Neonatal undernutrition and self-grooming development in the rat: long-term effects

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.

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.

Development of mitral cells and olfactory bulb layers in neonatally undernourished rats

Cell alterations in the central nervous system are consistent consequences of early undernourishment. Because little is known about the effects of neonatal udernourishment upon the main olfactory bulb (OB) in Golgi-Cox stained material, we evaluated the total OB cross-sectional area, the area of individual OB layers, and the area of type II mitral cells perikarya and their dendritic processes in undernourished Wistar rats of 7, 14, and 21 days of age. Data showed that neonatal undernourishment reduced both the OB and the individual layers areas; minimal perikarya effects and significant reductions in the number and extension of MC dendrites. Although macroneurons are formed prenatally, neonatal undernourishment at critical periods may have long-lasting effects that interfere with the functional maturity of the OB. These findings may have relevant consequences for early odor discrimination of the offspring, since olfaction is a fundamental sensorial avenue for newborn adaptive responses and maternal care.

Contributions of undernutrition and handling to huddling development of rats

When newborn rats are separated from the mother, they consistently exhibit the huddling response to maintain body temperature and physical contact. Therefore, we investigated if preweaning handling/sensory stimulation may overcome the huddling deficiencies associated to neonatal undernourishment/maternal deprivation of Wistar rats maintained at constant temperature (30 degrees C). The data indicated that initial and final temperatures in the pile of undernourished (U) and undernourished stimulated (Us) pups was reduced compared to their controls (C and Cs, respectively). Huddling latency was prolonged at 5 days of age in the Us group and at 20 days of age in the U pups. On postpartum day 5, U and Us subjects were similar in battery and pile-huddling performance compared to their controls; thereafter, the frequency of battery type was low and pile type was high (in frequency) in all experimental treatments. The frequency of recycling from the pile in the Us pups in most of the ages was significantly reduced compared to U and C subjects, suggesting that early sensory stimulation possibly accelerates the maturation of thermoregulatory brain structures underlying the huddling response and causing increased physical contacts. The data provide evidence that both neonatal undernutrition/maternal deprivation and early sensory stimulation may modify the huddling response by reducing or increasing, respectively, brain mechanisms underlying huddling. The amount of physical contact the newborns receive from their littermates and the mother may be a fundamental source of sensory cues for neuronal maturation and brain functioning.

Neonatal food restriction and binaural ear occlusion interfere with the maturation of cortical motor pyramids in the rat

Golgi-Cox-impregnated pyramidal neurons of layer five motor cortical area were investigated in control, binaural ear-occluded control, undernourished and binaural ear-occluded undernourished Wistar rats of 12, 20 and 30 days of age. In neonatally undernourished, binaural ear-occluded-undernourished and partly in ear-occluded-control subjects, there were significant reductions in both the number and extent of the distal part of the dendritic branches of motor pyramids compared to their controls. Moreover, minimal effects on perikarya measurements were observed. These findings suggest that neonatal undernutrition and the concurrent reduction of auditory cues affect dendritic arbor development and possibly the convergence of the auditory experience upon motor pyramids and may interfere with the neocortical modulation of postural and movements activities.

Effects of neonatal undernutrition and binaural ear occlusion on neuronal development of the superior olivary complex of rats

Golgi-Cox-impregnated neurons of the superior olivary complex were investigated in control, binaural ear-occluded control, undernourished, and binaural ear-occluded undernourished Wistar rats of 12, 20, and 30 days of age. In neonatally undernourished and binaural ear-occluded animals, a significant reduction in the number of dendrites and dendritic intersections in the medial trapezoid body neurons was observed. Inconsistent effects upon the dendritic arbor lateral superior olivary cells were also detected. Control and undernourished rats with binaural ear occlusion exhibited a significant increase in the dendritic arbor measurements of lateral superior olivary neurons as compared with the cells of the medial trapezoid body. The cytoarchitectonic imbalance between the modulatory efferent control of these systems and the sensory auditory input to the cochlea may be important for the integration of complex auditory physiological phenomena.

Two peptidergic drugs increase the synaptophysin immunoreactivity in brains of 6-week-old rats

An increase of synaptic density has been found in the hippocampus, the dendate gyrus and in the entorhinal cortex of 6-week-old rats after 7 days of treatment with the peptidergic drug Cerebrolysin, its peptide preparation E021 and the diluted peptide preparation E021dil. Rats received drugs on postnatal days 1-7 (2.5 ml/kg, each day). Controls received saline. The animals were sacrificed on days 42-48 of their life, after they had undergone behavioural testing in a Morris water maze. Slices of brain were stained immunohistochemically with anti-synaptophysin, a specific marker of presynaptic terminals. The synaptophysin-immunoreactivity of presynaptic terminals was quantified using light microscopy and a computerised image analysis system. Our results showed that rats benefit from the treatment with both drugs. A significant increase in the number of synaptophysin-immunoreactive presynaptic terminals was found in the entorhinal cortex and the hippocampal subfields CA1, CA2, CA3 stratum radiatum and CA3 stratum lucidum. The increased immunoreactive presynaptic terminals found in the present study are in accordance with the positive effects of the drugs on spatial learning and memory in young rats (Gschanes & Windisch 1999).

Development of play behavior in neonatally undernourished rats

The effects of neonatal food and sensory deprivation on play social behavior (boxing, wrestling, and pinning) were studied in male and female Wistar strain rats from 20 to 60 days of age. Data showed that the mean frequency of total play was markedly increased in neonatally underfed subjects. Play did also increase in the females and during the interaction in pairs and in the play that occurred during the prepuberal period. These findings suggest that early food restriction and the unavoidable sensory deprivation associated to the undernourishing procedure, interfere with the neuroendocrine maturational processes of central and peripheral modulatory mechanisms underlying play behavior.

Neurotoxicology and amino acid intake during development: the case of threonine

The development of the central nervous system is highly dependent on an adequate supply of nutrients. In particular, protein and amino acid availability is of major concern during gestation and in early postnatal life. Numerous data have been published on some amino acids directly involved in brain functions as neurotransmitters or indirectly as precursors of neurotransmitters, but scant information is available on the possible consequences of hyperthreoninemia, a phenomenon repeatedly noted in clinical reports. The results of neurochemical and behavioral studies in the developing rat suggest that despite numerous possible effects of threonine on brain constituents, moderate hyperthreoninemia does not impair markedly the development of the central nervous system.

Chronic tryptophan restriction disrupts grooming chain completion in the rat

Tryptophan restriction in the diet leads to low levels of brain serotonin. Serotonin has been implicated in the magnitude of novelty-induced grooming behavior, but its possible role in self-grooming chain completion has not been investigated. A tryptophan-deficient diet produced fewer chain-associated face washings, more face washings alone, fewer number of chains, as well as elementary units into chains. Thereafter, an apparent lower threshold for emotional responsiveness also took place. Impairments of the serotoninergic inhibitory activity of striatal and/or nigral dopaminergic terminals is suggested, because corpus striatum has been proposed to be an organizer structure of both the serial ordering as well as in the completion of the self-grooming chains.

Neonatal capsaicin administration: effects on behavioral development of the rat

The effect of a single dose of capsaicin administered neonatally on the development of six motor behavioral patterns (scratching, rearing, grooming, searching, remaining still, and sniffing) was examined in Wistar rats. Treated animals exhibited a significant increment in scratching, rearing, grooming, and searching. Capsaicin also provoked precocious eye opening of one to two days and a reduction in remaining still, sniffing, and body weight. These effects were accompanied by pelage dishevelment and presence of skin ulcers in the region of the head, neck, and shoulders. The distribution of skin ulcers suggests that the fifth cranial nerve and roots innervating C1-C3 spinal cord segments contain a high proportion of capsaicin-sensitive "C" and A delta fibers.