Dr. Rob Wykes (ION, UCL, London) implanted two lamp circuits and head fixtures in adult rats on 16-MAY-14. Both the lamp circuits are the rat-sized A3024B-R.
In the first animal, he combined lamp circuit A3024B-R No2.1 with the green-light head fixture A3024HFB-G No2.12. This combination provides 6.4 mW at the tip of the taper. Using the cannula guide, he administered a viral injection of rAAV5/CaMKII-CHR(H134R)-mCherry.
In the second animal, he combined lamp circuit A3024B-R No2.6 with blue-light head fixture A3024HFB-B No2.6. This combination provides 14 mW of blue light at tip of the taper. He administered a viral injection of rAAV5/C1V1-TS-eYFP through the cannula guide.
The head fixture protrudes roughly 10 mm from the skull of the rat. Dr. Wykes enclosed the entire fixture, with the exception of the cannula guide thread, in dental cement. After five weeks, both animals are healthy, active, and the head fixtures remain in place. When the lamps turn on, we see the light clearly through the dental cement.
With the Command Transmitter (A3023CT), he flashes the lamps for 10 ms at 100 Hz. After two weeks, three weeks, and four weeks, there is no significant behavioral change in the rats when the lamp is flashing. Watching videos of the rats with the lamp flashing, it is possible they are curious about the reflection of the light off the walls of the cardboard box in which Dr. Wykes performs his tests.
Today, five weeks after the viral injection, both animals respond to the optical stimulation. They begin to turn in circles after around 15 s and after 60 s they have motor seizures.
UPDATE [21-JUN-14]: Dr. Wykes flashes the lamps for two-minute periods and observes behavior for various pulse lengths and frequencies. With the blue lamp, he observes circling for 2-ms pulses at 10 Hz. With the green lamp, 2-ms pulses at 10 Hz cause no behavioral change, 5-ms pulses cause circling, 10 ms pulses cause no behavioral change, and 20 ms pulses cause circling and seizure. With 10-ms pulses of blue light, 5 Hz causes no behavioral change, 10 Hz causes circling and motor seizure, 20 Hz causes no behavioral change, and 40 Hz causes some circling. With 10-ms pulses at a nominal 10 Hz, but with random displacement of the pulses, there is no behavioral change. The Implantable Lamp (A3024B-R) with a fresh battery can deliver 2-ms pulses at 10 Hz for 100 hours.
