Pattern of Sucking Movements During Artificial Feeding of Neonatally Undernourished Rats

Effects of pre- and neonatal undernutrition on the kyphotic response and c-Fos activity in the caudal periaqueductal gray of primiparous lactating Wistar rats

In rodents, the most representative component of maternal behavior that meets the purpose of newborn nutrition is the kyphotic posture. During this posture, the mother maintains a unique environment for the protection, thermal regulation and breast-feeding of the progeny. The aim of this study was to investigate possible deficiencies in the kyphotic posture of adult lactating dams with pre- and neonatal undernutrition evoked by their own pups suckling in a home-cage situation. Wistar dams that had been previously exposed to perinatal undernutrition were mated at 90days of age, and pregnancy was confirmed by vaginal smears. Before testing if the perinatal underfed dam affected behavior, pups were removed (4h), and both the maternal response and the kyphotic posture were video-recorded (1h) and analyzed at 4 and 12days of lactation. Pre- and post-test litter weight gain was obtained. To immunostain the caudal periaqueductal gray, the litter was separated from their dams 24h before suckling stimulation. The results showed that underfed dams significantly reduced the duration of high kyphosis by choosing unconventional postures (prone and partial kyphosis). The body weight of the F1 offspring was significantly reduced, and the underfed F0 dams showed reduced c-Fos immunostaining at the caudal periaqueductal gray. The findings showed that early underfed dams have deficiencies in the mechanisms underlying the kyphosis, possibly because the pups' cues to evoke this posture were suboptimal and/or because the dam expressed deficient nursing. The results suggest that the abnormal kyphotic posture may affect the mother-litter bonds and have long-term effects on neonatal brain functions.

Maternal alterations induced by exposure to an unfamiliar home cage in early underfed dams

The expression of different behavioral components in the adult rat depends on a number of early influences, including age, hormones, manipulations of sensory cues, and perinatal undernutrition, all of which impact the development of brain areas underlying adaptive processes, maternal behavior, and the response to novelty. The current study investigates the effects of pre- and neonatal undernutrition on various components of maternal behavior of dams exposed to the challenge of an unfamiliar home cage on days 4, 8, and 12 of lactation. Food restriction was initiated from gestational day (G) G6 to G19 when dams received 50-70% of the normal balanced diet, followed by 100% from G20 to G21. After birth, pups were underfed by alternating every 12h between two lactating dams, one of which, had ligated nipples. Weaning was at 25days of age followed by an ad libitum diet until postpartum day 90, when females were mated, and subsequently tested for maternal behavior in an unfamiliar cage. The results indicated that in early underfed mothers the frequency of handling wood shavings and of, approaching, licking, crouching, and grasping pups for retrieval was significantly reduced. Moreover, self-grooming increased substantially in the underfed dams, but the frequency of rearing was reduced. Additionally, the body weight of pups nursed by early underfed dams was significantly lower than that of control pups. These findings suggest a relation between early food restriction and the deficient maternal care observed when these dams were challenged by exposure to an unfamiliar home cage.

Effects of perinatal undernutrition on the circumvallate papilla of developing Wistar rats

During the gestation and the lactating periods the gustatory papillae contain taste buds that respond to different flavors and aversive stimuli. The current study analyzed the effects of pre-and neonatal undernutrition on the circumvallate papillae of rats at 12, 20, and 30days of age. Early undernourishment occurred from gestational days G6 to G19 when dams received low percentages of food followed by a balanced diet from G20-21. After birth pups were underfed by rotating two lactating dams every 12h; in one of them, the nipples were tied. The pups were weaned at 25days of age, and then given an ad libitum diet. Under anesthesia the tongues were removed and stained with the hematoxylin-eosin (H-E) procedure. The results indicated that young underfed rats had significantly body weight reductions. The tongue measurements in underfed rats showed reduced total area and length of the anterior portion, but there were negligible effects on the posterior portion. The circumvallate papillae in underfed rats was significantly reduced in major length, major diameter, and total and upper areas, but unaffected in the lateral wall trench region. The taste bud areas and minor diameter were unaffected by undernutrition, but there were significant reductions in the total number of visible taste buds and the major diameter, delayed opening of taste bud pores, and an increased number of closed pores were also observed. These alterations by undernutrition reflect the vulnerability of structures in the gustatory oral cavity and suggest a possible interference with the receptorś activation, and transduction and perhaps with the taste encoding of signals to generate the gustatory sensory and hedonic responses.

Neonatal Food Restriction Induces Hypoplasia in Developing Facial Motor Neurons of Rats

The effects of neonatal food restriction upon the dendritic development of facial nucleus (FN) motor neurons of Wistar rats were analyzed. Rats neonatally underfed by daily (12 h) mother-litter separation in an incubator from 5-30 days after birth exhibited, in brain stem Golgi-Cox sections, significant reductions in the number and extension of stellate, triangular and bipolar FN neuronal dendritic prolongations with negligible effects upon perikarya measurements. Data suggest that in the underfed newborn, the ability of FN neurons to establish synaptic contacts with afferent fibers is reduced, which then interferes with their capacities for the integration and triggering of nerve impulses to modulate facial motor expression in response to sensory cues.

Alterations in the Solitary Tract Nucleus of the Rat Following Perinatal Food Restriction and Subsequent Nutritional Rehabilitation

Newborn of altricial species maintain functional gustatory communication with the mother because the neural substrate and the capacity to discriminate and promote gustofacial responses are already operating. Because little is known about the effects of perinatal food restriction upon gustatory neuronal brain stem structures, we characterized neuronal Golgi-Cox alterations of the solitary tract rostral portion (NSTr) where gustatory information is known to convey in neonatal Wistar rats. Pre-and neonatally undernourished rats exhibited a general reduction in the number and extension of distal dendrites particularly in small neurons but little effect upon perikarya measurements of the NSTr neuronal population. By contrast, in nutritional and sensory rehabilitated rats the number of distal dendrites increased, although the dendritic extensions were less affected compared to perinatally underfed and control subjects. The data indicate that perinatal food restriction interferes with the NSTr dendritic arbor organization, while nutritional and sensorial rehabilitation given by normally lactating dams induced plastic changes presumably modifying the integrative processes underlying early taste discriminative capabilities. Moreover, since perinatal food restriction is a powerful stressor influence and the NST forms a part of a complex system underlying adaptive stress responses, the neuronal alterations observed here may be partly due to this noxious perinatal influence.

Organization of olfactory glomeruli in neonatally undernourished rats

Newborn rats maintain mother-litter bonds by using olfactory signals. At birth, units in the olfactory glomeruli (OG) are immature and vulnerable to noxious epigenetic factors like undernutrition. Because little is known about the effects of neonatal undernutrition upon the OG morphological organization, different OG parameters were studied in undernourished Wistar rats at 7, 14 and 21 days of age. The issue was addressed by analyzing the olfactory bulb (OB) cross sectional area, the total number and area of OGs in the OB coronal sections, and the distribution of OG area in dorsal and ventral quadrants. Reductions in the OB and OG cross sectional areas were detected at 7 and 14 days posnatally. OG area comparisons by OB quadrants were reduced along the study in quadrants, with larger effects in medial than in lateral OB quadrants. Current OG cytoarchitectonic modifications may affect the newborn capabilities for odour discrimination by disrupting early mother-litter interactions.

A paradigm of undernourishing and neonatal rehabilitation in the newborn rat

Perinatal undernutrition as a deficiency of nutrient availability, affects body and brain developmental processes and promotes recurrent health problems. Thus, altered mother-litter bonds and deficient environmental interactions may interfere with the brain pluripotential capabilities of the newborn. To gather information concerning the mechanisms underlying perinatal undernutrition we designed a paradigm of undernutrition and neonatal rehabilitation in the rat. An underfed group came from pregnant Wistar rats fed with 50% of the diet from G6 to G12 and with 60% from G13 until G21. After birth, pups were daily undernourished during 12 h daily by rotating a pair of lactating well-nourished dams which had one of their nipples subcutaneously ligated. The rehabilitated animals were undernourished pups neonatally fed by a pair of normally lactating dams. Controls received plenty of food during the pre- and neonatal periods. Pups were sacrificed at 12, 20 and 30 days of age. Perinatal underfeeding significantly reduced body and brain weights and neuronal morphometric parameters. Normal neonatal feeding in the newborn ameliorated the damages associated to food deprivation. The current undernourishing paradigm may be helpful to assess brain development alterations, as well as to study the compensatory mechanisms associated to salutary epigenetic influences.

Neonatal nutritional rehabilitation of morphological features in facial motoneurons altered by prenatally food deprivation in the rat

Undernutrition alters facial motoneurons development. Here, we evaluated the plastic characteristics of facial motoneurons in response to neonatal rehabilitation. Prenatally undernourished rat pups derived from pregnant rats fed with 50% of the diet from gestational days G6 to G12, and with 60% of food from G13 to G21 and rehabilitated after birth by a pair of control lactating foster dams. Morphological features of 640 Golgi-Cox impregnated motoneurons from 12, 20 and 30 days old pups were analyzed. Neonatal food rehabilitation increased the number and extension of the dendritic branches (main neuronal reception area) without altering significantly soma measurements (main neuronal firing area), suggesting that food and sensory maternal disponibility after birth ameliorates the damage due to prenatal deprivation. Findings showed that neonatal rehabilitation in addition to intense maternal polysensorial stimuli from the foster mothers partially diminished the morphological alterations associated to prenatal undernutrition, and provide evidence of plastic properties of facial motoneurons to the influence of environmental cues.