Fluorescent false neurotransmitters (FFNs) are probes which act as novel optical tracers allowing imaging of neurotransmitter release from individual presynaptic terminals in the brain. FFNs have the capability for increasing the understanding of both fundamental and applied neurobiological research including research into neurodegeneration and drug addiction.
Synaptic transmission is the process by which signaling neurotransmitters are released by the pre-synaptic neuron and subsequently bind and activate receptors of the post-synaptic neuron1.
During synaptic transmission, neurotransmitters accumulate in synaptic vesicles and are released by exocytosis from the pre-synaptic neuron. The neurotransmitters subsequently diffuse across the synaptic cleft, bind and activate receptors of the post-synaptic neuron.
Binding then provokes an electrical change in the post-synaptic neuron1. Following release from the pre-synaptic neuron, neurotransmitters are rapidly removed, either by enzymatic destruction or by re-uptake into the pre-synaptic neuron2
Neurotransmitters during synaptic transmission
There are a large number of neurotransmitter types2. Common neurotransmitter types are:
|Amino acids:||Monamines:||Neuropeptides:||Others types:|
There are a variety of key receptors and transporters which play an important role in synaptic transmission and are essential in transporting the various neurotransmitters across biological membranes to various cellular and subcellular locations.
Dopamine active transporter (DAT)
The dopamine active transporter (DAT) is vital in maintaining sufficient dopamine levels in the neuron for release. It also pumps dopamine out of the synapse into the cytosol and is responsible for dopamine re-uptake3
Vesicular monoamine transporter (VMAT)
During synaptic transmission, the vesicular monoamine transporter (VMAT) accumulates neurotransmitters in synaptic vesicles. There are two isoforms of this vesicular membrane protein; VMAT2 and VMAT 14. VMAT2 translocates monoamines such as the neurotransmitter dopamine from the cytosol into synaptic vesicles 5. VMAT1 accumulates monoamines in chromaffin cells of the adrenal medulla 6.
Discovery of fluorescent false neurotransmitters
The fluorescent false neurotransmitters FFN102, FFN202 and FFN511 have been designed to loosely mimic the overall topology and physical properties of monoamine neurotransmitters and have been engineered to have fluorescence properties.
Applications suitable for FFN102, FFN202 and FFN511:
- Measure localization and activity of dopaminergic presynaptic terminals
- Measure pH of secretory vesicles
- Visualize dopamine release from individual presynaptic terminals
Advantages of using fluorescent false neurotransmitters:
- Optically study various aspects of synaptic transmission
- Compatible with GFP tags including Alexa Fluor 488
- Sufficiently bright, photostable and suitable for two-photo fluorescence microscopy
- Suitable for standard fluorescent microscopy
|FFN102 (Mini102)5||Novel, pH-responsive fluorescent false neurotransmitter (FFN). Rodent DAT and VMAT2 substrate. Enables two-photon microscopic imaging of localisation and activity of dopaminergic presynaptic terminals in the striatum of mouse acute brain slice. More selective for dopaminergic synapses than FFN511. Exhibits greater fluorescence emission in neutral than acidic environments allowing optical measurement of synaptic vesicle content release. Sufficiently bright, photostable and suitable for two-photon fluorescence microscopy and standard fluorescent microscopy. Compatible with GFP tags.|
|FFN202 (Mini202)7||Novel, pH-responsive fluorescent false neurotransmitter (FFN). Rodent VMAT1 and VMAT2 substrate. Enables in situ pH measurement of secretory catecholamine vesicles in PC-12 cells. Sufficiently bright, photostable and suitable for two-photon fluorescence microscopy and standard fluorescent microscopy. Compatible with GFP tags.|
|FFN5118||A novel, fluorescent probe for optical imaging and measurement of synaptic activity in the brain. This Fluorescent False Neurotransmitter (FFN) acts as a substrate for the synaptic vesicle monoamine transporter (VMAT2). FFN511 fluoresces sufficiently to provide resolution at the individual synaptic level but at concentrations that do not interfere with normal synaptic function. Inhibits 5HT binding to VMAT2 with an IC50 of 1 μM (comparable to dopamine itself). Compatible with GFP-based tags and other optical probes.|
Recommended resources from our technical team
1. Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 4th edition. New York: Garland Science; 2002.
2. Rang HP, Dale MM, et al. Rang and Dale’s Pharmacology. 6th edition. Elsevier Science; 2007
3. Chotibut T. Dopamine Transporter Loss in 6-OHDA Parkinson's Model Is Unmet by Parallel Reduction in Dopamine Uptake. PLoS One. 7:e52322 (2012). Read More (PubMed: 23300642) »
4. Gros Y. Directed evolution reveals hidden properties of VMAT, a neurotransmitter transporter. J Biol Chem. 12:5076-84. (2010). Read More (PubMed: 20007701) »
5. Rodriguez PC. Fluorescent dopamine tracer resolves individual dopaminergic synapses and their activity in the brain. Proc Natl Acad Sci U S A. 15:870-5 (2013). Read More (PubMed: 23277566) »
6. Sun J. Dopamine D1, D2, D3 receptors, vesicular monoamine transporter type-2 (VMAT2) and dopamine transporter (DAT) densities in aged human brain. PLoS One. 7:e49483 (2012). Read More (PubMed: 23185343 ) »
7. Lee M. Development of pH-responsive fluorescent false neurotransmitters. J Am Chem Soc. 132: 8828-30. (2010). Read More (PubMed: 20540519) »
8. Gubernator NG. Fluorescent false neurotransmitters visualize dopamine release from individual presynaptic terminals. Science. 324:1441-4. (2009). Read More (PubMed: 19423778) »