Environmental deprivation delays the maturation of motor pyramids during the early postnatal period

Influence of antenatal synthetic glucocorticoid administration on pyramidal cell morphology and microtubule-associated protein type 2 (MAP2) in rat cerebrocortical neurons

Previous animal studies have indicated that excessive prenatal circulating glucocorticoid (GC) levels induced by the antenatal administration of synthetic GC (sGC) significantly alter neuronal development in the cerebellar and hippocampal neurons of the offspring. However, it is unknown whether antenatal sGC administration results in long-term neocortical pyramidal cell impairment. In the current study, we examined whether an equivalent therapeutic dose of antenatal betamethasone phosphate (BET) in pregnant rats alters the Golgi-stained basilar dendritic length and histochemical expression of dendritic microtubule-associated protein 2 (MAP2) of neocortical pyramidal cells in infant, adolescent, and young adult offspring. The results obtained showed that in utero BET exposure resulted in a significant reduction in the basilar dendritic length per neuron and a transient reduction in histochemical MAP2 immunoreactivity. Consistent with previous hippocampal and cerebellar data, the present findings suggest that prenatal BET administration alters the dendritic growth of cerebrocortical pyramidal cells.

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.

A morphometric study on the early stages of dendrite changes in the axotomized motoneuron of the spinal cord in newborn rats

OBJECTIVES

To study the early effect of axotomy on spinal motoneurons and dendritic trees in the newborn rat.

METHODS

The left sciatic nerve of 50 neonatal Sprague--Dawley rats aged 5 days old was transected and the right area kept as a control. The operated animals were killed 2, 4, 8, 12 and 24 hours after axotomy. The L4--L6 segments of the spinal cord were sampled, and stained either with Golgi-Cox or Cresyl fast violet methods. The number of motoneurons, the largest soma diameter and the different parameters of the dendritic trees such as: number, length and thickness of the primary, secondary and tertiary branches in the axotomized sides were estimated and compared statistically with that of the intact sides.

RESULTS

The results indicated that in the axotomized sides, the number of motoneurons and the largest soma diameter were decreased, but these were significant only in 12- and 24-hour groups. The number of branches of the dendritic trees including primary, secondary and tertiary branches was not significantly decreased in the groups. The thickness of the dendrites showed a reduction; however, this was significant only for the tertiary branches in the 24-hour groups. The length of the primary, secondary and tertiary branches of the dendrites--especially the latter--were also decreased significantly in most of the groups.

CONCLUSION

Axotomy at the early stages in newborn rats resulted in noticeable morphometrical changes in motoneurons and their dendrites.

Frequency Modulation and Spatiotemporal Stability of the sCPG in Preterm Infants with RDS

The nonnutritive suck (NNS) is an observable and accessible motor behavior which is often used to make inference about brain development and pre-feeding skill in preterm and term infants. The purpose of this study was to model NNS burst compression pressure dynamics in the frequency and time domain among two groups of preterm infants, including those with respiratory distress syndrome (RDS, N = 15) and 17 healthy controls. Digitized samples of NNS compression pressure waveforms recorded at a 1-week interval were collected 15 minutes prior to a scheduled feed. Regression analysis and ANOVA revealed that healthy preterm infants produced longer NNS bursts and the mean burst initiation cycle frequencies were higher when compared to the RDS group. Moreover, the initial 5 cycles of the NNS burst manifest a frequency modulated (FM) segment which is a significant feature of the suck central pattern generator (sCPG), and differentially expressed in healthy and RDS infants. The NNS burst structure revealed significantly lower spatiotemporal index values for control versus RDS preterm infants during FM, and provides additional information on the microstructure of the sCPG which may be used to gauge the developmental status and progression of oromotor control systems among these fragile infants.

Suck Predicts Neuromotor Integrity and Developmental Outcomes

Neonatal motor behavior predicts both current neurological status and future neurodevelopmental outcomes. For speech pathologists, the earliest observable patterned oromotor behavior is suck. Suck production requires effective coordination of an infant's oral sensorimotor system and is subject to a variety of neuromodulatory inputs. Demonstration and practice of coordinated suck serves as a biomarker for oral feeding skills neural integrity and is being assessed for its relation to neurodevelopmental outcomes (speech, cognition, and learning) by research teams in the United States, Europe, Japan, and Brazil. Suck may also serve as an intervention point to prevent feeding disorders and mitigate speech-language delays and disorders.

Respiratory treatment history predicts suck pattern stability in preterm infants

Sensory deprivation and motor restriction associated with extensive oxygen therapy may lead to poor oromotor control in preterm infants. Non-nutritive suck is one of the first complex oromotor behaviors infants perform. This study determined the spatiotemporal variability of non-nutritive suck (NNS) pressure trajectories in three preterm groups with differing oxygen histories-one control group with minimal or no O(2) therapy, and two Respiratory Distress Syndrome (RDS) groups with either a mild/moderate (RDS1) or moderate/severe (RDS2) O(2) history. The Non-nutritive Suck Spatiotemporal Index (NNS STI) quantifies spatial and temporal variability across kinematic trajectories, and was calculated from digital representations of infants' suck pressure signals. An ANCOVA revealed a significant effect for group (p < .001) on the NNS STI measure, with RDS2 infants showing highly variable NNS patterning, and thus relatively underdeveloped suck. Extensive oxygen therapy, which alters the oral sensory environment and reduces motor experiences, disrupts the development of coordinated NNS in preterm infants.

Synthetic orocutaneous stimulation entrains preterm infants with feeding difficulties to suck

BACKGROUND

Prematurity can disrupt the development of a specialized neural circuit known as suck central pattern generator (sCPG), which often leads to poor feeding skills. The extent to which suck can be entrained using a synthetically patterned orocutaneous input to promote its development in preterm infants who lack a functional suck is unknown.

OBJECTIVE

To evaluate the effects of a new motorized 'pulsating' pacifier capable of entraining the sCPG in tube-fed premature infants who lack a functional suck and exhibit feeding disorders.

METHODS

Prospective cohort study of 31 preterm infants assigned to either the oral patterned entrainment intervention (study) or non-treated (controls) group, matched by gestational age, birth weight, oxygen supplementation history and oral feed status. Study infants received a daily regimen of orocutaneous pulse trains through a pneumatically controlled silicone pacifier concurrent with gavage feeds.

RESULTS

The patterned orocutaneous stimulus was highly effective in accelerating the development of non-nutritive suck (NNS) in preterm infants. A repeated-measure multivariate analysis of covariance revealed significant increases in minute rates for total oral compressions, NNS bursts, and NNS cycles, suck cycles per burst, and the ratiometric measure of NNS cycles as a percentage of total ororhythmic output. Moreover, study infants also manifest significantly greater success at achieving oral feeds, surpassing their control counterparts by a factor of 3.1 x (72.8% daily oral feed versus 23.3% daily oral feed, respectively).

CONCLUSION

Functional expression of the sCPG among preterm infants who lack an organized suck can be induced through the delivery of synthetically patterned orocutaneous pulse trains. The rapid emergence of NNS in treated infants is accompanied by a significant increase in the proportion of nutrient taken orally.

Non-Nutritive Suck Parameter in Preterm Infants with RDS

OBJECTIVE: To characterize the integrity of non-nutritive suck (NNS) parameters among three groups of preterm infants ranging from normal to those with progressive degrees of respiratory distress syndrome (RDS). STUDY DESIGN: NNS compression waveforms were sampled from 55 infants in the neonatal intensive care unit using a silicone pacifier electronically instrumented for intraluminal pressure. Seven select NNS parameters were measured at two different sessions, and statistically analyzed using a General Linear Model Analysis of Covariance. RESULTS AND CONCLUSIONS: Preterm infants with a more extensive history of RDS and oxygen therapy manifest significantly (p≤0.001) degraded performance on six of the seven NNS measures. This trend was disproportionately amplified in preterm infants with moderate-to-severe RDS. Prolonged periods of RDS requiring oxygen therapy may cause maladaptive orosensory experiences, and restrict oral movements which may contribute to delayed NNS development.

Respiratory Distress Syndrome Degrades the Fine Structure of the Non-Nutritive Suck In Preterm Infants

AIMS AND OBJECTIVES: Suck development is a challenging hurdle for preterm infants who endure an extensive oxygen history due to respiratory distress syndrome (RDS). The fine structure of the non-nutritive suck (NNS) was studied in preterm infants according to RDS severity. DESIGN AND METHODS: Recordings of NNS were completed cribside in the neonatal intensive care unit (NICU) in 55 preterm infants distributed among one healthy control group and two RDS infant groups. NNS pressure amplitude (cmH(2)0) and within-burst suck cycle period (ms) were the dependent measures extracted from digitized records of pacifier nipple compression pressure. RESULTS AND CONCLUSIONS: RDS preterm infants demonstrated significant differences in NNS suck pressure amplitude compared to healthy preterm infants. Periods of oxygen supplementation restrict orofacial movement and limit orosensory experiences necessary for suck development and neural maturation. RDS infants may be excellent candidates for patterned oral stimulation programs designed to advance the maturation of sucking skills.

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.

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.

NADPH-d positive neurons in the developing somatosensory cortex of the rat: effects of early and late environmental enrichment

The effects of environmental enrichment upon the topographic arrangement of NADPH diaphorase-positive neurons (NADPH-d+ neurons) was studied in the somatosensory cortex of 56 Sprague-Dawley albino rats during early stages of development (18th, 24th, 30th and 60th postnatal days). This diaphorase is easily demonstrable, providing a convenient marker for quantitative studies. Environmental enrichment diminished the number of NADPH-d+ neurons and exerted its maximal influence during lactation, a time of exceptional cortical susceptibility. This implies that the magnitude of such effects on the density of NADPH-d+ neurons is age-dependent. Furthermore, it was found that the experience-dependent cortical changes persisted after a subsequent period without environmental stimulation. The effects of early environmental enrichment did not occur uniformly throughout the cerebral hemispheres but, instead, such effects were maximal in the latero-ventral sector of the cerebral cortex where a dramatic reduction in the number of NADPH-d+ neurons was observed. Particularly striking was the existence of a latero-medial sequence of NADPH-d+ neurons in the infragranular layer and a reversed distribution of labeled cells, in the supragranular layer. Both ontogenetic sequences of NADPH-d+ neurons remained unchanged during postnatal development in controls and enriched subjects (18th-60th postnatal days).