Synapses on CA1 hippocampal neurons have become a leading model system for understanding CNS synapses and the activity-dependent functional changes that are thought to underlie memory. Structural studies of these synapses have revealed a remarkable diversity of synapse size and diversity in the structure and size of the dendritic spines on which the synapses occur. The function of this diversity is unknown. CNS synapses have other structural specializations, the function of which is also unknown. The general goal of this project is to study the function of single identified synapses and to relate their function to their structure. Critical to this goal is the newly developed method of optical quantal analysis. The method is based on the finding that active synapses can be identified by Ca2+ signals in the spine head using a high-speed confocal microscope. These signals, in conjunction with whole-cell recording, make it possible to characterize an identified synapse by determining the quantal-analysis parameters, p and q. 3D EM reconstructions will be made of the same synapses that are physiologically characterized. Ultrastructural features, such as the size and type of active zone, will be determined. By comparing structure to function, it will be possible to determine whether size is the primary determinant of synaptic strength or whether strong modulatory processes are also at work. Optical quantal analysis will also be used to study the effect of LTP at individual synapses. The data obtained may resolve the controversy regarding the presynaptic/postsynaptic locus of LTP expression. The ability to monitor the function of individual CNS synapses and the ability to relate their function to their structure should have wide ranging applications and wide ranging implications for understanding the synaptic malfunctions that underlie disorders of memory.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS035083-03
Application #
2883694
Study Section
Neurological Sciences Subcommittee 1 (NLS)
Program Officer
Talley, Edmund M
Project Start
1997-03-01
Project End
2001-02-28
Budget Start
1999-03-01
Budget End
2000-02-29
Support Year
3
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Brandeis University
Department
Type
Organized Research Units
DUNS #
616845814
City
Waltham
State
MA
Country
United States
Zip Code
02454
Raghavachari, Sridhar; Lisman, John E (2004) Properties of quantal transmission at CA1 synapses. J Neurophysiol 92:2456-67
Petersen, Jennifer D; Chen, Xiaobing; Vinade, Lucia et al. (2003) Distribution of postsynaptic density (PSD)-95 and Ca2+/calmodulin-dependent protein kinase II at the PSD. J Neurosci 23:11270-8
Conti, Rossella; Lisman, John (2003) The high variance of AMPA receptor- and NMDA receptor-mediated responses at single hippocampal synapses: evidence for multiquantal release. Proc Natl Acad Sci U S A 100:4885-90
Lisman, John (2003) Long-term potentiation: outstanding questions and attempted synthesis. Philos Trans R Soc Lond B Biol Sci 358:829-42
Conti, Rossella; Lisman, John (2002) A large sustained Ca2+ elevation occurs in unstimulated spines during the LTP pairing protocol but does not change synaptic strength. Hippocampus 12:667-79
Otmakhov, Nikolai; Lisman, John E (2002) Postsynaptic application of a cAMP analogue reverses long-term potentiation in hippocampal CA1 pyramidal neurons. J Neurophysiol 87:3018-32
Otmakhova, N A; Otmakhov, N; Mortenson, L H et al. (2000) Inhibition of the cAMP pathway decreases early long-term potentiation at CA1 hippocampal synapses. J Neurosci 20:4446-51
Chen, H X; Otmakhov, N; Lisman, J (1999) Requirements for LTP induction by pairing in hippocampal CA1 pyramidal cells. J Neurophysiol 82:526-32
Otmakhova, N A; Lisman, J E (1999) Dopamine selectively inhibits the direct cortical pathway to the CA1 hippocampal region. J Neurosci 19:1437-45
Otmakhova, N A; Lisman, J E (1998) D1/D5 dopamine receptors inhibit depotentiation at CA1 synapses via cAMP-dependent mechanism. J Neurosci 18:1270-9