Endogenous PGE2 Regulates Membrane Excitability and Synaptic Transmission in Hippocampal CA1 Pyramidal Neurons

Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA.
Journal of Neurophysiology (Impact Factor: 2.89). 03/2005; 93(2):929-41. DOI: 10.1152/jn.00696.2004
Source: PubMed


The significance of cyclooxygenases (COXs), the rate-limiting enzymes that convert arachidonic acid (AA) to prostaglandins (PGs) in the brain, is unclear, although they have been implicated in inflammatory responses and in some neurological disorders such as epilepsy and Alzheimer's disease. Recent evidence that COX-2, which is expressed in postsynaptic dendritic spines, regulates PGE2 signaling in activity-dependent long-term synaptic plasticity at hippocampal perforant path-dentate granule cell synapses, suggests an important role of the COX-2-generated PGE2 in synaptic signaling. However, little is known of how endogenous PGE2 regulates neuronal signaling. Here we showed that endogenous PGE2 selectively regulates fundamental membrane and synaptic properties in the hippocampus. Somatic and dendritic membrane excitability was significantly reduced when endogenous PGE2 was eliminated with a selective COX-2 inhibitor in hippocampal CA1 pyramidal neurons in slices. Exogenous application of PGE2 produced significant increases in frequency of firing, excitatory postsynaptic potentials (EPSP) amplitude, and temporal summation in slices treated with the COX-2 inhibitor. The PGE2-induced increase in membrane excitability seemed to result from its inhibition of the potassium currents, which in turn, boosted dendritic Ca2+ influx during dendritic-depolarizing current injections. In addition, the PGE2-induced enhancement of EPSPs was blocked by eliminating both PKA and PKC activities. These findings indicate that endogenous PGE2 dynamically regulates membrane excitability, synaptic transmission, and plasticity and that the PGE2-induced synaptic modulation is mediated via cAMP-PKA and PKC pathways in rat hippocampal CA1 pyramidal neurons.

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Available from: Nicolas G Bazan, Mar 10, 2015
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    • "PGE2 can act on neuronal EP receptors directly. The application of PGE2 led to significant increases in firing frequency and excitatory postsynaptic potential (EPSP) amplitude in rat hippocampal slice cultures [74]. PGE2-induced increases in neuronal excitability may be partly attributable to an inhibition of potassium currents, resulting in boosted Ca2+ influx [74]. "
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    • "Excess PGE2 promotes excitatory signal transduction in the brain, leading to fever progression and behavioral abnormalities [8,9]. The concentration of PGE2 in the brain is increased by endotoxin challenge during infection [10,11]. "
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    • "Mechanistically, there is evidence that PGE2, released from post-synaptic dendritic spines can bind pre-synaptic prostaglandin receptors EP2 and/or EP4 and increase the amplitude of stimulus-evoked excitatory post-synaptic potentials (EPSPs) in the hippocampus (Sang et al.2005). This facilitatory role of basal COX-2 derived prostaglandins is dependent on the activity of cAMP-dependent protein kinase (Chen and Bazan 2005), the primary signalling pathway induced by EP2 and EP4 receptor activation. Thus with respect to memory function there are good reasons to believe that inhibition of COX-2 activity would be deleterious. "
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