled cells were encountered in the dorsal part at anterior levels. Following an injection of WGA-HRP into the paraaubiculum area, a large number of labeled cells were seen in the medial portion of the ventral part of the reuniens nucleus and in the rhomboid, central medial, anteromedial, anterodorsal and lateral dorsal nuclei. Many labeled cells were also found in the anteroventral nucleus and the medial part of the medial pulvinal nucleus. Injections into the ventromedial division of the latral entorhinal area led to abundant labeling of cells in the anterior paraventricular nucleus and the lateral portion of the ventral part of the reuniens s After an injection into the ventral division of the lateral entorhinal area, s large b ~f labeled cells were seen in the central portion of the reuniens nucleus, and a lesser number in the paraventricular nucleus. Injection of HRP into the dorsal division of the lateral entorhinal area and area 35 led to a large number of labeled cells in the reunienm and central medial nuclei, and less numerous labeled cells in the dorsolateral part of the lateral dorsal nucleus. When an injection of WGA-HRP was made more caudally into the medial entorhinal area, abundant labeled cells were seen in the dorsal part of the reuniens nucleus and in the anteromedial, snteroventral and lateral dorsal nuclei. In our anterograde experiments, injections of WGA-HRP into the reuniens nucleus resulted in terminal labeling in the superficial layers of the subicular area and the neighboring part of the hippocampus and of the entorhinal area.

SOME PROPERTIES OF THE HIPPOCAMPAL MINISPINDLE WAVE

NORI0 KANAMORI, Department 0s 0ral PhysloloEy, School of Dentistry,

Tokushima University, Kuramoto-cho, Tokushima, 770 Japan

Under Nembutal anesthesia, eat dorsal hippocsmpl were chronically impaled

with stainless steel wires (32 ~m diameter, ca.500 k~ ). The tips of the

electrodes were aimed to scatter in a functional lamella parallel to the

saEital plane. Electrlcal activity was recorded extracellularly in the free-

movlnE condition and the mlnlspindle waves simultaneously recorded from

d i f f e ren t po i n t s were compared. I n add i t i on t o the p rev i ous l y r epo r t ed good

concurrency, some pairs of minlsplndle waves recorded from different points

showed very good similarities so that the prclse time difference can be

measured. On the assumption that the trigger slgnal/mlnlspindle wave itself

travels along the lamalla, the conduction velocity was calculated: 0.6 • O.3

m/see. Occasional dwarflnE 0s a component wave in a mate spindle to the other

suEKests the existence of both positive and negative components. Besides the

symmetrical type o f spindle wave, comb shaped types, both positive and

negative, wares observed. While mlnisplndle waves of higher frequency ( more

than 85 Hz, minispindle I ) occurred dominantly in the CA1 region, another

type ( 40 - 85 Hz, mlnlsplndle II ) of spindle wave appeared when the elctrode

t i p l o ca ted i n the r eg i o i n f e r l o r / sub l cu l um and became dominan t i n the h i l u s .

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COMPARISON OF CINOULAR FIBER CONNECTIONS IN THE CAT AND MONKEY

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cases and reciprocal in some cases) were'observed in the clngular area of Rose and Woolsey, as al- ready reported (Neurosei. Lett., Suppl. 17, $38). In the monkey, the WGA-HRP injections in the posterior part of the anterior eingulate gyrus and the anterior part of the posterior c~ngulate gyrus produced common transports (retrograde in all cases and reciprocal in most cases) to the premotor, posterior parietal and precuneal areas, the principal, olfactory, rhinal and superior

For one injection that located in the most anterior part of the anterior eingulate gyrus, con- nections with the posterior parietal, preouneal and premotor areas could not be demonstrated. The projection pattern of the middle part of the eingulate gyrus, i. e. extensive connections with

suprasylvian gyrus, the insula with the anterior sylvian gyl'us and the area of the olfactory sul- cus with the ventrolateral orbital cortex, respectively, in the cat. From these findings and

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agranular cortex in the monkey located in the most anterior part of the cingulate gyrus (anterior to A 23-25 in Macaca fuscata), Fiber connections of this area resemble the cat anterior limbic area of Rose and Woolsey; for example, a lack of connection with area 7. The anterior limbic area is thought to be area 2h and the cingular area, area 23. The borderline of these areas is between the agranular and dysgranular cortices. If the monkey eingulate cortex is divided with cept it would locate about 10 mm anterior to the prevailing extension line of the central sulcus.

AN AUTOPSY CASE SHOWING MARKED HIPPOCAMPAL ATROPHY OF PERINATAL ORIGIN WI~IOUT GROSS MEMORY DISTURBANCE

JUNICHI SATOH, TOSHIO MIZUTANI and YOSHIO MORIMATSU Department of Clinical Neuropathology, Tokyo Metropolitan Institute for Neurosciences, 2-6 Musashidai, Fuchu, Tokyo 183, Japan

Case: 22 year old male, who was diagnosed as havino athetotic cerebral palsy due to ~n-~icterus, and had been bedridden all his life. ~e could not speak because of severe athetosis, but he could notify his intention with changes of expression or muscular tonus. He showed relatively good understanding and no gross disturbance of either short or long term memory. Neuropathology: Besides marked atrophy of the globus, pallidus and the suhthalamus', bs marked atrophy of the hippocampus was noticed. Histologically marked neuronal loss, glial proliferation and fibrilla- ry gllosls were observed at the cornu ammonis and dentate gyrus. The subiculum showed mild neuronal loss but the parahippocampal gyrus was intact. The other cerebral cortex (including cingulate, T3-4 etc), thalamus (A,DM etc), mammillary body and amygdala were "all intact. Discussion: The function of human hippocampus in relation to memory had been s t u d i e d ~ t h cases of temporal lobectomy for epilepsy or limblc encephalitis, and knowledge from cases of early onset or with localized lesion only in the hippocampus had been limited. The authors consider this case to pose two tentltive theories: one is that tile hlppocampus (esp. cornu ammonis and dentate gyrus) does not play an important role in the function of memory; and the other is that hippocampal lesion of early onset is compensated for by another part of the brain.

I t has been suggested that septohippocampal projections are important for hippocampal theta ac- t i v i t y , and that theta generation is localized in the stratum oriens of the hippocampus and the mo- lecular layer of the fascia dentata. In our previous study in rats, the laminar f ie ld potential analysis showed that hippocampa) negative responses to the medial septal nucleus stimulation were localized only in the alve,s and the stratum oriens. The retrograde HRP-labeling method revealed that cell bodies in the medial septum-diagonal band complex were retrogradely labeled with HRP in- jected into the stratum oriens but not with HRP injected into other strata or layers of the hippo- campus or the fascia dentata. From these findings, we considered that the medial septal nucleus sends excitatory inputs mainly to the basal dendrites of hippocampal pyramidal cel ls, and that posi- ~ ~ s ~ X ~ ~ ? r d ~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

c i the present study, we further examined septohippocampal projections in rats with the anterograde HRP-labeling method, to provide a detailed distr ibut ion pattern of septal f iber terminals to the hippocampal formation. A single injection of 0.08 ~l of 50% HRP was stereotaxical- ly given into the medial septum-diagonal band complex with a Hamilton syringe under pentobarbital anesthesia. After survival for 48 h, the animals were deeply reanesthetized and perfused int ra- cardial ly with 7~ formalin. The brains were removed immediately and serial sagittal frozen sections were made at a thickness of go pm. A large number of axons labeled anterogradely with HRP could be traced from the inJectio~ site in the medial septum-diagonal band complexto the hippocampal forma- tion. The labeled axons passed through the dorsal fornix, the fimbria and the alveus, and ended in the stratum oriens of f ields CAI to CA3 and in the hilus of the fascia dentata. The terminated ax- ons and boutons were very small in size and some axons had "en passant" bouton~. A number of label- ed axons were found in the stratum radiatum of f ie ld CA3. However, these axons almost passed through, entered the hilus, and ended as terminal boutons. In the molecular layer of the fascia dentata, very few axons labeled anterogradely were infrequently seen. In referring to data on ace- tylcholine receptors, the distr ibut ion pattern of anterogradely labeled axons i n t h i s study seemed to be in a good accordance with that of the nicot inic receptor sites in the hippocampa| formation.

ALTERATION OF LOCAL CEREBRAL GLUCOSE UTILIZATION FOLLOWING LATERAL HABENULAR LESIONS IN THE RAT

MASANORI ITO. M.D. * Department of Neurosurgery, Juntendo University School of Medicine, Bunkyo-ku, Hongo, Tokyo, l l 3 , Japan

In a number of pharmacological and physiological studies employing the 2-[14C]deoxyglucose method, rates of glucose u t i l i za t ion in the lateral habenula nucleus have been found to be altered. The deoxyglucose method was employed to map the distr ibut ion of the changes in local cerebral glucose u t i l i za t ion following unilateral and bi lateral e lect ro ly t ic lesions of the lateral habenula nucleus. Local cerebral gulcose u t i l i za t ion was measured one week after the placement of the lesions. Unilateral lesions of the nucleus had no effect on the rates of glucose u t i l i za t ion in the 79 brain structures examined. Bilateral lesions, however, produced selective reductions in glucose u t i l i za t ion in several structures compared to the result in sham-operated animals. Reductions were found in the dorsal and median raphe nuclei and the ventral and dorsal tegmental nuclei which receive projecting fibers mainly from the medial part of the lateral habenula nucleus. The rates of glucose metabolism in the interpeduncular nucleus andmammillary body were also reduced by the bi lateral habenular lesions. No anatomical structures rostral to the lesions were metabolically affected. Changes in metabolic ac t iv i t ies in the brainstem serotonergic raphe nuclei and tegmental nuclei suggest a functional role of these nuclei in the relay and integration of input from forebrain doperminergic limbic structures to the brainstem limbic and serotonergic raphe system via the lateral habenu]a.