This is due to the strong action of NMDA channel which keep this activity alive before afterhyperpolarization.
The channels for the AMPA current are also activated in a similar fashion as NMDA channels with a periodic simulation of a cluster of synapses .
Besides this, calcium signals invoked through NMDA channels are consider to be the key player behind LTP and LTD, a neurocellular basis of learning and memory formed in hippocampus [19,32].
Some of these processes for which a direct regulatory role for magnesium has been described include energy metabolism, vascular reactivity and membrane stability, RNA aggregation, protein synthesis and DNA replication, activity of excitatory amino acid channels including NMDA channel binding, glutamate release, calcium influx, lipid peroxidation and generation of free radicals, vasospasms and rupture of blood vessels, decreased cerebral blood and activity of specific endogenous opioid peptides.
[28.] Golding EM, Vink R: Efficacy of competitive versus noncompetitive blockade of the NMDA channel following traumatic brain injury.
Traynelis, "Subunit-specific gating controls rat NR1/NR2A and NR1/NR2B NMDA channel
kinetics and synaptic signalling profiles," Journal of Physiology, vol.
Biochemical studies have also indicated the presence of a receptor in membrane fractions of hydra that binds to the NMDA channel
blocker, MK-801 (Pierobon et al., 2004a), and immunocytochemical studies provided evidence that NMDA receptors exist on the surface of nerve cells, nematocytes, myonemes of epitheliomuscular cells, and interstitial stem cells (Scappaticci et al., 2004).
Indeed, delivery of NMDA channel
blockers has been shown to effectively reduce RGC apoptosis in experimental rat glaucoma models [3, 6-8].
Even though this finding lends credibility to the role of NMDA receptors in mediation of long-term plasticity in the sensory-motor synapse of Aplysia, we should be cautious in interpreting the pharmacological experiments without a detailed characterization of the Aplysia NMDA channel
In particular, the rapid discharge within a burst would certainly lead to a temporal summation in the postsynaptic spine and dramatically increase the probability of calcium influx through postsynaptic NMDA channels
. The input-output properties of CNS synapses are an additional consideration.