Maturation of otolith-related brainstem neurons in the detection of vertical linear acceleration in rats.
To investigate the critical maturation time of otolith-related neurons in processing vertical orientations, rats (postnatal day 4 to adults) were studied for functional activation of c-fos expression in brainstem neurons by immuno-/hybridization histochemistry. Conscious rats were subjected to sinusoidal linear acceleration along the vertical plane. Labyrinthectomized and/or stationary controls showed only sporadically scattered Fos-labeled neurons in the vestibular nuclei, confirming an otolithic origin of c-fos expression. Functionally activated Fos expression in neurons of the medial and spinal vestibular nuclei and group x were identifiable by P7 and those in group y by P9. A small number of Fos-labeled neurons characterized by small soma size were found in the ventral part of lateral vestibular nucleus by P9. Other vestibular-related areas such as prepostitus hypoglossal nucleus, gigantocellular reticular nucleus and locus coeruleus of normal experimental rats showed functionally activated c-fos expression at P7. Neurons in dorsal medial cell column and beta subnucleus of the inferior olive only showed functionally activated c-fos expression by the second postnatal week. These findings revealed a unique critical maturation time for each of the vestibular-related brainstem areas in the recognition of gravity-related vertical head orientations. By mapping the three-dimensional distribution of Fos-immunoreactive neurons, we found an even distribution of otolith-related neurons within the spinal vestibular nucleus in groups x and y but a clustered distribution in the middle-lateral-ventral part of the medial vestibular nucleus. Taken together, our findings reveal the developmental profile of neuronal subpopulations within the vertical otolith system, thereby providing an anatomical basis for postnatal coding of gravity-related vertical head movements.
Lai
Suk-King
SK
Department of Physiology, Faculty of Medicine, the University of Hong Kong, Sassoon Road, Hong Kong.
Lai
Chun-Hong
CH
Yung
Ken K L
KK
Shum
Daisy K Y
DK
Chan
Ying-Shing
YS
D000054:Acceleration; D000367:Age Factors; D000818:Animals; D001522:Behavior, Animal; D001931:Brain Mapping; D001933:Brain Stem / Q000166:cytology* / Q000254:growth & development; D002452:Cell Count / Q000379:methods; D007758:Ear, Inner / Q000502:physiology; D005260:Female; D018507:Gene Expression Regulation, Developmental; D007150:Immunohistochemistry / Q000379:methods; D017403:In Situ Hybridization / Q000379:methods; D008297:Male; D009474:Neurons / Q000502:physiology*; D016761:Oncogene Proteins v-fos / Q000378:metabolism; D010037:Otolithic Membrane / Q000294:innervation* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012399:Rotation; D013997:Time Factors
D016761:Oncogene Proteins v-fos