AB - The brain of adult homeothermic vertebrates exhibits a higher degree of morphological neuroplasticity than previously thought, and this plasticity is especially prominent in birds. In particular, incorporation of new neurons is widespread throughout the adult avian forebrain, and the volumes of specific nuclei vary seasonally in a prominent manner. We review here work on steroid-dependent plasticity in birds, based on two cases: the medial preoptic nucleus (POM) of Japanese quail in relation to male sexual behavior, and nucleus HVC in canaries, which regulates song behavior. In male quail, POM volume changes seasonally, and in castrated subjects testosterone almost doubles POM volume within 2 weeks. Significant volume increases are, however, already observable after 1 day. Steroid receptor coactivator-1 is part of the mechanism mediating these effects. Increases in POM volume reflect changes in cell size or spacing and dendritic branching, but are not associated with an increase in neuron number. In contrast, seasonal changes in HVC volume reflect incorporation of newborn neurons in addition to changes in cell size and spacing. These are induced by treatments with exogenous testosterone or its metabolites. Expression of doublecortin, a microtubule-associated protein, is increased by testosterone in the HVC but not in the adjacent nidopallium, suggesting that neuron production in the subventricular zone, the birthplace of newborn neurons, is not affected. Together, these data illustrate the high degree of plasticity that extends into adulthood and is characteristic of avian brain structures. Many questions still remain concerning the regulation and specific function of this plasticity.
Wow. I wonder now if Decadron may be contributing to my partner's increased irritablity and anger. He gets Decadron as a pre-med infusion every two weeks as part of his chemotherapy treatments. He was also taking Decadron pills for a couple days after chemo, but stopped that (with his oncologist's blessing) a couple of treatments ago. He still gets the black hole appetite though and over the past few weeks has become for angry an intollerant of any mistakes that I or anyone else makes. Does anyone know how long it takes for the Decadron side effects to dissappear?
A case of primary malignant lymphoma involving the splenium of the corpus callosum is reported in a 54-year-old woman presenting with symptoms of increased intracranial pressure. In view of the prominent cerebral edema associated with the intracranial lymphoma, dexamethasone was initiated at a daily dosage of 8 mg by intravenous administration. Computed tomography scans obtained 10 days after admission revealed dramatic regression of the lesion which corresponded with clinical remission. Steroid-induced regression of primary malignant lymphoma of the brain as evidenced by computed tomography is reviewed in the literature, and the role of corticosteroids is discussed.