Found this
Nikon D300 Review: 18. Photographic tests: Digital Photography Review gives a comparison chart of ISO for the D300. After a very brief Google on the subject there appears to be some debate going on about the noise with some people comenting on it being 'grainy' but nothing as to the cause.
Judging from the shot I doubt that the camera would be doing any NR processing on the shot though this also appears to be under debate as to whether the camera does anything with the RAW image no one seems to know for sure.