c-Fos mRNA and the related Fos-protein are rapidly induced by physiological stimuli and can be used as molecular markers of neural activation and plasticity, We have recently shown that unilateral labyrinthectomy (UL) produced in rats an asymmetric increase of the c-fos and Fos-protein expression not only in the vestibular nuclei, the inferior olive. the cerebellar cortex and the caudate-putamen. as reported in previous studies. but also in the locus coeruleus (LC)-complex. particularly of the intact side, whose neurons integrate labyrinthine signals and are apparently involved in the plastic changes which are at the basis of vestibular compensation. The putative noradrenergic nature of the Fos-positive LC-complex neurons observed after UL was studied by combining Fos-protein immunocytochemistry with the immunocytochemical detection of tyrosine hydroxylase (TH), one of the synthetizing enzymes of noradrenaline (NA). It was then possible to verify that Fos-positive LC-complex neurons were presumably noradrenergic in nature, as they could be double labeled with the Fos/TH technique. This finding appeared 3h after the lesion. decreased 6 h after UL and disappeared after 24 h, when partial compensation of the vestibular syndrome had occurred, Thus, UL results in asymmetric functional activation in the LC-complex of noradrenergic neurons. This observation was attributed to the fact that asymmetric stimulation of labyrinth receptors gives rise to asymmetric changes in firing rate of LC neurons. Since these neurons send noradrenergic afferents to several target structures such as the vestibular nuclei, the inferior olive, the cerebellar cortex and the caudate-putamen, we postulated that the asymmetric,activation of the noradrenergic LC system after in could increase the Fos-protein expression in the above mentioned target structures. thus representing a key factor in determining the plastic changes, which are at the basis of vestibular compensation.
|Autori interni:||D'ASCANIO, PAOLA|
|Autori:||d'Ascanio P; Arrighi P; Pompeiano O|
|Titolo:||The locus coeruleus and Fos-protein expression in vestibular compensation|
|Anno del prodotto:||1998|
|Appare nelle tipologie:||1.1 Articolo in rivista|