What are the practical advantages of noradrenaline?
Another practical advantage is the long half-life of [3H] which allows it to be stored for extended periods of time. In this experiment, we will utilize the reuptake mechanism of noradrenaline to fill vesicles with the radio-isotope [3H]-noradrenaline and then examine the effect of receptor agonists and antagonists on the [3H]- noradrenaline release. This investigation contains three parts. First, we will observe the effect of stimulation and inhibition of the pre-synaptic alpha-2 receptor during electrically evoked synaptic transmission using clonidine and yohimbine, respectively. Next, we will examine the effect of stimulation and inhibition on the post-synaptic alpha-1 receptor using phenylephrine and prazosin, respectively. In the last portion, we will use desipramine to observe the effect of reuptake inhibitors and tyramine (which displaces noradrenaline from vesicles) on noradrenaline release during synaptic transmission. We hypothesize that stimulation of the pre-synaptic a2-receptor will inhibit further [3H]-noradrenaline release from the pre-synaptic neuron, while inhibition of this receptor will encourage neurotransmitter release. We predict that stimulation of the post-synaptic a1-receptor will increase [3H] release, whereas inhibition of the receptor will decrease neurotransmitter release.
Inhibitors and drugs that displace noradrenaline from its vesicle should both increase the release of [3H]. Ultimately, this experiment will allow us to gain a better understanding of the mechanisms of neurotransmitter release within the brain.