Ubiquinone Protects Cultured Neurons Against Spontaneous and Excitotoxin-Induced Degeneration Ubiquinone protects cultured neurons against spontaneous and excitotoxin-induced degeneration

Ubiquinone is an endogenous quinone with pharmacological actions mainly related to its antioxidant properties. Here we report that ubiquinone protects cultured cerebellar granule cells against glutamate-induced neurotoxicity. In control cultures at 9 days of maturation in vitro (DIV), a 30-min exposure to 100 microM glutamate induced neuronal degeneration, as reflected by the great percentage (greater than 90\%) of cells labeled with propidium iodide 24 h after the exposure. Glutamate-induced neuronal death was dramatically reduced in cultures treated daily with ubiquinone since the second DIV. In these cultures, glutamate failed to induce a "delayed" increase in the influx of 45Ca2+, an established parameter of excitotoxicity. Similarly, repeated addition of ubiquinone attenuated in a concentration-dependent manner the age-dependent degeneration of granule cells that is due to the toxic action of the endogenous glutamate progressively released into the medium. These results suggest that ubiquinone may be a useful drug in the therapy of acute and chronic neurodegenerative diseases related to hyperactivity of excitatory amino acid neurotransmission

Estrogen modulates stimulation of inositol phospholipid hydrolysis by norepinephrine in rat brain slices.

The influence of estrogen on stimulation of inositol phospholipid hydrolysis by norepinephrine and carbamylcholine has been studied by measuring the accumulation of [3H]inositol-monophosphate ([3H]InsP) in cortical, hippocampal and striatal slices from ovariectomized rats. Repeated (but not a single) subcutaneous injections of estradiol benzoate (EB) (2 micrograms/animal once every 2 days for 10 days) markedly reduced stimulation of inositol phospholipid hydrolysis by norepinephrine in hippocampus and corpus striatum. Conversely, the efficacy of norepinephrine was increased in cortical slices. Estrogen treatment did not affect basal or carbamylcholine-stimulated [3H]InsP formation. In vitro addition of 17 beta-estradiol (1-100 nM) failed to modify norepinephrine- or carbamylcholine-induced [3H]InsP production in all regions examined. An increased density of alpha 1-adrenergic binding sites in cortical membranes paralleled the enhanced responsiveness of inositol phospholipid hydrolysis to norepinephrine induced by EB treatment in this area, whereas no significant changes in [3H]prazosin binding were found in membranes from hippocampus and corpus striatum. These results indicate that estrogen may affect inositol phospholipid hydrolysis in discrete brain areas, suggesting a complex role for estradiol in modulating noradrenergic receptor activity in the central nervous system

PHORBOL ESTERS ATTENUATE GLUTAMATE-STIMULATED INOSITOL PHOSPHOLIPID HYDROLYSIS IN NEURONAL CULTURES

The phorbol diesters 12-O-tetradecanoylphorbol-13-acetate (TPA) and phorbol-12,13-dibutyrate, but not 4-α-phorbol-didecanoate, inhibited the stimulation of inositol phospholipid hydrolysis by excitatory amino acids and carbamylcholine in primary cultures of cerebellar neurons. This inhibition was mimicked by the synthetic diacylglycerol 1,2-dioleoyl-rac-glycerol (DOG) and was selective for a specific glutamate-phosphoinositide receptor subtype (GP2 receptor) activated by glutamate and quisqualate. TPA was nearly inactive in inhibiting the stimulation of inositol phospholipid hydrolysis by N-methyl-D-aspartate, a selective agonist of the GP1 receptor. Phorbol diesters and DOG attenuated the stimulation of inositol phospholipid hydrolysis by glutamate and quisqualate also in cerebellar slices from 9-15-day-old rats; however, using this preparation, their action was weak and required high concentrations (>1 μM). The inhibition of signal transduction by phorbol diesters was not consequent to a reduced binding of glutamate to its membrane recognition sites. In fact, TPA induced only a small increase in the K(D) but not change in the B(max) of [3H]glutamate binding in cerebellar membranes. Phorbol diesters may act to inhibit specific GTP-binding proteins or particular forms of phosphoinositidase C associated with GP2 or muscarinic cholinergic receptors

Estrogen modulates stimulation of inositol phospholipid hydrolysis by norepinephrine in rat brain slices

The influence of estrogen on stimulation of inositol phospholipid hydrolysis by norepinephrine and carbamylcholine has been studied by measuring the accumulation of [3H]inositol-monophosphate ([3H]InsP) in cortical, hippocampal and striatal slices from ovariectomized rats. Repeated (but not a single) subcutaneous injections of estradiol benzoate (EB) (2 micrograms/animal once every 2 days for 10 days) markedly reduced stimulation of inositol phospholipid hydrolysis by norepinephrine in hippocampus and corpus striatum. Conversely, the efficacy of norepinephrine was increased in cortical slices. Estrogen treatment did not affect basal or carbamylcholine-stimulated [3H]InsP formation. In vitro addition of 17 beta-estradiol (1-100 nM) failed to modify norepinephrine- or carbamylcholine-induced [3H]InsP production in all regions examined. An increased density of alpha 1-adrenergic binding sites in cortical membranes paralleled the enhanced responsiveness of inositol phospholipid hydrolysis to norepinephrine induced by EB treatment in this area, whereas no significant changes in [3H]prazosin binding were found in membranes from hippocampus and corpus striatum. These results indicate that estrogen may affect inositol phospholipid hydrolysis in discrete brain areas, suggesting a complex role for estradiol in modulating noradrenergic receptor activity in the central nervous system

Repeated calcitonin treatment reduces the stimulation of inositol phospholipid by norepinephrine and serotonin in rat hippocampus and cerebral cortex.

Stimulation of inositol phospholipid hydrolysis by norepinephrine or 5-hydroxytryptamine was reduced in hippocampal or cortical slices from rats repeatedly injected with (Asu1.7)eel-calcitonin (2.5 IU/kg i.p.). This effect was specific, as the basal or carbamylcholine-stimulated inositol phospholipid hydrolysis was unchanged in slices from calcitonin-injected animals. The reduced responsiveness to norepinephrine did not reflect a decreased number or affinity of alpha 1-adrenergic recognition sites, suggesting that calcitonin treatment leads to a reduced coupling between alpha 1-adrenoceptors and phospholipase C