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Immunoperoxidase histochemical investigations on pig hypophysis show that CRF immunoreactive nerve terminals are distributed around the blood vessels in the posterior lobe, particularly in its proximal part adjacent to the intermediate lobe. CRF immunoreactive nerve fibers are also seen in the intermediate lobe. The distribution of the CRF-containing nerve in the posterior lobe was found to be similar to that of the vasopressin-containing nerve terminals. The functional significance of the presence of CRF-containing nerve fibers representing a new component of the hypothalamo-hypophyseal neurosecretory system is discussed.

The distribution of vasopressin-, oxytocin- and LHRH-containing nerve fibers in the pineal organ of the dog was demonstrated by use of the peroxidase-antiperoxidase immunohistochemical technique. These neuropeptide-containing fibers penetrated through the pineal stalk from the brain, mainly from the posterior commissural region, into the pineal organ. The vasopressin fibers were the most prominent in number, oxytocin fibers and LHRH fibers were the least. Most of these fibers were found in the proximal part of the pineal organ, but some of them were also observed in the distal part. These peptidergic fibers were distributed not only in the perivascular spaces but among the parenchymal cells.

Serotonin neurons in newborn mouse and rat brainstem cultures were studied by peroxidase-antiperoxidase immunohistochemistry using a serotonin antibody. The intensity of the immunohistochemical reaction in the neuronal somata decreased gradually with time and was hardly detectable after one month of culturing. On the other hand, the immunoreactivity of the processes noted at the early stages later on became more intense and covered the full extent of the fibers. From the early stages of the cultures, the axon of each serotonin neuron formed not only a network by branching, but also a true anastomosis with the axonal networks of the other serotonin neurons.

The otic and pterygopalatine ganglia and, as controls, the superior cervical ganglia of the dog were studied by the histochemical fluorescence methed of FALCK and HILLARP.Most nerve cells of the superior cervical ganglion contained monoamine specific fluorescent granules, and numerous monoaminergic terminals occurred among and around the neurons. There were, however, found neither adrenergic neurons nor adrenergic teminals in both the otic and the pterygopalatine ganglia in normal and even in nialamide-treated animals. A yellow-brown fluorescence of unknown nature, which did not disappear after the administration of reserpine as well as after cervical and upper thoracic sympathetic ganglionectomy, was found in the perikarya of nerve cells in these ganglia.The findings obtained suggest that there is no adrenergic neuron in both the otic and the pterygopalatine ganglia, and that sympathetic fibers originating from the sympathetic trunk do not make neuron exchange in the two ganglia.

The dog retina was investigated with the fluorescence microscopical method for catecholamines introduced by FALCK and his co-workers (1962).Dopamine was administered intravenously, intraventricularly and intravitreously. Both intravenous and intraventricular dopamine significantly increased the number of the fluorescent amacrine cells. With the intravitreous administration almost all amacrine cells became fluorescent. These facts indicate that at least a large part of the amacrine cells is dopaminergic by nature. On the other hand, no significant changes were recognized in the fluorescent elements other than those in the amacrine cells.Dopamine intravitreously administered entered into the stratum cerebrale, but not beyond this. It is supposed that there is a certain barrier between the stratum cerebrale and neuroepitheliale.

The axoplasmic transport of catecholamines in sympathetic neurons was examined with the formaldehyde fluorescence method for biogenic amines. The whole course of canine colonic nerves, from the caudal mesenteric ganglion to the terminals in the colonic wall, as well as the sciatic nerve was used. Besides normal animals, various experimental conditions caused by axotomy, ligation, reserpinization, and their combinations were studied. The proximal cut end of the colonic nerve was also observed electron microscopically in comparison with the normal nerve.1. Most nerve cells in normal caudal mesenteric ganglia possessed catecholamine specific fluorescence. Some fluorescent nerve fibers passed by them while others terminated on them. Every part of the colonic nerve weakly fluoresced. In the colonic wall the fluorescent nerve fibers entered the submucosal nerve plexus.2. After administration of reserpine the entire length of the colonic nerve became non-fluorescent in 6hrs. In 24hrs the ganglion cells first became weakly fluorescent, in 48hrs the fluorescence was somewhat intensified and in 96hrs it returned to normal and a weak fluorescence reappeared in the terminals in the colonic wall.3. After section at the branching site of the colonic nerve and at the root of all other nerves arising from the caudal mesenteric ganglion, fluorescent nerve cells in the ganglion decreased in number with time, whereas the fluorescent materials accumulated in the proximal cut end reaching a maximum 7 days after section and then decreasing. The fluorescence in the distal cut end and in the terminals in the colonic wall disappeared after 4 days.4. One to 2 days after double ligations of the colonic nerve, the fluorescent material accumulated more markedly to the proximal end rather than distal end of the nerve segment between the ligations.5. When reserpine is given after axotomy the fluorescence in the proximal cut end of the nerve almost completely disappeared in 24hrs. When the nerve is sectioned after pretreatment with reserpine, the fluorescence in the proximal cut end disappeared as late as 5 days after axotomy.6. Fluorescent nerve fibers in the sciatic nerve lost their fluorescence 7 days after resection of the lumbar sympathetic trunk.7. In the proximal cut end of the colonic nerve, a number of large granular vesicles with a diameter of 1, 100-1, 500A were observed electron microscopically. Even with the use of KMnO4 fixation small granular vesicles (500A diameter) were never detected. The large granular vesicles were also found sparsely in normal axons of the colonic nerve.From these findings we conclude that the fluorescent materials, representing catecholamines, are synthesized within the cell bodies of the sympathetic gangilon cells, transported distally towards the terminals, by means of an axoplasmic flow. Electron microscopical findings suggest that at least most of the catecholamines may be contained in large granular vesicles to be transported to the periphery. The relation of this type of vesicles to the small granular vesicles in the nerve terminals is unknown.