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Nanoplasmonic metamaterials are an exciting new class of engineered media that promise a range of important applications, such as subwavelength focusing, cloaking and slowing/ stopping of light. At optical frequencies, using gain to overcome potentially not insignificant losses has recently emerged as a viable solution to ultralow-loss operation that may lead to nextgeneration active metamaterials. Here we report on extensive computational simulations based on an ab initio Maxwell-Bloch Langevin approach that grasps the coherent and quantum noise properties of the gain medium and thus amplified spontaneous emission medium together with dynamic nanoplasmonic coherence in metamaterials. For the generic example of an optically pumped nano-fishnet metamaterial with an embedded laser dye (four-level) medium exhibiting a negative refractive index we demonstrate the transition from loss compensation to amplification and to nanolasing. We report ultrafast relaxation oscillations of the bright negative-index mode with frequencies just below the THz regime.