Mirelta Regalado

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

Abstract 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.

Retrieving of Pups by Neonatally Stressed Mothers

Abstract In the rat, perinatal food and maternal deprivation provoke long-lasting effects upon the retrieving responses of dams to displaced pups. In the current study, the retrieving latency and the disruption in the body area of pups chosen by the mother to transport them to a new location was investigated on days 4, 8 and 12 postpartum in lactating Wistar rats. Rats, neonatally underfed by daily (12 h) mother-litter separation in an incubator from days 1 to 23 postpartum, exhibited prolonged retrieving latencies and disruption in the body area of young ones chosen by the dam to transport them to the nest. Furthermore, neonatally underfed dams frequently transported pups in a rude manner eliciting sonic distress cries from them compared to control mothers. These findings are possibly relevant to understand the impact of epigenetic influences on offspring brain and physiological maturation partly mediated through maternal care.

Maternal Responsiveness of Neonatally Undernourished and Sensory Stimulated Rats: Rehabilitation of Maternal Behavior.

The interaction between neonatal food deprivation and early sensory stimulation on four maternal behavioral components of Wistar strain rats was investigated. Dams neonatally underfed by daily mother-litter separation (Experiment 1), showed significant reductions in nest-rating and nursing time as well as increased retrieving latencies and selfgrooming responses compared to controls. Mothers which were neonatally undernourished by the nipple-ligation of their mothers (Experiment 2), exhibited less alterations in nest ratings, nursing time and retrieving latencies with no significant differences in the frequency of self-grooming responses, in comparison to controls. Neonatal handling and the exposure to a sensory enriched environment in Experiment 1, ameliorated most of the alterations of neonatally underfed mothers. Moreover, in Experiment 2, the increase in the neonatal sensory stimulation only improves nest ratings performance without consistent effects upon other maternal behavioral responses. Data suggest that sensory stimulation at critical stages of brain ontogeny is able to compensate long-term maternal behavioral deficiencies associated to a severe neonatal undernutrition (Experiment 1), with variable effects following a mild food intake deprivation (Experiment 2).

Dendritic Arbor Alterations in the Medial Superior Olivary Neurons of Neonatally Underfed Rats

Golgi-Cox-stained bipolar cells of the medial superior olive (MSO) were analyzed in control and undernourished Wistar strain rats at 12, 20, 30 and 40 days of age. Undernutrition significantly reduced the number of dendrites and the extension of ipsilateral dendritic prolongations, with no effects upon the cross-sectional somal area and minimal alterations in the corresponding contralateral dendritic branches. The data suggest that in underfed rate, afferents from the receptors projecting to the MSO via the anteroventral cochlear nuclei may cause an imblance in the binaural interactions which occur between the axon terminals and the ipsilateral contralateral dendritic arbors of MSO neurons.

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

Abstract 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.

Organization of olfactory glomeruli in neonatally undernourished rats

Abstract 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.

Movements restriction and alterations of the number of spines distributed along the apical shafts of layer V pyramids in motor and primary sensory cortices of the peripubertal and adult rat

The number and distribution of spines along apical shafts of rapid-Golgi-stained layer V pyramidal cells from visual, motor and somatosensory cortical areas were analyzed in control and movement-restricted (beginning at 20 days old) Wistar rats killed at 30, 40, 80 and 120 days of age (experiment A). In other group of rats, spine density was analyzed when restriction initiates on day 40 and the animals were killed at 50, 60 and 80 days postpartum, or after restriction starting on day 80 and killed at 120 days of age (experiment B). It has been found that the restriction of movements significantly reduces the total number of spines on apical shafts in the three cortical areas, when this condition starts at 20, 40 or 80 days without changing the overall distribution of spines. Also present findings indicate that the effects of movements restriction are attenuated when they were concurrent with maturational brain processes (20-40 days) than when they occurred later in life. The question remains open of which part of the measured reduction on the number of spines is due to the immobilization and which to the stress associated with this maneuver.

Pattern of Sucking Movements During Artificial Feeding of Neonatally Undernourished Rats

Alterations in the sucking activity of neonatally undernourished Wistar strain pups were observed by using a surrogate nipple procedure. Rats, neonatally underfed by daily (12h) mother-litter separation in an incubator from days 1–16 postpartum, showed a significant reduction in the mean number of sucking bouts within a 10min span, in the number of sucks per bout, prolonged significant time intervals between bouts and reduced mean duration of bouts when compared to controls. Moreover, the sucking bouts of neonatally underfed male and female pups were shorter and of poor efficiency compared to controls as far as body weight gain after each sucking test showed. These results suggest that perinatal undernutrition may affect both brain and muscle mandibular mechanisms to modulate sucking activity in the newborn.

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.

Recovery of long-term maternal behavioral deficiencies of neonatally underfed rats by early sensory stimulation: effects of successive parturitions.

The study examines the effects of two paradigms of neonatal food deprivation (daily mother-litter separation, Experiment 1 or nipple-ligation of mothers, Experiment 2) associated or not to early sensory stimulation (daily handling or the exposure to an enriched sensory environment) during the preweaning period of Wistar strain female rats. The effects of experimental manipulations were evaluated by measuring the nest building, retrieving latencies and nursing time of adult dams along three successive parturitions. Undernourished dams of Experiment 1, showed significant alterations in maternal responsiveness in the first delivery, which were attenuated by the maternal experience of two additional parturitions. Moreover, maternal alterations were importantly compensated by the association to early sensory stimulation (except nest building). Underfed mothers of Experiment 2 exhibited less alterations of the maternal response during the first parturition, and these were ameliorated by the maternal experience of successive parturitions. Additionally, complete recovery of maternal responsiveness alterations was obtained when sensory stimulation was associated to the maternal experience. Data suggest differential vulnerability to neonatal food and sensory deprivation of the neural mechanisms underlying maternal performance.