2000 Fiscal Year Final Research Report Summary
IONIC MECHANISMS OF FUNCTIONAL MATURATION OF THE BUCCAL STRETCH RECEPTOR
| Project/Area Number |
10671751
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Functional basic dentistry
|
|---|
| Research Institution | TOKYO DENTAL COLLEGE |
|---|
Principal Investigator |
YAMAMOTO Tetsu TOKYO DENTAL COLLEGE, DEPARTMENT OF DENTISTRY, LECTURER, 歯学部, 講師 (90096511)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
HIRAYAMA Akihiko TOKYO DENTAL COLLEGE, DEPARTMENT OF DENTISTRY, ASSISTANT, 歯学部, 助手 (30130131)
|
|---|
| Project Period (FY) |
1998 – 2000
|
| Keywords | MASTICATORY MUSCLE / MUSCLE RECEPTORS / DEVELOPMENT / POTASSIUM CHANNELS / HYALURONAN |
|---|
| Research Abstract |
The buccal stretch receptor (BSR) is a mechanoreceptor that is located on the surface of the jaw closing muscles of rodents. In rats, the threshold stretch amplitude of the BSR to exhibit sustained discharges falls from 10 days to 3 weeks after birth and its static sensitivity increases between 2 and 4 weeks after birth. This investigation examined contribution of potassium channels in the sensory nerve endings of the BSR to its functional maturation. Immunoreactivity with the antibody to hyaluronate was recognized in the capsular space of the BSRs after 2 weeks of age. When hyaluronidase was applied to the BSR whose outer capsule was resected, the static response of the BSR was disappeared. These findings suggest that hyaluronate in the capsular space regulates the maturation of static sensitivity of the BSRs by ionic mechanisms. When effects of potassium channel blockers on their discharges were analyzed, tetraethylammonium (TEA, 0.1-1 mM) depressed the frequency of discharge of all BSR units tested over the response range. At higher concentrations (1-10 mM), TEA made the response of BSRs phasic. 4-aminopyridine (0.1-1 mM) induced spontaneous discharge in all units tested and depressed the static sensitivity in dose-dependent manner. These findings suggest that the delayed rectifier current at the encoding site of nerve endings of the BSR induces the static response of this receptor, and that the A-type current at a similar site may influence its static sensitivity. Immunohistochemistry on BSRs isolated from 1 week old rats revealed positive labeling with an antibody against Kv1.4 subunit of A-type potassium channel in preterminal unmyelinated axons. After 3 weeks of age, Kv1.4 was detected only in internodal segments of the axons, suggesting A-type potassium channels in preterminal axons were covered by formation of myelin sheaths.
|
