Block of long-term potentiation by intracellular application of anti-phosphatidylinositol 4,5-bisphosphate antibody in hippocampal pyramidal neurons

Motor cortex stimulation for chronic pain

Motor cortex stimulation produces significant relief of symptoms in many forms of refractory chronic pain disorders.

Immunopharmacology--antibodies for specific modulation of proteins involved in neuronal function

The application of antibodies to living neurones has the potential to modulate function of specific proteins by virtue of their high specificity. This specificity has proven effective in determining the involvement of many proteins in neuronal function where specific agonists and antagonists do not exist, e.g. ion channel subunits. We discuss studies where antibodies modulate functions of voltage gated sodium, voltage gated potassium, voltage gated calcium hyperpolarisation activated cyclic nucleotide (HCN gated) and transient receptor potential (TRP) channels. Ligand gated channels studied in this way include nicotinic acetylcholine receptors, purinoceptors and GABA receptors. Antibodies have also helped reveal the involvement of different intracellular proteins in neuronal functions including G-proteins as well as other proteins involved in trafficking, phosphoinositide signalling and neurotransmitter release. Some suggestions for control experiments are made to help validate the method. We conclude that antibodies can be extremely valuable in determining the functions of specific proteins in living neurones in neuroscience research.

Modulation of synaptic transmission in hippocampal CA1 neurons by a novel neurotoxin (beta-pompilidotoxin) derived from wasp venom

We examined the effects of beta-pompilidotoxin (beta-PMTX), a neurotoxin derived from wasp venom, on synaptic transmission in the mammalian central nervous system (CNS). Using hippocampal slice preparations of rodents, we made both extracellular and intracellular recordings from the CA1 pyramidal neurons in response to stimulation of the Schaffer collateral/commissural fibers. Application of 5-10 microM beta-PMTX enhanced excitatory postsynaptic potentials (EPSPs) but suppressed the fast component of the inhibitory postsynaptic potentials (IPSPs). In the presence of 10 microM bicuculline, beta-PMTX potentiated EPSPs that were composed of both non-NMDA and NMDA receptor-mediated potentials. Potentiation of EPSPs was originated by repetitive firings of the presynaptic axons, causing summation of EPSPs. In the presence of 10 microM CNQX and 50 microM APV, beta-PMTX suppressed GABA(A) receptor-mediated fast IPSPs but retained GABA(B) receptor-mediated slow IPSPs. Our results suggest that beta-PMTX facilitates excitatory synaptic transmission by a presynaptic mechanism and that it causes overexcitation followed by block of the activity of some population of interneurons which regulate the activity of GABA(A) receptors.

Serotonin and acetylcholine are crucial to maintain hippocampal synapses and memory acquisition in rats

Treatment with serotonin and acetylcholine depletors reduced the number of synapses in the rat hippocampus. Animals that received the drug treatment lost a substantial number of synapses and showed an apparent impairment in memory acquisition. Although the animals were behaviorally impaired following the treatment, spatial memory was nonetheless eventually attained despite the disappearance of long-term potentiation. These data suggest that synapses in the hippocampus that are normally maintained by serotonin and acetylcholine are crucial for normal acquisition of spatial memory. The number of synapses maintained by biogenic amines may be a basic mechanism for neurobehavioral plasticity.

An electrophysiological and immunohistochemical study of the hippocampus of the reeler mutant mouse

The pyramidal cell layer in the CA1 subfield of the hippocampus of the reeler mouse is split into two laminae, the deep and the superficial. We examined the electrophysiological properties of double-layered CA1 pyramidal neurons in the reeler mouse hippocampal slice in vitro. We also studied cytoarchitectonic abnormalities in the hippocampus of this mutant by immunohistochemical methods using anti-parvalbumin and anti-F3/F11-protein antibodies. Laminar analysis of the postsynaptic field potentials in the CA1 subfield of the reeler hippocampus revealed broad negative field potentials with double negative peaks. In the CA1 subfield of the reeler mouse, tetanic stimulation of Schaffer collateral/commissural fibers induced long-term potentiation (LTP) in the majority of the deep layers (near alveus) examined, but very rarely in the superficial layer (near the molecular layer). Immunohistochemical study showed that parvalbumin-immunopositive neurons were densely concentrated in the hippocampus of the reeler mouse, especially in the stratum radiatum and the stratum lacunosum-molecular, in which only a few parvalbumin-immunoreactive neurons were seen in the normal mouse. Abnormal trajectories of axons arising from malpositioned pyramidal cells in the CA1 subfield of the reeler mouse were identified by F3/F11 immunohistochemistry. Interestingly, F3/F11-immunoreactive Schaffer collaterals were misdirected in the CA1 subfield of this mutant. The present electrophysiological and immunohistochemical data suggest that impairment of LTP in the superficial layer of the CA1 pyramidal neurons appears to be mainly due to strong inhibitory inputs to this malpositioned population of neurons.

Inositol 1,3,4,5-tetrakisphosphate as a mediator of neuronal death in ischemic hippocampus

Selective death of CA1 pyramidal neurons after transient forebrain ischemia has attracted interest for its possible relation to the pathogenesis of memory deficits and dementia. Using whole cell patch-clamp recording from CA1 pyramidal neurons in hippocampal slices of gerbils after ischemia we studied the intracellular signaling mechanisms related to the phosphoinositide cycle. Intracellular application of an antibody against phosphatidylinositol 4,5-bisphosphate rescued ischemic neurons from stimulus-induced irreversible depolarization. Furthermore, application of inositol 1,3,4,5-tetrakisphosphate in normal cells caused an irreversible depolarization in response to synaptic input, which mimicked the deterioration of ischemic neurons. Depolarization of both ischemic and normal neurons in the presence of inositol 1,3,4,5-tetrakisphosphate was prevented by the addition of the Ca2+ chelator, 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetate. Application of antibody against inositol 1,4,5-triphosphate 3-kinase, which blocks formation of inositol 1,3,4,5-tetrakisphosphate, also protected against cell deterioration. Our results suggest that the vulnerability of hippocampal pyramidal neurons following ischemia is caused by a disturbed phosphoinositide cascade, with one metabolite, inositol 1,3,4,5-tetrakisphosphate, playing a key role in the induction of Ca2+ accumulation, which leads to neuronal death.