EXPERIMENTAL STUDIES OF NEUROANATOMICAL BACKGROUND OF FEEDING PATTERNS SHIFTING FROM SUCKING TO BITING

• Project/Area Number: 59480355
• Research Category: Grant-in-Aid for General Scientific Research (B)
• Allocation Type: Single-year Grants
• Research Field: Morphological basic dentistry
• Research Institution: TOKYO MEDICAL AND DENTAL UNIVERSITY FACULTY OF DENTISTRY
• Principal Investigator: KUBOTA KINZIRO TOKYO MEDICAL AND DENTAL UNIVERSITY FACULTY OF DENTISTRY, 歯学部, 教授 (00013805)
• Co-Investigator(Kenkyū-buntansha): NAGAE KAZUKI TOKYO MEDICAL AND DENTAL UNIVERSITY FACULTY OF DENTISTRY, 歯学部, 助手 (20172497) ; SHIBANAI SHUNJI TOKYO MEDICAL AND DENTAL UNIVERSITY FACULTY OF DENTISTRY, 歯学部, 助教授 (90014018)
• Project Period (FY): 1984 – 1986
• Project Status: Completed (Fiscal Year 1986)
• Budget Amount: ¥6,100,000 (Direct Cost: ¥6,100,000); Fiscal Year 1986: ¥1,400,000 (Direct Cost: ¥1,400,000); Fiscal Year 1985: ¥2,000,000 (Direct Cost: ¥2,000,000); Fiscal Year 1984: ¥2,700,000 (Direct Cost: ¥2,700,000)
• Keywords: SUCKING / BITING / MASSETER MUSCLE / ORBICULARIS ORIS MUSCLE / MOTOR ENDPLATE / MYELINATION / FACIAL NERNE / MASSTERIC NERVE / HRP-LABELING / FACIAL MOTONEURON / TRIGEMINAL MOTONEURON / MUSCLE SPINDLE / ATROPHY

Research Abstract

The mammalian feeding pattern is shifting from sucking to biting after it has born. What is the neuroanatomical background of this feeding pattern? Concerning this problem, is there seen the developmental time difference in the neurons related to the sucking and biting movements and/or in the peripheral effectors relative to the both movements? The mechanism has remained unsolved. To define these questions, 1) the development of the masseter and orbicularis oris muscles, 2) the development of the trigeminal and facial motoneurons, and 3) the effect of the soft diet on the masseter muscle were studied on the mouse by electron microscopy and HRP-labeling technique.
The results obtained are as follows: 1) The motor endplate in the orbicularis oris muscle revealed the postsynaptic fold, prominent accumulation of the synaptic vesicles and the active zone in the 17-day-old embryo, while the motor endplate in the masseter muscle showed the delayed developmental feature, flat postsynaptic sarco plasmic membrane. 2) The intramuscular nerve fibers of the orbicularis oris muscle have begun to be myelinated in the 3-day-old young, while the myelination of the nerve fibers of the masseter muscle occurred delayed one day in the 4-day-old young. 3) The interior receptor organ (muscle spindle) in the masseter muscle revealed the principal structure in the 4-day-old young. 4) The facial motoneuron demonstrated a definite multipolar figure by HRP-labeling at birth, while the trigeminal motoneuron was obscure in figure. 5) The HRP-labeled figure of the both motoneurons appeared in the same degree in the 7 to 10 day-old young. 6) The area of the neuron soma was superior in the facial nucleus to that in the trigeminal nucleus at birth, while the increasing rate of the area of the neuron soma was superior in the trigeminal nucleus to that in the facial nucleus in the 7 to 14-day-old young. 7) The atrophy of the muscle spindles appeared in the masseter muscle of the mouse fed with the soft powder diet for one year following weaning. In conclusion, it will be emphasized that the growth of the neuromuscular mechanism is superior in the sucking system to that in the masticatory system at birth and that the neuromuscular mechanism developed at full speed during the period of the 7 to 14-day-old. But it is suggested that the neuromuscular mechanism of the masticatory system will be atrophized by feeding on the soft diet.

Research Products

• [Publications] OHKUBO,KENICHI: BULLETIN OF TOKYO MEDICAL AND DENTAL UNIVERSITY. 34(1). (1987)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] OHKUBO, KENICHI: "DEVELOPING MUSCLE SPINDLE IN THE MOUSE MASSETER MUSCLE STUDIED BY ELECTRON MICROSCOPY" BULLETIN OF TOKYO MEDICAL AND DENTAL UNIVERSITY. 34(1). (1987)
  • Description: 「研究成果報告書概要(欧文)」より