Tooth movement activates the central amygdala and the lateral hypothalamus by the magnitude of the force applied.
OBJECTIVE
To determine if the magnitude of the force used to induce incisor tooth movement promotes distinct activation in cells in the central amygdala (CEA) and lateral hypothalamus (LH) of rats. Also, the effect of morphine on Fos immunoreactivity (Fos-IR) was investigated in these nuclei.


METHODS
Adult male rats were anesthetized and divided into six groups: only anesthetized (control), without orthodontic appliance (OA), OA but without force, OA activated with 30g or 70g, OA with 70g in animals pretreated with morphine (2 mg/kg, intraperitoneal). Three hours after the onset of the experiment the rats were reanesthetized and perfused with 4% paraformaldehyde. The brains were removed and fixed, and sections containing CEA and LH were processed for Fos protein immunohistochemistry.


RESULTS
The results show that in the control group, the intramuscular injection of a ketamine/ xylazine mixture did not induce Fos-IR cells in the CEA or in the LH. Again, the without force group showed a little Fos-IR. However, in the 70g group the Fos-IR was the biggest observed (P < .05, Tukey) in the CEA and LH compared with the other groups. In the 30g group, the Fos-IR did not differ from the control group, the without OA group, and the without force group. Furthermore, pretreatment with morphine in the 70g group reduced Fos-IR in these regions.


CONCLUSIONS
Tooth movement promotes Fos-IR in the CEA and LH according to the magnitude of the force applied.
Department of Morphology, Stomatology and Physiology, School of Dentistry of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
Ana Paula Ribeiro
AP
Novaes
Maria José Alves
MJ
da Rocha
Christie Ramos Andrade
CR
Leite-Panissi
D000679:Amygdala / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D000818:Animals; D001696:Biomechanical Phenomena; D007026:Hypothalamic Area, Lateral / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D007180:Incisor / Q000473:pathology; D007274:Injections, Intraperitoneal; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology; D009294:Narcotics / Q000008:administration & dosage / Q000494:pharmacology; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000473:pathology / Q000502:physiology; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology; D016761:Oncogene Proteins v-fos / Q000032:analysis / Q000187:drug effects; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques / Q000295:instrumentation
D009294:Narcotics; D016761:Oncogene Proteins v-fos; D009020:Morphine