Cytoarchitectonic and quantitative Golgi study of the hedgehog supraoptic nucleus

A cytoarchitectural study was made of the supraoptic nucleus (SON) of the hedgehog with special attention to the quantitative comparison of its main neuronal types. The main purposes were (1) to relate the characteristics of this nucleus in the hedgehog (a primitive mammalian insectivorous brain) with those in the SONs of more evolutionarily advanced species; (2) to identify quantitatively the dendritic fields of the main neuronal types in the hedgehog SON and to study their synaptic connectivity. From a descriptive standpoint, 3 neuronal types were found with respect to the number of dendritic stems arising from the neuronal soma: bipolar neurons (48%), multipolar neurons (45.5%) and monopolar neurons (6.5%). Within the multipolar type 2 subtypes could be distinguished, taking into account the number of dendritic spines: (a) with few spines (93%) and (b) very spiny (7%). These results indicate that the hedgehog SON is similar to that in other species except for the very spiny neurons, the significance of which is discussed. In order to characterise the main types more satisfactorily (bipolar and multipolars with few spines) we undertook a quantitative Golgi study of their dendritic fields. Although the patterns of the dendritic field are similar in both neuronal types, the differences in the location of their connectivity can reflect functional changes and alterations in relation to the synaptic afferences.

Sexual dimorphism in accessory olfactory bulb mitral cells: a quantitative Golgi study

The purpose of the present study was to identify the existence of sexual dimorphism in the dendritic field of accessory olfactory bulb mitral cells in rats and to investigate the effects of male orchidectomy and female androgenization on the day of birth upon this dendritic field. The rapid Golgi method was used to conduct a quantitative study of various characteristics of the dendritic field of accessory olfactory bulb mitral cells. The results indicated greater values for males than females for the following characteristics: (i) somatic area; (ii) degree of branching in the dendritic field; (iii) total dendritic length; and (iv) dendritic density around the neuronal soma. Orchidectomy of males, as well as androgenization of females, on the day of birth inverted these differences.

Neuronal plasticity in the hedgehog supraoptic nucleus during hibernation

The purpose of the present study was to identify processes of plasticity in the receptive field of neurosecretory neurons of the supraoptic nucleus during hibernation in the hedgehog, in order to correlate them with the increased neurosecretory activity observed in this nucleus during this annual period. Using the Rapid Golgi method, a quantitative study was conducted in the receptive field of bipolar and multipolar neurons (the main components of the nucleus). Results indicate a generalized increase in the following characteristics: (1) number of dendritic spines per millimeter along the dendritic shafts; (2) degree of branching in the dendritic field; and (3) dendritic density around the neuronal soma. These data demonstrate modification of the dendritic field in the supraoptic nucleus during hibernation, a change undoubtedly related to functional conditions. Since the observed changes affect structures such as dendritic spines which are directly related to the arrival of neural afferences, the discussion is centered on the types of stimuli which may be responsible for the observed processes.