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Flashcards in 4: normal aging 2 Deck (20):

LTP induction follows __ rule? requires? dependent on?

Hebb rule. coincident presynaptic and post synpatic activity. NMDA receptor dependent


what is critical for LTP induction?

NMDA receptor. block = eliminate induction


____ entry through NMDA-R critical for?

calcium entry. induction + expression of synaptic changes. large changes in intracellular Ca induce LTP


at certain synapses, LTP induction can occur without? requires?

participation of NMDA neurotransmission. uses voltage dependent calcium channels (high threshold, L-type)


Ca is both ___ and ____

an ion and signaling molecule


large post synpatic increase in Ca triggers an increased in _________ via (3)?

post synaptic responsiveness: increase in AMPA receptors post synpatically, increased in neurotransmitter release presynaptically, increase in synaptic contacts


medium term expression vs. long term maintenance of LTP?

expression: local signaling mechanisms, local protein synthesis. maintenance: nuclear involvement via genomic translation


need opposing mechanism for LTP?

a mechanism for synaptic enhancement like LTP requires an opposing mechanism to prevent synaptic saturation


LTD induced by ___? 2 ways?

stimulation patterns that violate Hebb's principal: presynpatic activity without post synaptic activity. post synaptic activity without presynaptic activity


LTD: how to stimulate presynaptic activity without post?

weak, low freq repetitive stimulation of presynaptic inputs. temporally mismatched and uncorrelated activation of different weak and strong presynp. inputs


LTD: how to stimulate postsynp activity without pre?

repetitive low frequency depolarization of postsynp. cell. temporally mismatched/uncorrelated activation of weak presynaptic inputs and depolarization of post synaptic cell


3 types of LTD

homosynaptic. hetersynaptic. associative


homosynaptic LTD?

low freq input from presynp, neuron with no response from post synp cell


heterosynaptic LTD

strongly activate one pathway = induces LTP, depol. post synp cell while at the same time expressively not activate another pathway = you get heterosynaptic LTD in non activated pathway


mechanism of LTD

calcium dependent synaptic depression: low concentrations of calcium entry in post synp cell elicit changes which oppose synp. enhancement


LTD: evoked by? 3 pre/post synp changes?

evoked by both NMDA-R and voltage-dependent ca channel activation. decrease in postsynp AMPAR, presynp release of glut, and synaptic contacts


how does aging affect LTP?

stimulus threshold for induction higher. faster rate of decay (maintenance)


how does aging affect VDCC-dependent LTP?

stimulus threshold LOWER for induction (because of ca homeostasis changes)


how does aging affect NMDA dependent LTP?

induction: stimulus threshold higher


how does aging affect LTD?

enhanced induction of LTD, lowered threshold