Das räumliche Bild des neurosekretorischen Systems der Vögel unter normalen und experimentellen Bedingungen

Summary

• 1. Two techniques are described for the demonstration of neurosecretory material in in toto preparations of the hypothalamus of birds. These permit the study and analysis of the three-dimensional relationships within the hypothalamic neurosecretory system in a cleared and transparent tissue block. The techniques have been applied to the following species: White-crowned Sparrow, Zebra Finch, House Sparrow, chicken, duck and pigeon.

• 2. The first method is adapted from the Victoria Blue technique that was first applied by Braak (1962) for in toto demonstration of the neurosecretory system of fish. The Braak method is based on the Humberstone-Sloper procedure. The required oxidation is effected with performic acid. In addition to the accumulation of Victoria Blue-positive material in the neural lobe there is a second storage site in the palisade layer of the median eminence.

• 3. The second method is one that we have developed for paraldehyde-fuchsin staining in toto, also following performic acid oxidation. With paraldehyde-fuchsin it is possible to demonstrate greater amounts of neurosecretory material than with Victoria Blue. The paraldehyde-fuchsin in toto method is basically useful for the demonstration of avian neurosecretory nuclei. It is possible to demonstrate the three-dimensional relationships of the neurosecretory bundles rostrad to the median eminence and the palisade-like systems of the zona externa. The infundibular portion of the neurosecretory pathway appears loaded with neurosecretory material.

• 4. In frogs (Rana temporaria L.) the paraldehyde-fuchsin method also produces a three-dimensional staining of the subcommissural organ and the Reissner's fiber.

• 5. After photographic documentation in toto, the stained and cleared tissue block can be embedded in paraffin and sectioned serially for a more detailed structural analysis. The totally stained avian hypothalamus can be converted into permanent preparation by embedding in Canada balsam or some other resin.

• 6. The comparison of osmotically stressed (0.3–0.5 M NaCl) specimens of Zonotrichia leucophrys gambelii with non-stressed birds was particularly striking in tissue blocks. The neurosecretory material in the median eminence (palisade layer) of osmotically stressed birds, in contrast to the neural lobe, did not show a detectable decrease.

• 7. The in toto preparations with paraldehyde-fuchsin and Victoria Blue provide a total three-dimensional picture of the neurosecretory system of the avian hypothalamus. They permit a rapid examination of a large number of specimens, and often can eliminate the necessity of subsequent preparation of serial sections and reconstructions. Further possible uses of this technique are discussed.