They serve as a long ways of some japanese words,not some japanese people used it not occasionally, but often.
Look for the following below.
ねぇ(NEe)could considerate as "not" for boys, as they use NEe for じゃない(Janai) which Janai becomes Janee..
なぁ(NAa)could considerate as long way of saying "right" and short for でしょう(Deshou)..
Meanwhile, others often use small A,I,U,E and O for sentences which way they say.