Norepinephrine neurons (NE)
In the absence of DA β-hydroxylase, a norepinephrine neuron becomes a dopamine neuron.
A dysregulation of norepinephrine is associated with depression.
Extra info: According to the monoamine hypothesis, depression is caused by a dysregulation of norephinephrine and serotonin.
Noradrenergic α2 auto-receptors are present on the presynaptic axon providing a quick negative feedback loop in the synapse.
Extra info: This sort of auto-receptor provides the synapse with a quick mechanism for inhibiting futher release of norepinephrine into the synapse.
α2 auto-receptors decrease post-synaptic α1 neurotransmission but NOT β1- and 2- neurotransmission.
Extra info: The α2-receptors decrease the transmission of norepinephrine, which freely interacts with both α and β-receptors.