Local anaesthesia induces immediate receptive field changes in nucleus gracilis and cortex.

The reorganization of receptive fields of nucleus gracilis neurones after local anaesthesia, and its relationship to the reorganization of cortical maps were studied in the rat. Cutaneous stimulation was performed using electronically gated air jets. Single unit recordings were obtained in gracilis nucleus and somatosensory cortex. Temporary anaesthesia was induced with lidocaine (2%, 5-15 microliters s.c.), which blocked the responses in < 2 min and provoked the simultaneous appearance of new overlapping receptive fields in gracilis and cortical neurones in 2-30 min. The present results suggest that the early reorganization of somatosensory cortical maps after temporary anaesthesia may be partly due to the emergence of new receptive fields in nucleus gracilis neurones.