Neonatal low-protein diet reduces the masticatory efficiency in rats.
Little is known about the effects of undernutrition on the specific muscles and neuronal circuits involved in mastication. The aim of this study was to document the effects of neonatal low-protein diet on masticatory efficiency. Newborn rats whose mothers were fed 17% (nourished (N), n 60) or 8% (undernourished (U), n 56) protein were compared. Their weight was monitored and their masticatory jaw movements were video-recorded. Whole-cell patch-clamp recordings were performed in brainstem slice preparations to investigate the intrinsic membrane properties and N-methyl-d-aspartate-induced bursting characteristics of the rhythmogenic neurons (N, n 43; U, n 39) within the trigeminal main sensory nucleus (NVsnpr). Morphometric analysis (N, n 4; U, n 5) were conducted on masseteric muscles serial cross-sections. Our results showed that undernourished animals had lower numbers of masticatory sequences (P=0·049) and cycles (P=0·045) and slower chewing frequencies (P=0·004) (N, n 32; U, n 28). Undernutrition reduced body weight but had little effect on many basic NVsnpr neuronal electrophysiological parameters. It did, however, affect sag potentials (P<0·001) and rebound firing (P=0·005) that influence firing pattern. Undernutrition delayed the appearance of bursting and reduced the propensity to burst (P=0·002), as well as the bursting frequency (P=0·032). Undernourished animals showed increased and reduced proportions of fibre type IIA (P<0·0001) and IIB (P<0·0001), respectively. In addition, their fibre areas (IIA, P<0·001; IIB, P<0·001) and perimeters (IIA, P<0·001; IIB, P<0·001) were smaller. The changes observed at the behavioural, neuronal and muscular levels suggest that undernutrition reduces chewing efficiency by slowing, weakening and delaying maturation of the masticatory muscles and the associated neuronal circuitry.
1Graduate Program in Nutrition,Physical Activity and Phenotypic Plasticity,CAV,Federal University of Pernambuco,55608-680 Recife,Pernambuco,Brazil.
Kelli N
KN
Ferraz-Pereira
1Graduate Program in Nutrition,Physical Activity and Phenotypic Plasticity,CAV,Federal University of Pernambuco,55608-680 Recife,Pernambuco,Brazil.
Raquel
R
da Silva Aragão
3Département de Neurosciences and Groupe de Recherche sur le système Nerveux Central,Université de Montréal,Montréal, QC,H3C 3J7,Canada.
Dorly
D
Verdier
1Graduate Program in Nutrition,Physical Activity and Phenotypic Plasticity,CAV,Federal University of Pernambuco,55608-680 Recife,Pernambuco,Brazil.
Ana E
AE
Toscano
4Graduate Program in Physical Therapy,Federal University of Pernambuco,55608-680 Recife,Pernambuco,Brazil.
Diego C
DC
Lacerda
1Graduate Program in Nutrition,Physical Activity and Phenotypic Plasticity,CAV,Federal University of Pernambuco,55608-680 Recife,Pernambuco,Brazil.
Raul
R
Manhães-de-Castro
2Faculté de Médecine Dentaire and FRQS Network for Oral and Bone Health Research,Université de Montréal,Montréal, QC,H3C 3J7,Canada.
Arlette
A
Kolta
D000818:Animals; D000831:Animals, Newborn; D018753:Diet, Protein-Restricted / Q000009:adverse effects*; D055724:Electrophysiological Phenomena; D005260:Female; D007568:Jaw / Q000502:physiology; D008297:Male; D044342:Malnutrition / Q000473:pathology; D008409:Mastication / Q000502:physiology*; D016202:N-Methylaspartate / Q000009:adverse effects; D009474:Neurons / Q000378:metabolism; D018408:Patch-Clamp Techniques; D051381:Rats; D014278:Trigeminal Nuclei / Q000378:metabolism
D016202:N-Methylaspartate
AP action potential; GABA γ-aminobutyric acid; INaP sodium persistent current; Masseter muscle; Masticatory efficiency; N nourished; NMDA N-methyl-d-aspartate; NVsnpr trigeminal main sensory nucleus; RB regular bursts; Trigeminal nucleus; U undernourished; Undernutrition