We constructed a portable system for acquisition of the electrical activity of a brain. We succeeded in acquiring the electroencephalogram and nociceptive evoked potentials in the somatosensory S1HL and the anterior cingulate Cg cortexes in the right hemisphere in rats. The key features of the system consist of the following: high sensitivity; absence of any filters; high-resolution measurement; this results in the near absense of data loss while acquiring the real time brain electric activity. The problem to get rid of the intense electromagnetic pollution was solved by making use of a multilayer shielding of the analogue part of the system and by using an autonomous direct current source to feed the whole system. This system is portable and works with a notebook computer. The solutions we have utilised while setting up this system are pioneering and allow us to deal with a wide range of problems of electrophysiology.