[Neuroscience] A hypothesis (Re: Can a single neuron release multiple neurotransmitters?)

[Entertained by my own EIMC]

I *hypothesize* (or speculate) the existence (or is it already known?) of 
neurons that release one type of transmitter when firing for a relatively 
short time but a different transmitter after a while when firing 
persistently for a relatively long time (or perhaps that after a while of 
persistent firing release 'the last' transmitter at a higher ration to 'the 
first').

Please confirm or debunk as appropriate!

P