Sympathomimetic drugs are agents that mimic the responses of epinephrine or stimulation of the sympathetic nervous system. Epinephrine is mainly secreted by adrenal medulla in mammals, whereas norepinephrine is the predominant neurotransmitter present in the peripheral nervous system. In vivo method uses cat spleen. Cats are anasthetized using chloroform. The amount of the noradrenaline present in the blood is estimated by scintillation counter for radioactivity measurement. In vitro methods use cat spleen and rabbit pulmonary artery. The substances that inhibit the actions produced by the sympathomimetic agents or stimulation of sympathetic nervous system are called sympatholytic or adrenergic agents. In vivo methods explain nictitating membrane prolapse in cats. Norepinephrine, epinephrine and isoproterenol have the property of inducing mydriasis, this effect is blocked by α or β blockers. In vitro methods include vas deferens of the rat and splenic strip of the cat. Pithed rats for evaluation of sympthomimetic and sympatholytic activity (in vivo) are discussed. Blood pressure is recorded from the cannulated left carotid artery using a transducer and the arterial pulse is used to trigger a Neilson Instantaneous Ratemeter for the measurement of heart rate. Drugs are administered into the cannulated left femoral vein. To stimulate the thoraco-lumbar region, rod is insulated with an epoxy resin adhesive except the part in close touch with the thorax and lumbar regions of the spinal cord.