Apparatus including an implant is provided, the implant including: a rod-shaped housing, having a distal half and a proximal half, and configured to be injected distally into tissue of a subject a cathode on the distal half of the housing an anchor configured to protrude from the proximal half of the housing, no anchor being configured to protrude from the distal half of the housing an anode and circuitry disposed within the housing, configured to drive a current between the cathode and the anode. Other embodiments are also described.
