Isoprenaline on Parkinsonian Tremor

The development of pharmacological substances, capable of exerting powerful effects at known sites in the nervous system, has provided a new versatile tool for clinical research. No longer is it necessary to destroy a part of the nervous system in order to study what effect it may have upon a phenomenon; the activity of that part may be held in abeyance by the use of pharmacological blocking agents. Likewise, stimulation no longer always demands the application of electrodes; drugs acting at a specific site provide a more elegant experiment. But the supreme advantage is that these methods can be applied to man, thus eliminating the many pitfalls which arise when human problems are studied in other species. The aggravation of Parkinsonian tremor which occurs when a patient becomes emotionally upset has long been attributed to the release of adrenaline, and Barcroft, Peterson, and Schwab (1952) have shown that the infusion of adrenaline into patients suffering from Parkinsonism increases their tremor. These workers had not, however, the means at their disposal of ascertaining the site of action of the adrenaline. There is evidence that adrenaline can act at several sites in the nervous system. Thus, Marazzi (1960) has shown that adrenaline may cause inhibition at cortical synapses, and McLennan (1961) found that catechol amines, when applied to the exposed spinal cord of the cat, inhibit the knee jerk. The present study was carried out to ascertain the site at which catechol amines act in aggravating Parkinsonian tremor.