The long-term objective of the proposed research is to relate mechanistic information about the basic properties and activity-dependent plasticity of synaptic connections between identified neurons in the vertebrate central nervous system to the operation of the networks in which they are embedded. The experimental model used in these studies is the goldfish Mauthner (M-) cell and its medullary circuits. This neuron mediates an escape response triggered by sensory stimuli from the eighth nerve, and both the electrotonic and chemical synaptic responses triggered by the eighth nerve input exhibit activity-dependent modifications, namely, long- term potentiation (LTP) and depression (LTD). These synaptic responses are also enhanced by the endogenous modulator dopamine. Intradendritic recordings from the M-cell dendrite will be combined with recordings from single afferents and with nerve stimulation, to test specific hypotheses. about the mechanisms of these modifications.
The first aim i s to test the hypothesis that the enhancements of synaptic transmission produced by dopamine and LTP share common intracellular regulatory mechanisms, and that dopamine influences the effectiveness of various tetanizing paradigms. This proposal builds on evidence that dopamine acts through a cAMP-dependent pathway.
The second aim i s to determine the mechanism by which pairing inhibition with a weak tetanus induces LTD. The role of metabotropic glutamate receptors and intracellular Ca++ will be tested. In both aims, the site of the synaptic modification will be determined, with pharmacological methods and postsynaptic injections of compounds that directly interfere with or mimic the effects of the implicated intracellular regulatory pathways. In the third aim, pre- and postsynaptic intracellular recordings will be used to compare the LTP and LTD induced at single connections with modifications in the population responses, and to test the hypothesis that modifications of the strength of single connections depend on their initial efficacy. Particular attention will be paid to the role of silent connections in these phenomena.
The fourth aim i s concerned with short-term plasticity at these synapses and those between the M-axon and identified cells postsynaptic to it in the brainstem, connections which show a marked depression. Specific molecular probes will be injected presynaptically, to determine the molecular determinants of the probability of release and its plasticity. The data will be analyzed statistically, including the techniques of quantal analysis. The mechanisms of synaptic transmission that will be studied in the proposed research are relevant to numerous health-related issues, such as learning and memory and environmental adaptations of nervous system function. Silent synaptic connections potentially provide the substrate for nervous system adaptation, as a function of experience, during development and in response to traumatic injury or stroke.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS015335-25
Application #
6393305
Study Section
Special Emphasis Panel (ZRG1-IFCN-6 (01))
Program Officer
Chen, Daofen
Project Start
1979-09-01
Project End
2003-04-30
Budget Start
2001-05-01
Budget End
2002-04-30
Support Year
25
Fiscal Year
2001
Total Cost
$267,672
Indirect Cost
Name
Albert Einstein College of Medicine
Department
Neurosciences
Type
Schools of Medicine
DUNS #
009095365
City
Bronx
State
NY
Country
United States
Zip Code
10461
Szabo, Theresa M; McCormick, Catherine A; Faber, Donald S (2007) Otolith endorgan input to the Mauthner neuron in the goldfish. J Comp Neurol 505:511-25
Szabo, T M; Weiss, S A; Faber, D S et al. (2006) Representation of auditory signals in the M-cell: role of electrical synapses. J Neurophysiol 95:2617-29
Smith, Mackenzie; Pereda, Alberto E (2003) Chemical synaptic activity modulates nearby electrical synapses. Proc Natl Acad Sci U S A 100:4849-54
Preuss, Thomas; Faber, Donald S (2003) Central cellular mechanisms underlying temperature-dependent changes in the goldfish startle-escape behavior. J Neurosci 23:5617-26
Kumar, S S; Faber, D S (1999) Plasticity of first-order sensory synapses: interactions between homosynaptic long-term potentiation and heterosynaptically evoked dopaminergic potentiation. J Neurosci 19:1620-35
Pereda, A E; Bell, T D; Chang, B H et al. (1998) Ca2+/calmodulin-dependent kinase II mediates simultaneous enhancement of gap-junctional conductance and glutamatergic transmission. Proc Natl Acad Sci U S A 95:13272-7
Bell, T D; Pereda, A E; Faber, D S (1997) Nitric oxide synthase distribution in the goldfish Mauthner cell. Neurosci Lett 226:187-90
Pereda, A E; Faber, D S (1996) Activity-dependent short-term enhancement of intercellular coupling. J Neurosci 16:983-92
Silva, A; Kumar, S; Pereda, A et al. (1995) Regulation of synaptic strength at mixed synapses: effects of dopamine receptor blockade and protein kinase C activation. Neuropharmacology 34:1559-65
Pereda, A E; Bell, T D; Faber, D S (1995) Retrograde synaptic communication via gap junctions coupling auditory afferents to the Mauthner cell. J Neurosci 15:5943-55

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