The adolescent brain and age-related behavioral manifestations

Glutamate neurotoxicity and diseases of the nervous system

Nitric oxide (NO), apparently identical to endothelium-derived relaxing factor in blood vessels, is also formed by cytotoxic macrophages, in adrenal gland and in brain tissue, where it mediates the stimulation by glutamate of cyclic GMP formation in the cerebellum Stimulation of intestinal or anococcygeal nerves liberates NO, and the resultant muscle relaxation is blocked by arginine derivatives that inhibit NO synthesis It is, however, unclear whether in brain or intestine, NO released following nerve stimulation is formed in neurons, glia, fibroblasts, muscle or blood cells, all of which occur in proximity to neurons and so could account for effects of nerve stimulation on cGMP and muscle tone We have now localized NO synthase protein immunohistochemically in the rat using antisera to the purified enzyme We demonstrate NO synthase in the brain to be exclusively associated with discrete neuronal populations NO synthase is also concentrated in the neural innervation of the posterior pituitary, in autonomic nerve fibres in the retina, in cell bodies and nerve fibres in the myenteric plexus of the intestine, in adrenal medulla, and in vascular endothelial cells These prominent neural localizations provide the first conclusive evidence for a strong association of NO with neurons

Localization of nitric oxide synthase indicating a neural role for nitric oxide

Excitotoxicity refers to the ability of glutamate or related excitatory amino acids to mediate the death of central neurons under certain conditions, for example, after intense exposure. Such excitotoxic neuronal death may contribute to the pathogenesis of brain or spinal cord injury associated with several human disease states. Excitotoxicity has substantial cellular specificity and, in most cases, is mediated by glutamate receptors. On average, NMDA receptors activation may be able to trigger lethal injury more rapidly than AMPA or kainate receptor activation, perhaps reflecting a greater ability to induce calcium influx and subsequent cellular calcium overload. It is possible that excitotoxic death may share some mechanisms with other forms of neuronal death.

Excitotoxic cell death

The metabotropic glutamate receptors: structure and functions.

L-Glutamic, L-aspartic acids and a number of their structural analogs, including quisqualic, kainic, ibotenic, quinolinic, and N-methyl-D- aspartic (NMDA) acids, increase inositol phospholipid hydrolysis when added to primary cultures of cerebellar granule cells, as is reflected by an enhanced formation of 3H-inositolmonophosphate (3H-IP1) in the presence of Li+ L-Glutamic acid also enhances the formation of the initial products of inositol phospholipid hydrolysis, 3H-inositol di- (3H-IP2) and triphosphate (3H-IP3) In the absence of extracellular Ca2+, L-glutamic acid fails to enhance 3H-IP1 formation, but still increases 3H-IP2 and 3H-IP3 formation The stimulation of 3H-IP1 formation elicited by L-glutamic acid is reduced by DL-2-amino-5- phosphonovaleric acid (APV) and gamma-glutamylglycine and, to a lesser extent, by 2,3-cis-piperidindicarboxylic acid (PDA) The stimulation of 3H-IP1 formation by kainic acid is antagonized by PDA and gamma- glutamylglycine, but it is almost unaffected by APV The increase in 3H- IP1 formation elicited by quisqualic acid is not reduced by any of the dicarboxylic amino acid receptor antagonists that we have tested We conclude that different subtypes of excitatory amino acid recognition sites are associated with inositol phospholipid metabolism in primary cultures of cerebellar granule cells

https://www.jneurosci.org/content/jneuro/6/7/1905.full.pdf

The activation of inositol phospholipid metabolism as a signal-transducing system for excitatory amino acids in primary cultures of cerebellar granule cells.

Primary cultures of cerebellar granule cells have been used in pharmacologically and functionally characterizing excitatory amino acid recognition sites coupled with guanylate cyclase. When granule cells were incubated in physiological culture conditions (Locke's solution, pH 7.4), only kainate and, to a lesser extent, L-glutamate increased cyclic GMP (cGMP) levels. Under these conditions, L-aspartate, N-methyl- D-aspartate (NMDA), and quisqualate were inactive. When granule cells were incubated in the absence of extracellular Mg2+ or in the presence of the depolarizing agent veratrine, L-glutamate, L-aspartate, and NMDA became as effective as kainate in enhancing cGMP formation. The action of kainate was preferentially antagonized by 2,3-cis- piperidindicarboxylate, whereas the action of L-glutamate was preferentially antagonized by (+/-)2-amino-5-phosphonovalerate. These data suggest that 2 different excitatory amino acid recognition sites (activated by kainate or by L-glutamate, L-aspartate, and NMDA, respectively) are coupled with guanylate cyclase in primary cultures of cerebellar granule cells: While the coupling of the recognition site for kainate with guanylate cyclase operates under resting conditions and in the presence of Mg2+, the coupling of the recognition site for L- glutamate, L-aspartate, and NMDA with guanylate cyclase requires depolarizing conditions or the absence of extracellular Mg2+.

https://www.jneurosci.org/content/jneuro/7/1/40.full.pdf

Excitatory amino acid receptors coupled with guanylate cyclase in primary cultures of cerebellar granule cells

Distribution and characterization of diazepam binding inhibitor (DBI) in peripheral tissues of rat

A vascular thrombotic lesion localized to the rat sensorimotor cortex was produced following intravenous injection of the photosensitive dye rose bengal, and its activation with a small beam of high-intensity white light focused to the skull overlaying the sensorimotor cortex In the sensorimotor cortex at various times after the triggering event, two contiguous brain regions with different degree(s) of neuronal damage can be distinguished: (1) a primary thrombotic ischemic core where the majority of cells are dead and (2) a penumbra region surrounding the core lesion in which a slower progressive neuronal degeneration is occurring Importantly, in both brain regions the neuronal degeneration is associated with the activation and persistent translocation of protein kinase C (PKC) as indicated by an increase in 4-beta-3H-phorbol-12,13-dibutyrate (3H-PDBu) binding Moreover, the demonstration that in the area penumbra the neuronal degeneration and the persistent translocation of PKC can be inhibited by a pretreatment with dizocilpine (ie, MK-801) indicates that the dynamics of the progression of the neuronal degeneration are maintained by glutamate accumulating in the extraneuronal fluids MK-801 additionally prevents the transcriptional activation of several immediate-early genes (IEGs) (eg, c-fos) and their cognate third nuclear messenger (ie, c-Fos) expression present in the hemisphere ipsilateral to the lesion On the other hand, LIGA4 and LIGA20 derivatives of GM1 lysoganglioside reduce the membrane translocation of PKC and the neuronal damage in the penumbra area, but fail to change the increase of IEG expression in the cortex ipsilateral to the lesion

https://www.jneurosci.org/content/jneuro/13/6/2483.full.pdf

Semisynthetic sphingolipids prevent protein kinase C translocation and neuronal damage in the perifocal area following a photochemically induced thrombotic brain cortical lesion

Cellular and subcellular localization of an octadecaneuropeptide derived from diazepam binding inhibitor: immunohistochemical studies in the rat brain.

Alessandro Guidotti

Papers

The activation of inositol phospholipid metabolism as a signal-transducing system for excitatory amino acids in primary cultures of cerebellar granule cells.

Excitatory amino acid receptors coupled with guanylate cyclase in primary cultures of cerebellar granule cells

Distribution and characterization of diazepam binding inhibitor (DBI) in peripheral tissues of rat

Semisynthetic sphingolipids prevent protein kinase C translocation and neuronal damage in the perifocal area following a photochemically induced thrombotic brain cortical lesion

Cellular and subcellular localization of an octadecaneuropeptide derived from diazepam binding inhibitor: immunohistochemical studies in the rat brain.