Dale's Law

has been rescinded

• Dale's Law is commonly paraphrased as a neuron is either excitatory or inhibitory.
• I think the actual law is that a neuron releases only one type of neurotransmitter.
• It's not clear that Dale meant this as a law or merely as a hypothesis.
• It seems that it's not the case. Synapses often release multiple neurotransmitters.
• It seems that the type of pre and post synaptic neuron matters so that neuron A can excite neuron B (of type B') and inhibit neuron C (of type C').
• Still it's important to note the constraint.
• If we're trying to be biologically accurate, we probably should specify our inhibitory excitatory constraints, and map that to biological evidence.
• If we're not particularly concerned with biology, we should probably state that.
• It should also be noted that a stronger constraint is that synapses do not usually go from being inhibitory to excitatory or vice-versa. As this is a long term change, there may be rare counter examples.