title: Effects of a liquid diet on the response properties of temporomandibular joint nociceptive neurons in the trigeminal subnucleus caudalis of growing rats.
abstract: OBJECTIVE
  To investigate whether low mechanical loading on the temporomandibular joint (TMJ) when ingesting a liquid diet affects the response properties of neurons in the trigeminal spinal tract subnucleus caudalis (Sp5C) in growing rats.
  
  
  METHODS
  Shortly after weaning, 2-week-old male rats were fed chow pellets (control) or a liquid diet (experimental). Firing activities of single sensory units were recorded from the Sp5C at 4, 5, 7, and 9 weeks. Neurons were functionally classified by their responsiveness to TMJ stimuli. The responses of Class II and III neurons to TMJ stimuli were investigated.
  
  
  RESULTS
  In both neuron classes, the firing threshold in the experimental group was significantly lower than in the control group at all time points, but remained static in the control group throughout the experimental period, whereas it peaked in the experimental group at 4 weeks, decreased at 5 weeks, and remained stable thereafter until 9 weeks. Similarly, the initial firing frequency was significantly higher in the experimental group than in the control group, but remained static in the control group throughout the experimental period, whereas in the experimental group, it was at its lowest at 4 weeks, increased at 5 weeks, and stayed stable thereafter until 9 weeks.
  
  
  CONCLUSIONS
  Differences in TMJ loading arising from variable diet consistency during growth may affect the functional characteristics of Sp5C neurons.
authors.affiliation: Orthodontic Science, Department of Orofacial Development and Function, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Hiranuma
authors.forename: S
authors.initials: S
authors.lastname: Kokai
authors.forename: K
authors.initials: K
authors.lastname: Fujita
authors.forename: T
authors.initials: T
authors.lastname: Ishida
authors.forename: M
authors.initials: M
authors.lastname: Shibata
authors.forename: S
authors.initials: S
authors.lastname: Naito
authors.forename: T
authors.initials: T
authors.lastname: Yabushita
authors.forename: T
authors.initials: T
authors.lastname: Ono
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005526:Food, Formulated; D017746:Joint Capsule / Q000294:innervation; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D009619:Nociceptors / Q000145:classification / Q000502:physiology*; D010812:Physical Stimulation; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D009435:Synaptic Transmission / Q000502:physiology; D013704:Temporomandibular Joint / Q000294:innervation*; D014110:Touch / Q000502:physiology; D014275:Trigeminal Caudal Nucleus / Q000502:physiology*; D014276:Trigeminal Nerve / Q000502:physiology
keywords: Sp5C; Temporomandibular joint; liquid diet; nociceptive neuron; rat