The origin of afferent connections to the hypothalamic paraventricular nucleus was studied in the rats with the method ot retrograde axonal transport of HRP.A small amount of HRP was delivered electrophretically into the hypothalamic paraventricular nucleus. The HRP labelled cells ware observed in the lateral septal nucleus, amygdaloid nucleus, hippocampus, subiculum,bed nucleus of the stria terminalis, -parafascicularic nucleus of the thalamus, anterior hypothalamic area, suprachiasmatica nucleus, supraoptic nucleus, circalaris nucleus, hypothalamic dorsomedial nucleus, hypothalamic ventromedial nucleus, posterior hypothalamic nucleus, arcuate nucleus, mamillaris nucleus, midbrain central gray, dorsal tegmental nucleus, lateral parabrac-hial nucleus, median raphe nucleus, locus coeruleus, solitary nucleus and lateral rati-cular nucleus

Seven adult albino rats were used for this study. The 50％ HRP solution was injected into the cervical enlargment unilaterally. Labelled neurons were mainly found in the nucleus paraventricularis, nucleus lateralis, nucleus paraventricularis, nucleus lateralis, nucleus perifornicalis, nucleus hypothalamicus anterior, nucleus hypothalamus posterior, nucleus suprachiasmaticus, nucleus supraopticus and nucleus periventricularis ipsilaterally. Most of the labelled neurons were found in nucleus paraventricularis hypothalamicus, less in the nucleus lateralis and only a few in other nuclei.The authors suggest that the efferent projections from the hypothalamus to the spinal cord in the rat may play a role in the integrative function of the spinal cord. which may be involved in the process of acupuncture analgesia.

Attempts were made to determine the cells of origin from the thalamus to the spinal cord by using the retrograde tracer technique with horseradish peroxidase (HRP). The solution of HRP was injected into the intumescentia cervicalis unilaterally in eight albino rats. The results indicated that the HRP-labeled cells were located in the parafascicular nucleus, subparafascicular nucleus and the ventromedial nucleus of the thalamus. The function of spinal projection from these neuclei were discussed.

The efferent projections to the spinal cord from the brain stem were studied with HRP. Fifty per cent solution of HRP was slowly injected into the intumescentia cervicalis at six points on its right side in 10 albino rats and the HRP-labelled cells were found in the following nuclei:1. Of the midbrain: the nucleus linearis, nucleus raphe dorsalis, substantia nigra, nucleus ruber, nucleus cuneiformis, nucleus colliculus superior, nucleus Edinger-Westphal, nucleus Darkschewitsch, nucleus interstitialis (Cajal), nucleus ventralis tegmenti and nucleus dorsalis tegmentalis;2. Of the ports: the nucleus raphe magnus, nucleus medianus raphe, nucleus trigemini principalis, nucleus lemnisci lateralis, nucleus reticularis pontis oralis, nucleus reticularis pontis caudalis, locus ceruleus, nucleus subceruleus, nucleus vestibularis lateralis, nucleus vestibularis medialis, nucleus parabrachialis and nucleus olivaris su- perior;3. Of the medulla oblongata: the nucleus raphe obscurus, nucleus raphe pallidus, nucleus gracilis, nucleus cuneatus, nucleus tractus spinalis nervi trigemini, nucleus tractus solitarius, nucleus commissuralis (Cajal), nucleus reticularis lateralis, nucleus reticularis paramedianus, nucleus reticularis gigantocellularis and nucleus olivaris inferior;4. Of the cerebellum: the nucleus medialis and lateralis.The functions of spinal projection from the nuclei raphe, reticularis, locus ceruleus, substantia nigra and the nucleus dorsalis tegmentalis have been discussed.

Cell bodies of the hypothalamus which project to various subdivisions of theparamedian midbrain were studied in the rat with the method of retrograde axonaltransport of HRP.After small amount of HRP was delivered electrophoreticallyinto the dorsolateral part of the central grey substance,the HRP-labelled cells werefound in the anterior hypothalamic nucleus,the ventromedial nucleus,the dorsome-dial nucleus,the dorsal premammillary nucleus,the ventral premammillary nucleus,the medial mammilary nucleus and the lateral mammillary nucleus,mainly in theipsilateral side.Following introduction of the enzyme into the ventral part ofcentral grey substance,there were HRP-labelled cells in the ipsilateral preoptic area,the lateral area of anterior hypothalamus(dorsal to the supraoptic nucleus),thelateral area of tuberal part,the ventromedial nucleus,the dorsomedial nucleus andthe dorsal premammillary nucleus.By introducing the HRP into the medial part oftegmentum,the HRP-labelled cells were observed in the preoptic area,the lateralarea of anterior hypothalamus,the ventromedial nucleus,the dorsomedial nucleus,the dorsal premammillary nucleus,the medial mammillary nucleus and the lateralmammillary nucleus.