1992 年 4 巻 1 号 p. 71-79
The distribution of noradrenergic fibers and their synaptic inputs to neurosecretory neurons in the paraventricular (PVN) and supraoptic (SON) nuclei of the rat hypothalamus were investigated by a method of pre-embedding peroxidase antiperoxidase using antiserum against noradrenalin (NA) itself at the light and electron microscopic level. Many NA-like immunoreactive (NA-LI) fibers and terminals were distributed in both the parvocellular and magnocellular parts of the PVN and in the SON where many neurosecretory neurons were located. Ultrastructural observation revealed that NA-LI axon terminals form synapses with both the parvocellular and magnocellular neurosecretory neurons and their processes in the PVN and SON. NA-like immunoreactivity was mainly observed in dense granular vesicles (70-90 nm in diameter) but not in small clear synaptic vesicles (30-50 nm in diameter) in the NA-LI axon terminals. These findings provide morphological evidence for direct synaptic influence of noradrenergic elements on the secretory activity or other functions of neurosecretory neurons in the rat hypothalamic PVN and SON.
