PHARMACOLOGY

PRESSOR ACTIVITY ::

This activity is determined on the spinal cat A healthy cat weighing between 3.5-4.5 kg is anaesthetized with anaesthetic ether The trachea is exposed and cannulated by a tracheal tube thus providing artificial respiration to the animal The spinal cord is exposed from behind by removing a part of second cervical vertebra An incision is made in the vertebral column The brain is destroyed by passing a probe through the foramen magnum it is then plugged with cotton plug  The temperature of the animal is kept constant by means of a warm copper plate The femoral vein is cannulated by means of a venous cannula Injections are made through the venous cannula 

            The carotid artery is cannulated by means of an arterial cannula and then joined to the manometer for recording arterial BP on the kymograph Initially normal blood pressure is recorded Repeated injections of pituitary extract are made at regular intervals of time A dose of 0.05-1 unit at intervals of thirty min will give suitable rise in BP A fixed volume of normal saline is passed to push the extract towards the heart and to maintain blood volume The doses of the std extract and the test sample are adjusted until they produce an equal rise in blood pressure alternately with varying doses of the test sample till both produce the same rise in BP The activity is expressed in untis /ml 

Antidiuretic activity ::

The experiment is conducted on sixteen male albino rats They should not weigh less than 120 gms and not more than 240 gms The animals must be fasted overnight Warm sterile distilled water is given to them in the doses of 5 ml per 100 gms of body weight intraperitoneally Then they are divided into two group and posterior pituitary extract is injected sc as follows ::

                                                            16 Rats 

                                                                !

                ------------------------------------------------------------------------

                !                                                                                               !

                8                                                                                               8

            0.006 unit                                                                             Equivalent Test 

    Standard in define volume                                                            Sample in same volume 

    The rats are put in metabolic cages so that the urine is collected in a granduated measuring cylinder Following timings are noted :

1.When each group receives water and an injection of posterior pituitary :

2.When urine is first collected in a cylinder for each group and thereafter volume is recorded at intervals of 15 minutes for 3-4 hrs 

    After this period the urine flow stops and observations are discontinued Time in minutes for excretion of half the volume of urine is calculated for each group crossover test is carried out after 24 hrs Those rats which received the std sample previously are now given the test sample and vice versa The experiment is run on similar lines is carried out to minimize errors due to animal variation 

        From the results of two parts of the test mean values are obtained These mean values should be between 95 and 135 min if they are the same for the std and the test sample then both should contain the same units if the times are different then the relative potency can be calculated by comparing with the standard