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

Abstract

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 imbalance in the binaural interactions which occur between the axon terminals and the ipsilateral and contralateral dendritic arbors of MSO neurons.

Effects of Neonatal Undernutrition and Binaural Ear Occlusion on Neuronal Development of the Superior Olivary Complex of Rats

“…The finding of neuronal MTB and LSO dendritic arbor alterations associated with neonatal undernutrition and ear binaural occlusion provided new information on the plastic cytoarchitectonic reorganization of the first synaptic relays of the auditory system. Regarding this, the present data agree with the results of other studies showing that visual and somatosensory cues deprivation decreases, while polysensorial stimulation increases the dendritic arborizations of neurons in motor pyramids [39], visual cortex [40,41], claustrum [42], amygdala [8], hippocampus [43], and medial superior olivary neurons [33]. Moreover, there is a sharp increase in the number of spines or dendritic branching after renutrition or ear and eye opening.…”

“…4, 5) may first be explained by the prolonged time of sound transmission in bone provoked by the binaural ear occlusion with the rubber glue that promotes the neuronal LSO dendritic arbor maturation and its modulatory projection on the inner hair cells of the organ of Corti [31][32][33]. This fact correlates well with the late MTB neuronal maturation primarily associated with the air-sound transmission when the auditory channel is opened [31].…”

“…2, 3, 5) may be explained on the basis of the close correlation between time and the neonatal origin of MTB contralateral projections (days 1-15 of age) to the outer hair cells [23,31] which increases the possibility of a cytoarchitectonic alteration provoked by neonatal undernutrition on MTB neurons [32,33]. In the same context, the negligible reductions provoked by early undernutrition in number and extension of dendritic prolongations of the LSO neuronal population may be related to the accelerated development of their ipsilateral projections (days 1-10 of age) to the inner hair cells of the organ of Corti [21,31] which reduces the possibility of LSO neuronal dendritic arbor damages associated with neonatal food deprivation ( fig.…”

“…This possible functional imbalance may result in an increased input through outer hair cell as compared with inner hair cell entry, affecting the auditory binaural interactions at the supraolivary levels [34,35]. This assumption is reinforced by pre-vious electrophysiological and morphological studies performed in the auditory channel of both underfed children and early food-restricted rats, suggesting a failure in the development of mechanisms underlying the control of auditory cues input during the habituation and attention span [18,33,36].…”

Development of the Gusto Facial Reflex in Perinatally Undernourished Rats

“…In the past, a number of studies have shown that perinatal undernutrition in the rat delays the maturation of sensory systems and causes the expression of altered motor patterns; these effects lead to a significant deficiency of somatosensory, auditory, visual, and chemosensory stimulation that may be essential for long-term behavioral performance [1][2][3][4][5][6][7][8]. 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].…”