The dipolar relaxation time (T1D) is related to motion restricted molecules and could be used to assess myelin molecular dynamics associated with physiopathology processes. T1D was measured with the inhomogeneous magnetization transfer (ihMT). T1D maps were obtained from in-vivo mouse brain and from ex-vivo rat spinal cord at different temperatures. T1D was approximately 5ms in brain and 1.8ms in muscle. T1D in spinal cord was doubled from 26°C to 37°C, reflecting changes in molecular dynamics caused by the temperature rise. Measuring T1D in-vivo could give information about the myelin membrane structure altered in neurological disorders.