Effects of Perinatal Undernutrition and Massage Stimulation upon the Ambiguus Nucleus in the Rat Prior to Weaning

Undernutrition produces morphological brain alterations and cognitive deficiencies in children of underdeveloped countries. The central nervous system (CNS) alterations mainly interfere with the anatomical organization of areas undergoing a phase of intense postnatal cell proliferation, disrupting plastic processes like learning, memory, and phonation. In the rat pup, prenatal malnutrition interferes with the elaboration of ultrasonic vocalizations (USVs) by poorly understood mechanisms. The neuronal caudal portion of the nucleus ambiguus (Ambc) innervates the laryngeal intrinsic muscles to produce phonation, a basic USV communication system. During postnatal development, enhanced plasticity phenomena play a fundamental role in improving brain function. Thus, the massage stimulation (MS) may accelerate growth and induce neurogenesis in different areas of the brain. The current study analyzed the effects of a daily 10-min MS on the dendritic tree and perikarya measurements of Ambc multipolar motoneurons (Golgi-Cox) of perinatally underfed (U), control (C), control massage-stimulated (CMS), and underfed massage-stimulated (UMS) groups at postnatal days (PDs) 8, 12, and 15. The data indicated that the dendritic scores were reduced (p < 0.05) in both number and density at PD8 and PD15 in the U subjects and that MS increased the values of these parameters (p < 0.05). In addition, MS induced body weight gain in both U and CMS groups, and it enhanced the dendritic density in CMS subjects. These results show that MS during the pre-weaning period restores the plastic properties of the Ambc over the hypoplastic multipolar motoneuron after the alterations caused by perinatal undernutrition.

Retrieval of Pups by Female Rats Undernourished during the Pre- and Neonatal Period

Early mother-litter bonds alterations elicited by pre- and neonatal undernutrition are a source of long-lasting brain and functional disorders such as exploratory and emotional deficits and maternal unresponsiveness to the newborn. Here, we examined the prolonged effects of gestational and neonatal food restriction on the retrieval of pups and nest building activity by primiparous adult Wistar rats on postnatal days (PDs) 4, 8, and 12. In early undernourished dams, the latency to retrieve the first or the fifth pups in the litter was extended;and nest building activity was significantly reduced. Additionally, early underfed dams retrieved the pups in a rough manner, eliciting distress cries and grasping the pups by unusual body areas. The current findings suggest that pre- and neonatal food restriction may affect the anatomical and functional forebrain structures, modulating the cognitive and motor components underlying maternal responsiveness.

Neuronal c-Fos Reactivity of Medial Prefrontal Cortex and Basolateral Amygdala in Perinatally Underfed Lactating Wistar Rats

Pre- and neonatal food restriction interferes with the neuronal and functional organization of longterm social adaptive responses including the maternal response to ensure pup survival. We addressed this issue by using low percentages of food from gestational days G6 to G 19 (50% to 30%) followed by a balanced diet from G20 to G21. After birth, pups were underfed by rotating two lactating dams, one with tied nipples, every 12 h. Weaning was at 25 days of age and thereafter an ad libitum diet. The F1 dams’ motivation (pup retrieval, handling shavings and crouching) was evaluated (10 min) at 4 and 12 days of lactation, when they had reached 90 days of age. The maternal neuronal functionality was measured by immunostaining the medial prefrontal cortex and the basolateral amygdala when the pups were removed from their dams 90 min after suckling. Underfed dams exhibited significantly lower pup retrieval, handling shavings and crouching frequencies, as well as prolonged latencies for pup retrieval and for handling shavings and crouching. Furthermore, early underfed dams had Fos-I neuron deficiencies mainly in the pre-frontal cortex, with minor effects on the amygdala, possibly because the pups’ cues to elicit maternal motivation were suboptimal and/or because of the deficient network activation.

Parabrachial neuron development: Effects of pre- and neonatal undernutrition in the rat

Pre-and neonatal fasting in the rat has been used as an experimental model to obtain information on how the newborn gustatory system can be damaged, in- terfering with the basic sensory and hedonic proc- esses to different tastants. Fasting during the prenatal period and for 24 days postnatally results in signifi- cant reductions of body and brain weight, number of branches, dendritic density, and cross-sectional area of the PBN multipolar neurons in the central lateral and central medial subnucleus particularly at post- natal days 20 and 30. Furthermore, the underfeeding paradigm affected more the middle portions of the dendritic tree than other parts of the neurons possibly disturbing the afferent characteristics of neuronal acti- vity propagation that may partly disrupt the elabora- tion of synaptic plasticity at later ages. These findings may play a role in the development of complex physio- logical phenomena such as food intake, taste discrimi- nation, learning taste aversion, and appetitive beha- vior.

Effects of Pre-and Neonatal Undernutrition on Long-Term Hearing Cognition of the Rat

Experimental evidence in the rat suggests that perinatal undernutrition, associated with sensory and hormonal deficiencies, interferes with brain network integrative actions. We review peripheral and central morpho-functional alterations related to early food restriction along with the auditory relays, and their connections with the limbic system, which are essential for motivation-emotional arousal. The findings indicated that different morpho-functional alterations in the auditory system permanently affect the brainstem, the reticular thalamic nucleus, and the prefrontal and auditory cortices. Moreover, data showed the noxious role of early food restriction and the external ear occlusion on the distal portions of dendritic arbor measurements, in the cochlea, nucleus ambiguous and motor cortical pyramids. These anatomical alterations also correlated with deficiencies in the dynamic motor and auditory cognitive brain plasticity. Food restriction-related deficiencies in the motor-emotional-behavioral arousal systems may be useful to understand long-term cognitive disorders in humans.

Effects of Neonatal Undernutrition on Development of the Dorsolateral Prefrontal Cortex Pyramidal Cells in the Rat

The dorsolateral prefrontal cortex (dlPFC) of the rat plays a role in the encoding of neuronal signals involved in conflict-induced behavioral adjustment, working memory, planning and executive abilities, attentional control and other cognitive responses. In altricial species, early perinatal undernutrition interferes with the morphofunctional organization of a number of central nervous system (CNS) structures including the prefrontal cortex. The effects of neonatal undernutrition on dendritic arbor density, perikaryon measurements, and the number of spines (detected by rapid-Golgi) of basilar dendritic segments in layer III pyramidal neurons of the dlPFC were examined in male Wistar rats on postnatal (PDs) 12, 20, and 30. In the underfed (U) subjects the distal portions of the dendritic arbors had a consistent hipoplasia, mainly on PD 30, with reduced cross sectional area, perimeter, and spine densities on the basilar dendrites on all days studied. Thus, the alterations of the dlPFC pyramidal neurons may interfere with the plastic synaptic activity and cognitive performance of rats subjected to the stress of early underfeeding. Characterizing these anatomical alterations may help to understand the disrupted cognitive processes associated with neonatal undernutrition.

Juvenile Play Behavior in Neonatally Underfed and Sensory Stimulated Wistar Rats

Play development in juvenile rats depends on specific sensory signals integrated at cortical, limbic and brain stem levels to modulate motoric, metabolic, motivational and social responses. Neonatal undernourishment disrupts the morphological and functional organization of the brain for adaptive responses including play performance. These alterations may be restored by preweaning exposure to sensory-enriched environments. This study was designed to determine in four experimental groups, Control (LC), Underfed (LU), Control Ligated/Stimulated (LCS), and Underfed Ligated/Stimulated (LUS), whether changes in juvenile play of neonatally underfed male rats by the nipple-ligated procedure of F0 dams and/or the handling of F1 rats may restore the deficiencies in juvenile play performance. The pinning frequency values in LC, LCS and LUS groups consistently increased until reaching a significant peak between postnatal days (PDs) 25 and 50 and then gradually declining until PD 60, when the play in pairs was significantly higher compared with the play in groups that follows the same sequence but with lower values in the stimulated groups. The results may reflect poor maternal care and lower somatosensory stimulation;and the sensory massage of LU F1 pups compared with the LC, LUS, and LCS rats. Fewer dorsal body contacts occurred in LU and LUS rats when playing in pairs than in groups. Results suggest that although handling has salutary effects on neuronal play structures, the reduced levels of total pinning and dorsal contacts, mainly in the play of rat pairs in LCS vs. LUS groups, were not fully recovered.

Maternal Response of Perinatally Underfed Wistar Virgin Females Exposed to Newborn Rats

Nutrition plays a major role in the survival of the progeny, and its perinatal deficiencies delay physical development and interfere with social and cognitive performance later in life. The effects of early undernutrition on maternal social performance of sensitized adult virgin rats were evaluated. Several maternal and non-maternal responses were measured in virgin female Wistar rats randomly divided into two groups, control and early undernourished, during 19 days of chronic daily exposure to fresh foster pups in home-cage conditions. Underfed females (F0) received different percentages of a balanced diet during gestation. After birth, pups were underfed (F1) by alternating every 12 h between litters two lactating dams, one with ligated nipples. Weaning was at 25 days of age followed by an ad lib diet until postpartum day 90, when sensitized virgins were maternally tested daily for seven successive sessions. Significantly (p < 0.05) low body weight scores in UG F1 virgins of five different ages were observed. The UG F1 females expressed significantly (p < 0.05) lower frequency values in sniffing, licking, retrieving, crouching, and handling shavings, with clear prolonged sniffing, retrieving and handling shaving latencies towards the foster pups compared with CG F1 sensitized females. Self-grooming was not affected, whereas exploration was significantly reduced. Current findings suggest that perinatal undernutrition interfered the organization of a core neuronal circuitry underlying the mother-litter interactions involved in social and cognitive performance of sensitized adult virgins. Furthermore, the behavioral maternal alterations in F1 virgins may possibly generate a risky negative social environment to induce cognitive and/or brain disorders in later generations.