Unformatted text preview: Synaptic Plasticity II:
Learning and Memory
Dr. McKemy 92408 Hippocampus: area critical for memory storage and retrieval. Damage to this region can prevent the formation of certain types of new memories. Slice preparations have been used most extensively to study memory in the rodent brain. Longterm potentiation: LTP Longlasting increased synaptic strength. Longterm depression: LTD Longlasting decrease in synaptic strength. The rodent hippocampus Longterm potentiation of Schaffer collateralCA1 synapses Longterm potentiation of Schaffer collateralCA1 synapses Longterm potentiation can be longtasting LTP is "statedependent". Postsynaptic membrane potentials determines if LTP will occur. The postsynaptic depolarization must occur within 100 msec of presynaptic neurotransmitter release. Pairing presynaptic and postsynaptic activity causes LTP LTP is also "input specific". If LTP is induced in one synapse, this does not mean that it will occur in other synapses of the neuron. Associativity involves the simultaneous "association" if two inputs. Strongactivation paired with weak activation. LTP also is "associative". LTP at a CA1 pyramidal neuron receiving inputs from two independent pathways The NMDA receptor can only open during depolarization of the post synaptic neuron. Molecular mechanisms of LTP NMDA vs AMPA ionotropic glutamate receptors Ca2+ entry through NMDA receptors produces LTP. Activation of NMDA receptors evokes an increase in intracellular Ca2+. Can be blocked by buffering intracellular Ca2+. Increased Ca2+ starts a phosphorylation cascade. CamKII and PKC. Final events lead to an increase in the # of AMPA receptors in the postsynaptic terminal. Signaling mechanisms underlying LTP Increased glutamate sensitivity after LTP induction. Also, activates "silent synapses". Addition of postsynaptic AMPA receptors during LTP Silent Synapses Silent Synapses Mechanisms responsible for changes in synaptic transmission during LTP Role of protein synthesis for maintaining LTP Creation of new synapses may also occur during LTP. Figure shows new spines 1hr. after LTP induction. CA1 pyramida l neuron Mechanisms responsible for changes in synaptic transmission during LTP LTP is evoked by brief, high frequency stimulation. 100 Hz for 110 sec. Longterm depression (LTD) will occur with low frequency, long period stimulation. 1 Hz for 1015 min. Longterm synaptic depression in the hippocampus Both LTD and LTP require NMDA receptors and Ca2+ entry into the postsynaptic cell. Small, slow rise in Ca2+ LTD. Fast, large rise in Ca2+ LTP. Longterm synaptic depression in the hippocampus Longterm synaptic depression in the cerebellum Longterm synaptic depression in the cerebellum ...
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- Fall '08
- Neurobiology, Chemical synapse, Long-term potentiation, LTP, NMDA receptor