Veratridine increases the survival of retinal ganglion cells in vitro

Intl J of Devlp Neuroscience

2001

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The control of natural cell death is mediated by neurotrophins released by target, afferent and glial cells. In the present work we show that treatment of retinal cells 'in vitro' for 48 h with 25 microM carbamylcholine induced a two-fold increase in retinal ganglion cells survival. This effect was dose-dependent and mediated by M1 receptors since it could be blocked by 1 microM telenzepine (a M1 receptor antagonist) and mimicked by 200 microM oxotremorine (a M1 receptor agonist). The effect of carbamylcholine was abolished by 10 microM BAPTA-AM (an intracellular Ca2+ chelator), 30 microM dantrolene (an inhibitor of ryanodinic receptors), 500 nM H-89 (an inhibitor of PKA), 1.25 microM chelerythrine chloride (an inhibitor of PKC) and 50 microM PD-98059 (a MEK inhibitor). Treatment with 10 microM genistein (an inhibitor of tyrosine kinase), 25 microM LY-294002 (a PI-3 kinase blocker), 30 nM brefeldin-A (a blocker of polypeptides release), 50 nM K-252a (a Trk receptor inhibitor) and 20 microM fluorodeoxyuridine (an inhibitor of cell proliferation) totally inhibited the effect of carbamylcholine. Taken together our results indicate that muscarinic activity controls the survival of retinal ganglion cells through a mechanism involving the release of polypeptides and activation of Irk receptors.

Section: Discussionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 86%

Cholinergic activity modulates the survival of retinal ganglion cells in culture: the role of M₁ muscarinic receptors

Pereira

Medina

Intl J of Devlp Neuroscience

2001

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“…In a previous study, Pereira and Araujo (29) demonstrated that 3 µM veratridine increased the survival of retinal ganglion cells, an effect also mediated by acetylcholine. These investigators showed that the veratridine effect was not mediated by L-type calcium channels but was mediated by T-type calcium channels.…”

Section: Discussionmentioning

confidence: 93%

Cyclic AMP increases the survival of ganglion cells in mixed retinal cell cultures in the absence of exogenous neurotrophic molecules, an effect that involves cholinergic activity

Santos

2001

Braz J Med Biol Res

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Natural cell death is a well-known degenerative phenomenon occurring during development of the nervous system. The role of trophic molecules produced by target and afferent cells as well as by glial cells has been extensively demonstrated. Literature data demonstrate that cAMP can modulate the survival of neuronal cells. Cultures of mixed retinal cells were treated with forskolin (an activator of the enzyme adenylyl cyclase) for 48 h. The results show that 50 µM forskolin induced a two-fold increase in the survival of retinal ganglion cells (RGCs) in the absence of exogenous trophic factors. This effect was dose dependent and abolished by 1 µM H89 (an inhibitor of protein kinase A), 1.25 µM chelerythrine chloride (an inhibitor of protein kinase C), 50 µM PD 98059 (an inhibitor of MEK), 25 µM Ly 294002 (an inhibitor of phosphatidylinositol-3 kinase), 30 nM brefeldin A (an inhibitor of polypeptide release), and 10 µM genistein or 1 ng/ml herbimycin (inhibitors of tyrosine kinase enzymes). The inhibition of muscarinic receptors by 10 µM atropine or 1 µM telenzepine also blocked the effect of forskolin. When we used 25 µM BAPTA, an intracellular calcium chelator, as well as 20 µM 5-fluoro-2'-deoxyuridine, an inhibitor of cell proliferation, we also abolished the effect. Our results indicate that cAMP plays an important role controlling the survival of RGCs. This effect is directly dependent on M1 receptor activation indicating that cholinergic activity mediates the increase in RGC survival. We propose a model which involves cholinergic amacrine cells and glial cells in the increase of RGC survival elicited by forskolin treatment. Correspondence

“…In a previous work we showed that veratridine induced a twofold increase on the survival of retinal ganglion cells maintained 'in vitro' for 48 h. The effect was dose-dependent (maximal response obtained with 3 mM veratridine) and inhibited either by 1 mM tetrodotoxin (a voltage dependent Na + channel inhibitor) or by 30 mM flunarizine (an inhibitor of T-type Ca 2 + channels) [39]. In the present work we show that the effect of veratridine is mediated by intracellular Ca 2 + release and by the activation of tyrosine kinase enzymes.…”

Section: Introductionmentioning

confidence: 95%

Chronic depolarization induced by veratridine increases the survival of rat retinal ganglion cells ‘in vitro’

Pereira

Intl J of Devlp Neuroscience

2000

During the last decades it has been shown that trophic molecules released by target, afferent and glial cells play a pivotal role controlling neuronal cell death. Trophic molecules are able to inhibit this regressive event during development as well as during degenerative diseases. One of the mechanisms involved in the control of neuronal survival by afferent cells requires the release of trophic molecules stimulated by electrical activity. It has been demonstrated that veratridine (a depolarizing agent that keeps the Na(+) channels opened) induces an increase in neuronal survival. In the present work we show that 3 µM veratridine induced a two-fold increase on the survival of retinal ganglion cells after 48 h in culture. The veratridine effect was inhibited by 50 µM amiloride (an inhibitor of Ca(2+) channels), 25 µM benzamil (an inhibitor of Na(+) channels), 30 µM dantrolene and 7.5 µM caffeine (both inhibitors of Ca(2+) release from the endoplasmatic reticulum) and 10 µM BAPTA-AM (an intracellular Ca(2+) chelator). However, 5 µM nifedipine (a selective inhibitor of voltage-dependent L-type Ca(2+) channels) and 100 µM MK 801 (an inhibitor of NMDA receptors) did not block the veratridine effect. On the other hand, treatment with 10 µM genistein (an inhibitor of tyrosine kinase enzymes), 20 µM fluorodeoxyuridine (an inhibitor of cell proliferation) or 10 µM atropine (an antagonist of muscarinic receptors) completely abolished the effect of veratridine. Taken together, our results indicate that veratridine increases the survival of rat retinal ganglion cells through mechanisms involving Na(+) influx, intracellular Ca(2+) release, activation of tyrosine kinase enzymes and cellular proliferation. They also indicate that cholinergic activity plays an important role in the veratridine effect.