title: Correlation of non-uniform protein expression with variation in transmitter release probability.
abstract: The strength of synaptic transmission is highly variable between different synapses. The present study examined some factors that may contribute to this variation in the strength of neurotransmission in sympathetic varicosities of the mouse vas deferens. Transmitter release was measured using a focal macropatch electrode placed over pairs of visualised varicosities. By regulating the calcium concentration of the solutions inside the recording electrode and in the bath independently of each other, transmitter release was restricted to one or two surface varicosities at each recording site. Using this technique, transmitter release probability was shown to be highly variable, even between adjacent varicosities on single axon branches. Very little variation was observed in the calcium influx following single impulse nerve stimulation between adjacent Oregon Green BAPTA-1 loaded varicosities. However, the staining intensities of three vesicular proteins, SV2, synaptophysin, and synaptotagmin 1, showed considerable variation between adjacent varicosities on single axon branches. This variation in staining intensity may be partly explained by variation in the density of synaptic vesicles. However, double staining experiments using two vesicular antigens showed some varicosities staining for one vesicular antigen, but not for the second, suggesting that the expression of these release machinery proteins is regulated locally within the varicosities. The results of the present study strengthen suggestions that synaptic strength is at least in part, regulated by variation in the expression of vesicular proteins.
authors.affiliation: School of Biomedical Sciences, University of Queensland, QLD 4072, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Knight
authors.forename: Dwayne L
authors.initials: DL
authors.lastname: Mann
authors.forename: V Margaret
authors.initials: VM
authors.lastname: Jackson
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Trout
authors.forename: Tom C
authors.initials: TC
authors.lastname: Cunnane
authors.forename: Nickolas A
authors.initials: NA
authors.lastname: Lavidis
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D004558:Electric Stimulation / Q000379:methods; D004594:Electrophysiology / Q000379:methods; D007150:Immunohistochemistry / Q000379:methods; D066298:In Vitro Techniques; D007202:Indicators and Reagents / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D046529:Microscopy, Electron, Transmission / Q000379:methods; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011336:Probability; D013569:Synapses / Q000502:physiology / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology* / Q000528:radiation effects; D013572:Synaptic Vesicles / Q000378:metabolism / Q000648:ultrastructure; D016708:Synaptophysin / Q000378:metabolism*; D050863:Synaptotagmin I; D050857:Synaptotagmins; D014649:Vas Deferens / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D002135:Calcium-Binding Proteins; D007202:Indicators and Reagents; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; D016708:Synaptophysin; D050863:Synaptotagmin I; C494311:Syt1 protein, mouse; D050857:Synaptotagmins; D004533:Egtazic Acid; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium