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.

Perinatal malnutrition programs sustained alterations in nitric oxide released by activated macrophages in response to fluoxetine in adult rats.

OBJECTIVE: Nutritional restriction during lactation has long-term consequences on the functioning of neuroimmune systems. Receptors and transporter serotonin (5-HT) are present in macrophages and may influence their role. This study evaluated nitric oxide release by alveolar macrophages (AMs) in adult control rats and rats malnourished during lactation in response to different fluoxetine (FLX) concentrations and 5-HT(1A) and 5-HT(1B) agonists at different times. METHODS: Male Wistar rats were distributed into two groups according to maternal diet during lactation: a control group of 12 rats whose dams had received a 23% protein diet and a malnourished group of 12 rats whose dams had received an 8% protein diet. After weaning, all rats received a 23% protein diet. On the 90th day after birth, nitric oxide (NO) release kinetics was measured in supernatants of AMs cultured with FLX. The NO release following the adjunction of serotoninergic agonists was also quantified. RESULTS: The malnourished rats weighed less at weaning (control rats = 15.3 +/- 0.4 g, malnourished rats = 11.8 +/- 0.4 g); this difference persisted until 90 days of life (control rats = 355.4 +/- 8.6 g; malnourished rats = 267.8 +/- 7.9 g). In the presence of 10(-6)M FLX, NO release by AMs in control rats was lower. The addition of agonists did not interfere with NO release by AMs in control rats. NO release by AMs from malnourished rats was modified neither by FLX nor by agonists. As a consequence of malnutrition, there were lower numbers of cells and AMs in the bronchoalveolar lavage fluid, and cell viability and NO release by AMs were impaired. CONCLUSIONS: Nutritional manipulation in the perinatal period seems to interfere with the functional programming of macrophages; it also seems to affect their serotoninergic regulation through adulthood.