The effect of cardiazol convulsions on the distribution and activity of some phosphatases in the area postrema of the rat.

During previous studies on the localization of phosphatases in the central nervous system of the rat it was observed that the area postrema showed intense enzyme activity to a number of important phosphoric acid esters in the acid and alkaline ranges. This structure therefore provided a convenient point upon which to test the effects in situ on some brain enzymes of substances used in neuropsychiatric therapy. Since anatomical information on the area post-rema of the rat was limited, a preparatory study of the medulla was undertaken to establish the normal histology. Cardiazol was the test substance of choice because accurate doses could be administered intravenously and because the subsequent convulsions could be assessed readily according to length and severity. Material and Methods Preparatory anatomical and histological work was carried out on 22 adult albino rats weighing between 200 and 250 g. The methods applied were the ordinary histological staining procedures including various silver impregnation techniques. A histochemical study of the area postrema was made on the frozen-dried brains of 45 adult albino rats. The femoral veins of anaesthetized ratswere exposed and 05 g. of "cardiazol" in a 10% solution in double-distilled water was injected. The convulsions began immediately and the animal was transferred to a chamber into which a small constant flow of oxygen was directed to avoid anoxia. The rats were in convulsions between a half and four hours. Control animals were injected with an equal volume of distilled water and placed in the same atmosphere. An experimental animal and its control were anaesthetized together and both brains were removed rapidly. The cerebellum was then cut through approximately between its anterior two-thirds and posterior third. The caudal block containing the area postrema was immediately dropped into isopentane cooled to below-65° C. in a bath of acetone and CO2 ice. After about two to five minutes the material was transferred to a drying tube made of pyrex glass 15 cm. x 3 cm. provided with a B34 ground socket. The tube was previously filled to the level of about 2.5 cm. with paraffin wax (m.p. 520 C.) and cooled to-78° C. in the acetone and CO, ice bath. The material was placed on this wax bed. The tube was then affixed to the vacuum pump (2.S.50 Edwards) by means of a glass wide-bore adaptor. Between adaptor and pump was interposed an isolation valve and a P205 trap. The tube was …