Electron Microscopic Observation on the Hypothalamohypophyseal System in the Rat

Electron Microscopic Observation on the Hypothalamohypophyseal System in Rats

“…The large vesicles in the median eminence may represent a type of secretory substance or a remnant of large granules which released their content, and the small vesicles may represent the synaptic vesicles containing acetylcholine, the fragments of large granules or vesicles, or a remnant of small dense granules. These possibilities concerning the origin and nature of vesicles were also discussed in our previous paper dealing with the effect of reserpin on the fine structure of the rat median eminence (T. Kobayashi et al, 1968 …”

“…Around the 15th day of birth they also increase in number, but to a much less extent than the large granules mentioned above. Since the small granules closely resemble in size and appearance catecholamines which are present in the median eminence of adult rats (Fuxe, 1964;Matsui and Kobayashi, 1965;Lichtensteiger and Langemann, 1966;Sano, 1966;Kobayashi et al, 1968), and since catecholamines are also demonstrated in the developing rat median eminence by light microscopy (T. Kobayashi et al, 1968, unpublished), the small granules are probably the carriers of catecholamines. It is well known that the monoamines also play a significant role in the hypothalamic regulation of the anterior pituitary function.…”