TY - JOUR
T1 - Morphology of developing rat genioglossal motoneurons studied in vitro
T2 - Changes in length, branching pattern, and spatial distribution of dendrites
AU - Nüñez‐Abades, P. A.
AU - He, F.
AU - Barrionuevo, G.
AU - Cameron, W. E.
PY - 1994/1/15
Y1 - 1994/1/15
N2 - The aim of this study is to describe the postnatal change in dendritic morphology of those motoneurons in the hypoglossal nucleus that innervate the genioglossus muscle. Forty genioglossal (GG) motoneurons from four age groups (1–2, 5–6, 13–15, and 19–30 postnatal days) were labeled by intracellular injection of neurobiotin in an in vitro slice preparation of the rat brainstem and were reconstructed in three‐dimensional space. The number of primary dendrites per GG motoneuron was ∼6 and remained unchanged with age. The development of these motoneurons from birth to 13–15 days was characterized by a simplification of the dendritic tree involving a decrease in the number of terminal endings and dendritic branches. Motoneurons lost their 6th–8th order branches, in parallel with an elongation of their terminal dendritic branches maintaining the same combined dendritic length. The elongation of terminal branches was attributed to both longitudinal growth and the apparent lengthening caused by resorption of distal branches. The elimination of dendritic branches tended to increase the symmetry of the tree, as revealed by topological analysis. Later, between 13–15 days and 19–30 days, there was a reelaboration of the dendritic arborization returning to a configuration similar to that found in the newborn. The length of terminal branches was shorter at 19–30 days, while the length of preterminal branches did not change, suggesting that the proliferation of branches at 19–30 days takes place in the intermediate parts of terminal branches. The three‐dimensional distribution of dendrites was analyzed by dividing space into six equal volumes (hexants). This analysis revealed that GG motoneurons have major components of their dendritic tree oriented in the lateral, medial, and dorsal hexants. Further two‐dimensional polar analysis (consisting of eight sectors) revealed a reconfiguration of the tree from birth up to 5–6 days involving resorption of dendrites in the dorsal, dorsomedial, and medial sectors and growth in the lateral sector. Later in development (between 13–15 days and 19–30 days), there was growth in all sectors, but of a greater magnitude in the dorsomedial, medial, and dorsolateral sectors. © 1994 Wiley‐Liss, Inc.
AB - The aim of this study is to describe the postnatal change in dendritic morphology of those motoneurons in the hypoglossal nucleus that innervate the genioglossus muscle. Forty genioglossal (GG) motoneurons from four age groups (1–2, 5–6, 13–15, and 19–30 postnatal days) were labeled by intracellular injection of neurobiotin in an in vitro slice preparation of the rat brainstem and were reconstructed in three‐dimensional space. The number of primary dendrites per GG motoneuron was ∼6 and remained unchanged with age. The development of these motoneurons from birth to 13–15 days was characterized by a simplification of the dendritic tree involving a decrease in the number of terminal endings and dendritic branches. Motoneurons lost their 6th–8th order branches, in parallel with an elongation of their terminal dendritic branches maintaining the same combined dendritic length. The elongation of terminal branches was attributed to both longitudinal growth and the apparent lengthening caused by resorption of distal branches. The elimination of dendritic branches tended to increase the symmetry of the tree, as revealed by topological analysis. Later, between 13–15 days and 19–30 days, there was a reelaboration of the dendritic arborization returning to a configuration similar to that found in the newborn. The length of terminal branches was shorter at 19–30 days, while the length of preterminal branches did not change, suggesting that the proliferation of branches at 19–30 days takes place in the intermediate parts of terminal branches. The three‐dimensional distribution of dendrites was analyzed by dividing space into six equal volumes (hexants). This analysis revealed that GG motoneurons have major components of their dendritic tree oriented in the lateral, medial, and dorsal hexants. Further two‐dimensional polar analysis (consisting of eight sectors) revealed a reconfiguration of the tree from birth up to 5–6 days involving resorption of dendrites in the dorsal, dorsomedial, and medial sectors and growth in the lateral sector. Later in development (between 13–15 days and 19–30 days), there was growth in all sectors, but of a greater magnitude in the dorsomedial, medial, and dorsolateral sectors. © 1994 Wiley‐Liss, Inc.
KW - brainstem
KW - hypoglossal nucleus
KW - respiration
KW - three‐dimensional reconstruction
KW - upper airways
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U2 - 10.1002/cne.903390308
DO - 10.1002/cne.903390308
M3 - Article
C2 - 8132869
AN - SCOPUS:0028054808
SN - 0021-9967
VL - 339
SP - 401
EP - 420
JO - Journal of Comparative Neurology
JF - Journal of Comparative Neurology
IS - 3
ER -