The present experiments revealed that lingolabial repetitive pressurestimulation to the upper incisor evoked not only the tonic excitation but also the tonic inhibition of the masseter muscle in the rat. These reversed responses from the excitatory to the inhibitory reflex occurred depending on the background activity of the masseter muscle. When the background activity of the muscle was weak, the tonic excitatory reflex of the muscle was induced by pressure stimulation to the incisor. When the background activity of the muscle was strong, the tonic inhibitory reflex was elicited by the same pressure stimulation.
Reflex responses of the masseter muscle were also changed by the intensity of pressure stimulation. Weak pressure stimulation induced the excitatory reflex in the low background activity of the masseter muscle, but elicited the inhibitory reflex in the high background activity of the muscle. Strong pressure stimulation induced, even if in the low background activity of the masseter muscle, an inhibitory phase of the long duration before the excitatory phase, and extended the duration of the inhibitory phase in relation to the development of an incereasing background activity of the muscle.
Form above results, it is suggested that the excitatory and the inhibitory phases of the reflex were changed depending upon the state of the background activity of the masseter muscle and the stimulus intensity, and that overlapping of the excitatory and inhibitory phases caused many kinds of patterns of the periodontal jaw reflex.

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Transsynaptic neuronal destruction is known to follow the peripheral axotomy of primary neurons.The present study examines a hypothesis that the ectopic spike discharge of an injured primary neuron is the direct cause of strychnine-intensifiable transsynaptic destruction following peripheral nerve transection.In adult rats anesthetized with urethane, the effects of repetitive unilateral transection (7 times at an interval of 1 min) of the inferior alveolar nerve and/or systemic administration of strychnine (1 mg/ kg, i. p.) on morphology of neurons in the subnucleus caudalis of the nucleus of spinal trigeminal tract were evaluated. Approx.18 h after transection and/or strychnine administration, the rostralmost part of the subnucleus caudalis (ipsilateral to the transection if any) of the animals were histologically examined. Both transection and strychnine administration induced neuronal degeneration by themselves. At the light microscopic level, transection and strychnine administration revealed 7.2±4.4 and 3.3±5.6 degenerating neurons in a single transverse 1μm section of the subnucleus caudalis, respectively. When strychnine was administered 1 min prior to initiation of the repetitive transection, the number of degenerating neurons (17.0±2.9) was significantly greater than that revealed by transection or strychnine administration alone.Increased number of degenerating neurons were, by and large, in the dorsal half of the subnucleus.In contrast, strychnine administration 1 min after completion of repetitive transection revealed only 7.8±7.0 degenerating neurons, which is comparable with those revealed by transection alone. The latency and duration of the acute transsynaptic destructive effect of the nerve transection were, therefore, shorter than about 1 min at most. Injury discharge is the only known episode which follows neurotomy with such short latency and duration. The present results serve as a strong (if not conclusive) evidence for the hypothesis examined.

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We have reported (Mori et al. Neuroscience. Abstr. 15, 1985) that a new and complete somatic sensory area is found in the medial bank of the anterior suprasylvian sulcus (ASSS) of the cat cortex. Cells with receptive fields on the face form the rostral aspects of the medial bank of the ASSS. The caudal aspects of the ASSS are situated in the tail and hindlimb regions. We have designated this area as the Fifth Somatic Sensory Cortex (SV). In the present study, using the HRP method, we examined difference between the pattern of the cortical connections of the face region of large receptive fields in the first (SI) and in the fifth (SV) somatic sensory areas. The experiments were carried out on adult cats with a sedative dose of Ketamine (2mg/kg/hr). HRP was injected at the site where the SV neuron was activited by using natural somesthetic stimulation. When HRP was injected into the face region of the area 2 in SI labeled cells were located ipsilaterally in the area 3b, 1-2 of SI, the second somatic sensory cortex (SII), the fourth somatic sensory cortex (SW), SV and area 6aβ of the ipsilateral cortex, and the area 2 of SI of the contralateral cortex. On the other hand, when HRP was injected into the face of the SV region, labeled cells were located in area 4γ, areas 3b, 1-2 of the SI, SII, SIII and SIV and the area 2 of SI, SV of the contralateral cortex. The extent of these interconnections suggests that SV rec eives multiple sensory information and may function to integrate these inputs.

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We examined differences between the thalamo-cortical patterns of projection of the first (SI) and the fifth (SV) somatic sensory cortices, using HRP as a tracer.The experiments were carried out on adult cats with a sedative dose of Ketamine (2 mg/kg/hr). HRP was injected at the site where the S V neuron was activated by using natural somesthetic stimulation. When HRP was injected into the face region of SI, labeled cells were mainly located ipsilaterally in the ventral posterior medial nucleus (VPM). On the other hand, when HRP was injected into the face region of SV, labeled cells were located ipsilaterally in the ventral posterior medial nucleus (VPM) and the medial division of the posterior group (Porn). The large receptive fields of SV receive direct input from the VPM and Po, and this multiple afferent information suggests that SV have higher level integration than SI.

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Gingival pigmentation following the restorative procedure of a metallic crown was examined by the light and electron microscopy.
Numerous melanin pigment deposits were observed not only in cells of the basal layer and in the basement membrane but also in fibroblasts, macrophages and in the ground substance between collagen fibers in the proprial layer.The latter phenomenon was not evident in the non-pigmented control gingiva.
Massive brown colored material located in the deep part of proprial layer corresponded to the pigmented region.Sulfur and silver were detected in this material, using an electron probe X-ray microanalyser.
These findings suggest that the massive material was actually metallic fragments implanted into the gingival tissue during the prosthodontic procedures.
Numerous melanin pigment deposits surrounded the massive material suggesting an affinity of the melanin pigment for metallic elements such as silver.
It is considered that the implanted metal induced an abnormal movement of the melanin pigment down to the proprial layer, hence leading to the pigmentation of the gingiva.

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Jaw and oro-facial motor areas of cat cerebral cortex were defined by intracortical microstimulation (ICMS) and cortico-bulbar projection patterns and correlation between orbital (O) area and coronal (C) area were studied by injection of 5% wheat germ agglutinin (WGA) conjugated horse radish peroxidase (HRP) into these motor areas. Cytoarchitectonically, the C area was restricted to the area 3a, 6aβ and 4γ. Axons of cortical cells in this area descended through the ipsilateral pyramidal tract and terminal labelings of those axons projected to the contralateral side of magno-cellular division of spinal trigminal nucleus (5 SM), parbocellular division of spinal trigeminal nucleus (5 SP). On the other hand, the O area was restricted to area 43 and 6 aβ. Axons of cortical cells in O area descended through the ipsilateral pyramidal tract and terminal labelings of those projected to the ipsilateral side of juxta trigeminal region. C area and O area were reciprocally connected and projection from the C area to the O area was more dominant than that from C area to O area. These results suggest two separate direct descending pathways from the C and the O area to the brain stem, and suggest that the pathway is from the C area via the O area. Threfore, it is suggested that the O area might be a premotor area of the jaw and oro-facial regions and the C area is a primary motor area.

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In order to clarify some of the problems associated with the transport mechanisms of water and electrolyte especially in the basal and apical membranes of acinar portion of salivary gland, salivary flow rates and electrolyte concentrations of the rat submandibular glands were investigated by means of partial perfusions and intraductal injections of ouabain, ethacrynic acid and furosemide.
The Na⁺, K⁺-ATPase activities in the salivary glands were also examined biochemically and histochemically according to the methods of JøUrgensen, and of Guth and Albers respectively.
The following results were obtained.
1. Na⁺-K⁺ exchange pump of the basal membrane of acinar cell was inhibited by ouabain, ethacrynic acid and furosemide, respectively. Particularly, the inhibitory effect of ouabain was remarkable among these inhibitors.
2. It was assumed that there were inward sodium transport mechanisms exhibiting a specific sensitivity for ethacrynic acid and furosemide at the basal portion of the acinar cells.
3. The functional mechanisms of the Na⁺-K⁺ pump at the luminal membrane were significantly weak as compared with the Na⁺-K⁺ pump of basal portion.
4.It was suggested that ouabain inhibited Na⁺, K⁺-ATPase activity at the basal membrane of acinar cells, resulting in decrease of salivary flow rate.

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Bacterial lipopolysaccharide (LPS) was not mitogenic for murine T lymphocytes, but was capable of enhancing [³H] thymidine uptake of T lymphocytes stimulated by concanavalin A (Con A) in the presence of B lymphocytes or cmarophages (Mφ) in vitro. The mechanisms for the synergy of LPS and Con A on the proliferation of murine splenic lymphocytes and the relation of interleukin (IL)-production to the synergy were studied. The proliferative cells in the synergy were Lyt-1 positive T cells. A mixed cell population of T cells and B cells or Mφ produced active factor (s) after costimulation with Con A and LPS, and the factor (s) enhanced the proliferation of Con A-activated T cell population. The supernatants of spleen cell cultures which had been cultured with Con A and LPS contained greater amounts of IL 1 and IL 2 than those with LPS or Con A alone. Addition of exogenous IL 2, but not IL 1, into the Con A-activated T cell population increased their proliferative responses. These results indicate that LPS has the ability to enhance the production of IL 2 from Con A-activated T cells, and the IL 2 helps the proliferation of Con A-stimulated T cells. Thus, the experimental results strongly suggest that the synergistic effect of LPS and Con A on lymphocyte proliferation is mainly due to the action of IL 2.

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