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Neurodegenerativne bolesti su progresivna, hronična i neizlečiva neurološka oboljenja. Pretpostavlja se da je u osnovi etiopatogeneze ovih oboljenja udruženo delovanje genetskih i sredinskih faktora. Potonji imaju sve veći značaj jer produžetak životnog veka ljudi vodi do prolongiranog izlaganja činiocima životne okoline. Jedan od mogućih sredinskih činilaca je 2,4-diaminobuterna kiselina (2,4-DABA), produkt ubikvitarnih cijanobakterija, čiji neurotoksični potencijal nije sasvim istražen.Metodima klasične elektrofiziologije i merenjem ulaznog otpora membrane ispitivani su učinci, jačina i mehanizmi delovanja 2,4-DABA na Retzius-ove neurone pijavice Haemopis sanguisuga. Naša istraživanja pokazuju da 2,4-DABA ima ekscitatoran učinak na neuronima, izazivajući izraženu depolarizaciju membranskog potencijala koja se razvija kroz dve faze, što je prvi put opisan fenomen na našem modelu. Istovetan učinak imaju i DL- i L- izoforma 2,4-DABA. Ekscitatorno dejstvo 2,4-DABA višestruko je jače od učinaka glutamata i aspartata, kao i od sredinskih ekscitatornih aminokiselina BOAA i BMAA. Depolarizacioni učinak 2,4-DABA je zavisan od prisustva Na+ i praćen povećanjem provodljivosti membrane Retzius-ovih neurona. Blokada non-NMDA glutamatnih receptora izaziva smanjenje amplitude prve faze depolarizacije, dok inhibicija transportnog sistema za neutralne aminokiseline upadljivo slabi drugu fazu depolarizacije. Zaključujemo da je 2,4-DABA snažna ekscitatorna aminokiselina koja ostvaruje svoj učinak preko jonotropnih glutamatnih receptora tokom prve faze i aktivacijom natrijum-zavisnog transportera za neutralne aminokiseline tokom druge faze depolarizacije. Ovi mehanizmi pokreću procese ključne za razvoj neurodegeneracije - ekscitotoksičnost, osmotsko opterećenje i smanjenje energetskih rezervi neurona, što uz dokazano globalno prisustvo 2,4-DABA ukazuje na značaj navedenih rezultata., Neurodegenerative diseases are chronic, progressive and incurable neurological illnesses. It is proposed that etiopathogenesis of these diseases is based on cooperation of genetic and environmental factors. The latter are of growing importance as life expectancy and exposure of people increase. A putative causative agent is 2,4 diaminobutyric acid (2,4-DABA), a product of ubiquitous cyanobacteria, whose neurotoxic potential is insufficiently examined. Using classical electrophysiology methods and measurements of input membrane resistance, we have investigated the effect, potency and mechanisms of 2,4-DABA effect on Retzius neurons of the leech Haemopis sanguisuga. Our results show that 2,4-DABA has an excitatory effect on neurons, eliciting extensive membrane depolarization that evolves through two distinct stages, which is a novel excitatory phenomenon reported on our model. Both L- and DL- isomers of 2,4-DABA cause equivalent depolarizing effects. Excitatory response of neurons to 2,4-DABA is several times larger than that induced by glutamate and aspartate or environmental excitatory amino acids BOAA and BMAA. Depolarizing action of 2,4-DABA is dependent on sodium ions and coupled with an increase of Retzius neuron membrane permeability. Blocking non-NMDA glutamate receptor reduces the amplitude of the first stage, while inhibition of the transport system for neutral amino acids markedly decreases the second phase of depolarization. We conclude that 2,4-DABA is a potent excitatory amino acid that activates ionotropic glutamate receptors during the first stage and sodium-dependent transporter for neutral amino acids during the second stage of depolarization. These mechanisms initiate processes crucial for neurodegeneration - excitotoxicity, osmotic stress and energy depletion of neurons, which the global presence of 2,4-DABA indicate the significance of our results.

Ion channels are often modulated by auxiliary subunits. Transmembrane AMPA receptor regulatory proteins (TARPs) are auxiliary subunits for AMPA-type glutamate receptors. These receptors are responsible for much of the fast excitatory synaptic transmission in the brain, and their mobility is thought to contribute to memory storage mechanisms. Although TARPs are known to modify AMPA receptor trafficking and gating in vitro, their contribution to in vivo AMPA receptor function is less clear.By generating mice lacking multiple TARP family members, we found that TARPs are functionally redundant. Single TARP knockout mice are viable, while those lacking multiple isoforms are often lethal. Consistent with molecular redundancy, AMPA receptor transmission in cerebellar Golgi cells is unaffected in single TARP knockout mice, but nearly eliminated in double knockouts. Unexpectedly, the remaining AMPA receptors have a different subunit composition, suggesting that TARPs may preferentially traffic GluR2 containing receptors.Our studies also highlight a role for TARPs in inhibitory neurons because AMPA receptor function in cerebellar Purkinje cells and Golgi cells is reduced in TARP knockout mice. Additionally, the loss of TARPs reduces the decay time of interneuron EPSCs. This indicates that AMPA receptor biophysical properties make a significant contribution to the time course of synaptic events, even at fast-decaying interneuron synapses.Our studies investigating TARP function in vivo also led to the discovery that TARPs profoundly change AMPA receptor pharmacology. Whereas CNQX is a competitive antagonist on AMPA receptors alone, it is a partial agonist on receptors containing any member of the TARP family and elicits depolarizing currents in neurons throughout the brain. By obtaining the crystal structure of CNQX bound to the AMPA receptor ligand-binding domain, we determined that CNQX induces a small amount of domain closure. Based on our findings, we propose an expanded mo

Stimulation of glutamate receptors induces neuronal nitric oxide (NO) release, which in turn modulates glutamate transmission. The involvement of ionotropic glutamate NMDA and AMPA/kainate receptors in induction of NO production in the rat brain was examined after injection of kainate, a non-NMDA receptor agonist; kainate plus 6-cyano- 7-nitroquinoxaline-2,3-dione (CNQX), a selective AMPA/kainate receptor antagonist; or kainate plus 2-amino-5-phosphonopentanoic acid (APV), a selective NMDA receptor antagonist. Competitive glutamate receptor antagonists were injected with kainate unilaterally into the CA3 region of the rat hippocampus. The accumulation of nitrite, the stable metabolite of NO, was measured by the Griess reaction at different times (5 min, 15 min, 2 h, 48 h, and 7 days) in hippocampus, forebrain cortex, striatum, and cerebellum homogenates. The used glutamate antagonists APV and CNQX both provided sufficient neuroprotection in the sense of reducing nitrite concentrations, but with different mechanisms and time dynamics. Our findings suggest that NMDA and AMPA/kainate receptors are differentially involved in nitric oxide production., Stimulacija glutamatskih receptora dovodi do stvaranja azot oksida (NO) u neuronima mozga što dovodi do modulacije glutamatske neurotransmisije. Ispitivana je uloga glutamatskih NMDA i AMPA/kainatnih receptora u stvaranju NO u mozgu pacova posle intracerebralne aplikacija kainata, agonista AMPA/kainatnih receptora, kainata sa 6-ciano-7- nitrokinoksalin-2,3-dionom (CNQX), selektivnim antagonistom AMPA/kainatnih receptora ili kainata sa 2-amino-5-fosfonopentanoiskom kiselinom (APV) selektivnim antagonistom NMDA receptora. Antagonisti glutamata su aplicirani unilateralno u selektivno osetljiv CA3 region hipokampusa. Stvaranje NO je praćeno preko akumulacije nitrita, stabilnih metabolita NO, Griess-ovom metodom. Merenja su vršena u hipokampusu, korteksu, stiatumu i cerebelumu mozga pacova 5 min, 15 min, 2 h, 48 h i 7 dana nakon aplikacije. U svim praćenim moždanim strukturama neuroprotektivno je delovala primena CNQX i APV u smislu smanjenja produkcije NO, ali sa očiglednom razlikom u mehanizmu dejstva i vremenskoj dinamici. Rezultati našeg istraživanja dokazuju da su glutamatski NMDA i AMPA/kainatni receptori različito uključeni u proces produkcije NO.