Topographical Projections of cingulate cortex to the central lateral nucleus (CL) of thalamus in the cat was observed by means of retrograte HRP technique. After injection of HRP into rostral part of the CL, labeled cells were mainly distributed in ipsilateral anterior cingulate cortex. A few cells were also labeled in the corresponding location of the contralateral cingulate cortex. Following injections of HRP into caudal part of CL, the HRP-positive neurons were found in both anterior and posterior parts of the cingulate cortex ipsilaterally, the labeled cells were considerable sparser than in rostral injection cases. Labeled cell in all cases were located in inferior part of lamina Ⅴ and lamina Ⅵ. They are small to middle sized pyramidal neurons. These results suggest that the cingulate- CL projection are topographically organized.

Ascending and descending efferent projections of superior coUiculus were indentified by means of the anterograde horseradish peroxidase technique in the cat.Following injections of HRP into the rostral superior colliculus, a large number of labeled terminals were found mainly in several of the ipsilateral thalamic nuclei:ventromedial division of the ventral nucleus of the lateral geniculate body, zona incerta,lateral posterior nucleus, parafasciculus nucleus and centromedian nucleus. The mediodorsal nucleus and thalamic reticular nucleus were also found mildly labeled.Labeling were most heavily concentrated in the ipsilateral dorsolateral division of pontine nucleus and caudal region of parabigeminal nucleus. The dorsal part of medial accessory olivary was the only nucleus labeled contralaterally. After injecting HRP into the caudal superior colliculus, only the dorsolateral division of pontine nucleus was densely labeled, while labeled terminals of caudal parabigeminal nucleus signifcantly reduced in amount. No labeled terminals were found in the thalamus as well as medial accessory olivary nucleus. These results indicate that the efferent connections of superior colliculus are topographically organized.

The afferent connections and topographical organization of the central lateral nucleus were studied with HRP retrograde tracing technique in 10 adult cats. The central lateral nucleus received projections from the forebrain, brainstem and cerebellum. The nuclei, projected to the caudal region of the central lateral nucleus, included the dorsal division of the ventral lateral geniculate nucleus, the thalamic reticular nucleus and the deep layers of superior colliculus, primarily on the ipsilateral side. The intralaminar thalamic nucleus, the lateral hypothalamus and the reticular part of substantia nigra sent axons to terminate in the rostral region of the central lateral nucleus, with an ipsilateral predominance. The nuclei, projected to the whole length of the central lateral nucleus, were the vestibular neuclei, the reticular formation of brainstem, zona incerta, pretectal area, cells surrounding the occulomotor complex, principal sensory trigeminal, cuneatus, gracilis as well as cerebellar dentate. The vestibular nuclei and the reticular formation of brainstem were found bilateral projection, the former predominantly in contralateral, the latter mainly in ipsilateral part. Except the zona incerta, pretectal area and cells surrounding the occulomotor, the rest were labeled primarily on the contralateral side. If HRP was injected into the central lateral nucleus and spread to the ventral anterior nucleus of thalamus, a lot of HRP-positive cells were found in the entopeduncular nucleus, while the ventral tegmental nucleus of Gudden was filled with densely labeled terminals mainly on the ipsilateral side. These findings indicate that the central lateral nucleus of thalamus may be involved multiple sensory and motor functions.

The topographical projection between the parabigeminal nucleus and the superiorcolliculus in the cat was investigated by retrograde and anterograde HRP tracingtechnique.Following HRP injection in the rostral superior colliculus,the labeledsomata were found predominantly in the rostral region of contralateral parabigeminalnucleus,but labeled terminals were heavily distributed in the ipsilateral parabigeminalnucleus,mainly in the caudal region.Following injection of HRP into caudal superiorcolliculus,the labeled somata and terminals were seen in ipsilateral parabigeminalnucleus,chiefly in caudal part,but their number was significantly decreased.It wasnoted that the labeled somata were sparse but labeled terminals were not found inthe parabigeminal nucleus,when the injection was restricted to superficial layers ofsuperior colliculus.After HRP injection into deeper layers of superior colliculus,there existed not only the labeled somata but also the labeled terminals in theparabigeminal nucleus,the former was distributed in bilateral parabigeminal nucleus,the latter in ipsilateral nucleus,chiefly in the caudal part.These results show thatthere are topographical connections between the parabigeminal nucleus and superiorcolliculus,and the parental somata contributing axons to the parabigeminal nucleusare located in deeper layers of the ipsilateral superior colliculus.

The afferant projections and their chemical nature from the midbrain raphe nuclei and periaqueductal gray to the thalamic ventral posterior nucleus were st- udied by HRP retrograde tracing combined with PAP immunocytochemical method Following injections of HRP into the thalamic ventral posterior nucleus, and reactions by HRP and PAP were performed subsequently. The double labelling cells containing HRP-positive granules and substance P-like immunoreactivity were found in various areas of brain, that is, the contralateral principal sensory nucleus of trigeminal nerve,nucleus gracilis,nucleus cuneatus, bilateral ventrola- teral divisions of the periaqueductal gray and midbrain raphe nuclei.A comparison of cell counts of double labeled cells with the total HRP-labeled cells indicated that the cells observed in the dorsal raphe nuclei were 21?7 in each rat, which constituted 48% of total HRP-labeling cells; The double labeling neurons in nuclei raphe centralis superior were found in two cases only, the cell bodies were very sparse and distributed mainly in the caudal area of these nuclei The double labeling cells were detected in bilateral ventrolateral divisions of periaqu- eductal gray, predominantly ipsilaterally. The double labeling cells observed in each rat were 26?9 ipsilaterally and 11?4 contralateraIly. The numbers of double labeling cells were 38% of the total counts of HRP-labeling cells in each side. These results above indicate that the thalamic ventral posterior nucleus receives afferent projections from midbrain raphe nuclei and ventrolateral division of periaqueductal gray and in the pathway, a part of substance P-positive neurons are exhibited. Therefore, this study provides evidence for existance ascending projection of substance P-like immunoreactivity.

The distribution of virus antigen of epidemic hemorrhagic fever (EHF) in infected suckling mice brain was studied by indirect immunofluorescence procedure. The specific fluorescence was presented in the following areas: (l)the limbic system, including the cingulate cortex, the piriform cortex, the anterior olfactory nucleus, the lateral septal nucleus, the hippocampus, the dental gyrus, the dorsomedial nucleus and lateral nuclei of thalamus, and several nuclei of the hypothalamus; (2)the special sensory nuclei, such as the medial and spinal vestibular nuclei, the cochlear nucleus, and the lateral lemniscus nucleus; (3)the nuclei associated with analgesic function, including the periaqueductal gray substance, the trigeminal sensory nucleus, the raphe nuclei of midbrain etc; (4)the extrapyramidal structures, for example, the caudal-putamen, the pallidum, the entopeduncular nucleus, the cerebellum and several nuclei of reticular formation in brainstem.

The different distributions of substance P(SP)-and leucine-enkephalin (L-ENK)-like immunoreactive neurons in the midbrain raphe nuclei of the rats have been studied, using PAP immunocytochemical technique. The results showed four main points: 1. SP-containing immunoreactive cell bodies were only seen in the most caudal part of the dorsal raphe nucleus, the average number of SP-positive cell bodies was about 167 in each animal. The L-ENK-like immunoreactive positive cell bodies were found almost in the whole length of the dorsal raphe nucleus, the L-ENK-positive cell bodies were about 132 in each animal. 2. L-ENK-Iike immunoreactive perikarya were mainly located in the midline area of the dorsal raphe nucleus. Besides the above areas, SP-containing immunoreactive cell bodies were also located bilaterally in the extended area from the raphe. 3. L-ENK-containing immunoreactive cell bodies constantly appeared in the median raphe nuclei, the average number was about 199 in each animal, but SP-containing immunoreactive bodies were only observed in this nucleus of two rats. 4. Some SP-like immunoreactive cell bodies or processes were observed in the vincinty of vascular walls, but the L-ENK positive neurons were not found similar results. The present experiment showed that the SP-like immunoreactive perikarya is located in the median raphe nuclei of the rat.

The present investigation was performed on six adult cats. The morphology and distribution of the labeled cells in the ventral lateral geniculate nucleus (LGNv) were observed. Following the injection of horseradish peroxidase (HRP) into the deeper layers of the superior colliculus the labeled cells were found to concentrate ipsilaterally in the ventral part of the rostromedial division of the LGNv. The HRP-positive cells were composed of large-sized, smaller, round and oval ceils. In the cases of injection of HRP into the rostral pretectum, the HRP-positive cells were seen bilaterally in the caudolateral division of LGNv mainly in the contralateral part, while the labeled cells were found ipsilaterally in the ventral part of caudolateral division after injection of HRP into the caudal pretectum. These cells were smaller than that large ones of superior colliculus injection. The results indicate that the projection of the LGNv to the superior colliculus and pretectum is organized topographically.