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Long-term potentiation of transmission at neocortical synapses in slices of rat sensorimotor cortex and the involvement of NMDA receptors

Murphy, Kerry Peter Sean James; (1991) Long-term potentiation of transmission at neocortical synapses in slices of rat sensorimotor cortex and the involvement of NMDA receptors. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

1. Long-term potentiation (LTP) is an enduring activity-dependent increase in synaptic efficacy which has been considered as a neural substrate for learning and memory. 2. LTP was induced in 22% of postsynaptic potentials (p.s.p.s) and 87% of field potentials evoked by stimulation of the subcortical white matter and recorded in layers III, V & VI of slices of adult rat sensorimotor cortex. Conditioning paradigms used were either high frequency stimulation of an afferent pathway or the repetitive pairing of an afferent volley with a postsynaptic injection of depolarizing current. Intracellularly recorded LTP was found to be input specific, homosynaptic and associative. 3. D-2-amino-5-phosphonopentanoic acid (AP5) was used to assess the involvement of N-methyl-D-aspartate (NMDA) receptors in neurotransmission and in the induction and expression of LTP in the neocortex. The majority of p.s.p.s (89%) and field potentials (80%) were mediated in part by NMDA receptors. A non-NMDA receptor mediated component always preceded a NMDA receptor mediated one. 4. AP5 blocked the induction of LTP in field potentials recorded in 5 out of 7 slices; following washout of AP5, a second, identical set of conditioning stimuli induced LTP. 5. AP5 applied 15-20 minutes after the induction of LTP, reduced the magnitude of potentiated field potentials in 13 out of 13 slices and 4 out of 4 potentiated p.s.p.s. A potentiated non-NMDA receptor mediated component preceded a potentiated NMDA receptor mediated one. 6. In most cases, the onset latency of the potentiated component of p.s.p.s was delayed by ~2ms after the onset of synaptic activity. This delay was not voltage-dependent. LTP appeared to be a property of intrinsic neocortical connections but not of the fastest conducting afferents, possibly arising from outside the neocortex.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Long-term potentiation of transmission at neocortical synapses in slices of rat sensorimotor cortex and the involvement of NMDA receptors
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Biological sciences; Long-term potentiation
URI: https://discovery.ucl.ac.uk/id/eprint/10122318
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