Cystyl aminopeptidase activity in the plasma, viscera and brain of the snake Bothrops jararaca

Hypothalamic activity during altered salt and water balance in the snake Bothrops jararaca

The effects of water and salt overload on the activities of the supraoptic and paraventricular nuclei and the adjacent periventricular zone of the hypothalamus of the snake Bothrops jararaca were investigated by measurements of Fos-like immunoreactivity (Fos-ir). Both water and salt overload resulted in changes in body mass, plasma osmolality, and plasma concentrations of sodium, potassium, and chloride. Hyper-osmolality increased Fos immunoreactivity in the rostral supraoptic nucleus (SON), the paraventricular nucleus (PVN), and adjacent periventricular areas. Both hyper- and hypo-osmolality increased Fos immunoreactivity in the intermediate SON, but not in other areas of the hypothalamus. Immunostaining was abundant in cerebrospinal fluid (CSF)-contacting tanycyte-like cells in the ependymal layer of the third ventricle. These data highlight some features of regional distribution of Fos immunoreactivity that are consistent with vasotocin functioning as a hormone, and support the role of hypothalamic structures in the response to disruption of salt and water balance in this snake.

Absence of oxytocin in the central nervous system of the snake Bothrops jararaca

We used four complementary techniques to investigate the presence of oxytocin peptide in the hypophysis and brain of the snake Bothrops jararaca. A high-pressure liquid chromatographic analysis failed to show oxytocin in extracts of hypophysial and brain tissues but provided estimative values of the amounts of vasotocin (12 ng/mg hypophysis and 0.5 ng/mg brain) and mesotocin (500 pg/mg hypophysis and 8 pg/mg brain). Western blots with a polyclonal anti-oxytocin antibody failed to detect oxytocin in both tissues but detected compounds with higher molecular weight than oxytocin, as well as a relatively weak cross-reactivity with mesotocin. The reverse transcription-polymerase chain reaction analysis failed to detect the expression of oxytocin gene transcript, but detected a transcript related to the mesotocin-neurophysin precursor in both tissues. Immunohistochemistry with the same anti-oxytocin antibody detected strong staining in the neurohypophysis and in few fibers in the inner zone of the median eminence, which was not abolished by pre-adsorption of this antibody with oxytocin, vasopressin, vasotocin or mesotocin and might not be attributed to oxytocin. In conclusion, our data demonstrate the absence of oxytocin in the central nervous system of the snake B. jararaca and underline the pitfalls that can result from the use of a single technique to investigate the presence of peptides in tissues.