Craniofacial and TMJ Effects after Glutamate and TRH Microsphere Implantation in Proximity to Trigeminal Motoneurons of Growing Rats

• Published in: Journal of dental research Vol. 76; no. 8; pp. 1437 - 1452
• Main Authors: Byrd, K.E., Sukay, M.J., Dieterle, M.W., Yang, L., Marting, T.C., Teomim, D., Domb, A.J.
• Format: Journal Article
• Language: English
• Published: Los Angeles, CA SAGE Publications 01.08.1997; SAGE PUBLICATIONS, INC
• Subjects: Analysis of Variance; Animals; Cell Count; Dentistry; Drug Implants; Glutamic Acid - administration & dosage; Glutamic Acid - pharmacology; Male; Mandibular Condyle - drug effects; Mandibular Condyle - growth & development; Masticatory Muscles - drug effects; Masticatory Muscles - growth & development; Masticatory Muscles - innervation; Maxillofacial Development - drug effects; Microspheres; Motor Neurons - drug effects; Muscle Development; Rats; Rats, Sprague-Dawley; Stereotaxic Techniques; Temporomandibular Joint Disc - drug effects; Temporomandibular Joint Disc - growth & development; Thyrotropin-Releasing Hormone - administration & dosage; Thyrotropin-Releasing Hormone - pharmacology; Trigeminal Nuclei - drug effects; motoneuron; TRH; trigeminal; microspheres; glutamate
• ISSN: 0022-0345; 1544-0591
• DOI: 10.1177/00220345970760080601

The sequelae of sustained, in vivo delivery of two important neurotransmitter substances, glutamate and thyrotropin-releasing hormone (TRH), upon craniofacial growth and development have previously not been investigated. Our purpose was to document and compare the relative effects of glutamate and TRH microspheres stereotactically placed in proximity to trigeminal motoneurons within the trigeminal motor nucleus. The following null hypotheses were tested: (1) TRH microspheres in proximity to trigeminal motoneurons have no significant effect upon the craniofacial skeleton, and (2) there are no significant differences between the relative effects of chronic, long-term delivery of glutamate and TRH upon the neuromusculoskeletal system of growing rats. Forty male Sprague-Dawley rats were divided into 4 experimental groups (glutamate microspheres, TRH microspheres, blank microspheres, sham surgeries) and underwent stereotactic neurosurgery at 35 days; 5 rats of each group were killed at 14 and 21 days for data collection. Histology revealed that implants were clustered in the pontine reticular formation, close to the ventrolateral tegmental nucleus. Both glutamate and TRH rats had implant-side deviation of their facial skeleton and snout regions; 4 x 2 ANOVA and post hoc t-tests revealed significant (P ≤ 0.05, 0.01) differences between groups and sides for motoneuron count, muscle weight, and osteometric data. TRH rats also demonstrated larger implant-side TMJ discs and mandibular fossae in comparison with the other groups. The stated null hypotheses were therefore rejected.