[4] While in medical school, he decided that he would make a "terrible clinician", as "he imagined that he would end up seeing only one patient per week, because he would always be too interested in every unknown detail of the case, trying to work out how medicines might act.

"[5] As a result, when required to perform social service as a component of his training in medical school, he chose a research fellowship at the "Instituto Nacional de Cardiología" under Arturo Rosenblueth.

In 1958, he met frequent collaborator, Noble Laureate Bernard Katz, who offered him a position in the Department of Biophysics at University College London.

While there, he spent time developing a technique called microtransplantation, which would allow researchers to study receptors from postmortem diseased human brain tissue in a functional model.

[8] He developed this technique based on earlier work in which he performed the first electrophysiological recording of a frog oocyte, discovering its inherent property of already having neurotransmitter receptors.