ACTIVITIES OF ACETYLCHOLINE-METABOLIZING ENZYMES IN THE MASTICATORY MOTONEURONS OF THE RAT

1997 Fiscal Year Final Research Report Summary

• Project/Area Number: 07838032
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 咀嚼
• Research Institution: KYUSHU DENTAL COLLEGE
• Principal Investigator: KAWAGISHI Shigenori KYUSYU DENTAL COLLEGE,DEPARTMENT : DENTISTRY TITLE OF POSITION : ASSOCIATE PROFESSOR, 歯学部, 助教授 (20137334)
• Project Period (FY): 1995 – 1997
• Keywords: CHOLINE ACETYLTRANSFERASE / ACETYLCHOLINESTERASE / JAW-OPENING / JAW-CLOSING / MOTONEURON / RAT

Research Abstract

Masticatory alpha motoneurons in the rat were examined quantitatively for their activity of the acetylcholine-degrading enzyme, acetylcholinesterase (AChE). After the anterior digastric (jaw-opening) and masseter (law-closing) motoneurons were retrogradely labeled by the fluorescent tracers nuclear yellow and bisbenzimide respectively, the rats were administered with the ir-reversible AChE inhibitor diisopropyl fluorophosphate (DFP) and then allowed to survive for 3 hr for the synthesis of new enzymes. Serial frozen 20 mum sections of the brainstems were prepared and processed for AChE histochemistry using acetylthiocholine iodide as the substrate. The AChE activity of motoneurons labeled by the fluorescence was determined by measuring the absorbance at 470 nm in the cytoplasm using a microspectrophotometer. In the suckling and young adult animals, the anterior digastric motoneurons showed significantly higher AChE activity than the masseter motoneurons (p<0.001), but in the old rats such differences were not detected. In the young adult rats, there was no relationship between the AChE activities and soma areas of alpha motoneurons which were measured using an image analyzer. The activity of transmitter-synthesizing enzyme, choline acetyltransferase (ChAT), in the young rats was also examined. Thirty mum sections of the brainstems were prepared from the DFP-untreated rats and processed for ChAT immunohistochemisry using the peroxidase -antiperoxidase complex. The ChAT activity of motoneurons was measured as the absorbance at 450 nm of the peroxidase-reaction-products ; the ChAT activity was also significantly higher in the anterior digastric than in the masseter motoneurons (p<0.001).