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The influence of osmotic stimulation on the density of beta-adrenoceptor binding sites in the rat supraoptic nucleus (SON) was studied by quantitative autoradiography using 125I-cyanopindolol (ICYP). Increased density of beta-adrenoceptor binding sites was observed in osmotically stimulated rats and also after the suppression of neuronal activation by rehydration of animals. This was mainly due to a significant increase in the concentration of beta 2 binding sites. The overexpression of beta-adrenoceptors occurred concomitantly with nuclear expansion in SON astrocytes. Moreover, the higher concentration of beta-adrenoceptors observed in the ventral portion of the SON largely coincided with the area that showed intense GFAP-immunostaining. These results provide indirect evidence of an astrocytic location of beta-adrenoceptors and also of beta-adrenergic mediation in the structural and functional changes of SON astrocytes.

The morphology and degree of maturation of intrafissural colony-forming ectopic granule cells (EGCs) were investigated in the cerebella of normal adult rats. These EGCs exhibit a notable degree of morphological maturity, with 2-5 short dendrites radiating from a globular soma, typical dendritic claw-like terminals and descending axons. The EGCs receive the afferent input of mossy fiber terminals and their axons also establish homologous synapses with the postsynaptic dendritic spines of the Purkinje cells. Although these EGCs exhibit the typical morphology of mature granule cells, the morphometric analysis shows, however, a significant reduction in the number of dendrites (mean 3.30 +/- 0.60) and 'claws' (mean 3.66 +/- 0.12) in the EGCs with respect to the controls (mean 3.85 +/- 0.73 and 4.53 +/- 0.13, respectively). These differences may be indicative of a slight numerical mismatching between EGCs and afferent mossy fibers, which limit the input that the ectopic neurons receive. The karyometric study also showed that the average nuclear area in EGCs was significantly smaller (mean 19.38 +/- 0.24 micron2) than in controls (mean 21.88 +/- 0.24 micron2), suggesting a positive correlation between nuclear size and the number of postsynaptic dendritic terminals available in the granule cells. The influence of some morphogenetic factors on the degree of maturity attained by these ectopic neurons is discussed, particularly the interactions of mossy fibers and astrocytes with maturing EGCs.

Single-teased fibers stained with the ferric ion-ferrocyanide method 14 allowed us to study axonal remodeling in the lead-induced demyelinating neuropathy of the rat. Our findings, in agreement with recent physiological data, pointed to a transitory reorganization of the demyelinated axons to maintain impulse conduction until remyelination and formation of new cytochemically normal nodes had restored a secure saltatory conduction.

The morphological types of isolated ectopic granule cells (EGCs) were examined with Golgi-Rio Hortega staining in the cerebellar molecular layer of adult normal rats. The EGCs showed a significant reduction in the number of dendrites (mean 2.42 +/- 0.07) with respect to the controls (mean 3.97 +/- 0.09), and they usually exhibited poorly developed dendritic terminals. The karyometric analysis on semithin sections indicated that the average nuclear area in EGCs was significantly smaller (16.62 +/- 0.20 micron 2) than in normally positioned granule cells (21.08 +/- 0.24 micron 2).