Can 行くな change to 行くぬ with the same meaning "Don't go"?
From your comment:
I see that な when combined with a dictionary form of a verb produces the negative imperative. And ぬ can be replaced with ない. So can な replaced with ぬ with the same meaning?
First of all, no. The な is a particle (助詞). ぬ and ない are auxiliaries (助動詞).
The negative imperative な is attached to the attributive form (連体形) of a verb:
行く+な → 行くな "Don't go!"
The negative auxiliaries ぬ and ない are attached to the imperfective form (未然形) of a verb. The 未然形 of 行く is 行か, so:
行く+ない → 行かない / 行く+ぬ → 行かぬ "don't go"
In modern Japanese, the auxiliaries ない and ぬ don't have the imperative form (命令形).
(In classical Japanese, the terminal form of ぬ is ず, and its imperative form is ざれ.)