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.

Perinatal undernourishment and handling: effects on olfactory discrimination in the newborn rat

“…), which achieves its adult characteristics only at the end of the third postnatal week. [5][6][7][8][9][10] Olfactory discrimination early in life coincides with the sensitive period of enhanced neuronal plasticity in the olfactory bulb. This activity is initially mediated by the maternal care and thereafter by nest environmental odors that induce important basic structural and functional plasticity for the pup's learning.…”

“…12 Furthermore, these alterations also affect olfactory structures (glomeruli profiles, mitral/tufted output, granule neurons, amygdala and hippocampal neuronal substrate), which delays the electrophysiological development and interferes with odor discrimination and long-term olfactory-guided behavior. 9,10,[25][26][27] During the lactating period, the mother-litter bonds are essential for the development of the newborn rat's physical, behavioral, cognitive, and endocrine responses to stress. [28][29][30] Maternal care can be disrupted if the lactating dam is exposed to stressful conditions.…”

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

“…[7][8][9][10] Most of these alterations occurred at the level of the neuronal dendritic arbor, as evidenced by significant reductions in the number of granule cells, and extensions of macroneuron dendritic prolongations, reduced number of spines, and decreasing area and perimeter of neuronal perikarya. 11 These postsynaptic olfactory alterations following early undernutrition suggest that neurogenesis is also dependent of olfactory cues deprivation as indicated by unilateral OB axotomy of olfactory receptor neurons that increases apoptotic cell death in the subventricular zone (SVZ) and along the rostral migration of neuroblasts differentiating into granular and periglomerular interneurons.…”

“…[14][15][16][17] Recently, we described reductions in the size of the olfactory glomeruli in different regions of the OB that were associated with neonatal undernourishment in the rat. 10 Based on these findings and with the aim of evaluating morphofunctional alterations associated with this noxious perinatal influence, we assessed morphological characteristics of the type II MC dendritic arbor and perikarya in neonatally undernourished rats. We hypothesized that, although MC originate in the last stage of gestation, their growth is, nevertheless, affected by neonatal undernourishment because their processes of neurogenesis, dendrogenesis and synaptogenesis are still passing through a critical stage until they achieve adult MC anatomical characteristics and stability in the OB laminar organization.…”

Development of the Gusto Facial Reflex in Perinatally Undernourished Rats

“…Perinatal undernutrition mainly interferes with the anatomical organization of central nervous system (CNS) areas which undergo a phase of postnatal cell proliferation; these areas include the cerebral and cerebellar cortices, the hippocampus, central amygdaloid nucleus, olfactory bulb, and solitary tract nucleus, and they participate in the head movements, mouth opening and closing, chewing, food ingestion, and chemosensory CNS integration [8,[9][10][11][12][13]. Early undernutrition affects neuronal development by reducing the cell number and their dendritic branching, and by the formation of spines with small perikarya alterations that interfere with their connectivity and neuronal interactions [7,8,[14][15][16].…”