[Immunocytochemical study of the hypophyseal neural lobe of Natrix maura in dehydration].

The influence of the dehydration treatment on the hypophysial neural lobe of the water snake Natrix maura, has been investigated. Whereas control animals stayed in fresh water, experimental snakes were immersed in a hypertonic solution of sodium chloride (35%) for 48 h. All specimens were fixed by vascular perfusion with Bouin fluid and the pituitaries embedded in paraffin. The sections were stained through histochemical procedures and immunocytochemistry by means of antisera against bovine neurophysins, vasotocin and mesotocin. The intensity of the immunoreaction was measured by microdensitometry. The osmotic stress significantly decreases the amount of stainable neurosecretory material in the neural lobe as well as the immunoreactivity to antineurophysin and antivasotocin sera. Contrariwise, there is no clear decrease in the immunoreactivity to antimesotocin serum. These results suggest that the osmotic stress in Natrix maura elicited an increase in the release of vasotocin.