Phytocannabinoide sind Terpenphenole aus Cannabis spec. Sie binden im Gehirn u.a. an den CB1-Rezeptor, der beispielsweise auch an Membranen dopaminerger Neurone der Substantia nigra zu finden ist, welche bei Morbus Parkinson (MP) degenerieren. Ein Grund für den Zelltod ist die hohe Empfindlichkeit der dopaminergen Neurone gegenüber oxidativem Stress. In Zellkulturmodellen für MP wird er durch Komplex-I-Inhibitoren hervorgerufen, z.B. durch das Pestizid Rotenon. Da Phytocannabinoide auch antioxidative Eigenschaften aufweisen, wurde in unserer Studie untersucht, ob ein CB1-Rezeptoragonist, Tetrahydrocannabinol (THC), und ein Cannabinoid mit geringer Affinität zum CB1-Rezeptor, Cannabidiol (CBD), im Rotenon-Modell wirksam sind.

Phytocannabinoids (PCs) are terpenphenoles deriving from Cannabis species. In the brain, their activity is mediated by specific receptors such as the cannabinoid receptor 1 (CB1) or 2. These receptors are widely expressed in the brain. PCs as well have antioxidative capacities. Since one major event in PD is oxidative stress, cannabinoids are suggested as neuroprotective drugs. Oxidative stress can be induced by the complex I inhibitor rotenone. We investigated the effects of tetrahydrocannabinol (THC) and cannabidiol (CBD) on rotenone affected dissociated mesencephalic cultures and neuroblastoma cells (N18TG2) of mice. Cannabinoids (0.1 to 10µM) were administered alone or concomitantly with rotenone (80nM) for 48h. Rotenone treatment resulted in a degeneration of about 20% of the dopaminergic cells which was counteracted significantly by THC and CBD at 10µM. A significant restoration of glutathione levels in rotenone treated cultures at 0.1µM of THC and 10µM of CBD was also found. Electron spin resonance spectroscopy in N18TG2 cells revealed that the amount of superoxide radicals in cells exposed to rotenone nearly doubled. Neither THC nor CBD counteracted this increase. Thus radical scavenging does not appear to be the main mechanism of PCs action. The mechanisms which lead to the observed effects remain to be investigated, but cannabinoids might be candidates for neuroprotective agents in disorders linked to oxidative stress.

Phytocannabinoids (PCs) affect cells by receptor binding and non-receptor mediated mechanisms. They are discussed as putative drugs in neurodegenerative diseases. In our study, we investigated the effects of cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), cannabidivarine (CBDV), and tetrahydrocannabinol (THC) on murine dissociated mesencephalic cultures and neuroblastoma (N18TG2) cells. Cannabinoids (0.1 to 10µM) were administered for 48h to either cell culture. In mesencephalic cultures, dopaminergic neurons (DNs) were counted. Most PCs did not alter the number of DNs, only THC increased the count significantly (up to 118% at 10µM), whereas CBD administration led to a decrease of cell number by 20% (10µM). Glutathione levels were unchanged while all cannabinoids have similar radical scavenging characteristic (250µg Trolox/mg substance) except THC which showed nearly doubled values in a DPPH assay (280µg Trolox/mg substance). N18TG2 cells showed some vulnerability to most PCs. As shown by alamar blue assay and propidium iodide uptake measurements. A slight reduction of cell degeneration could be detected only at high doses of THC. Increased survival cells in THC treated cultures might be related to its radical scavenging abilities.

The stilben resveratrol is a phytoalexin found in red wine grapes and is discussed as an antioxidative and anti-inflammatory neuroprotective compound. Resveratrol interacts with the complex III of the respiratory chain and is therefore not just a radical scavenger, but also a substance suppressing radical formation in the mitochondria. In this study, resveratrol was used to investigate its effects on glutamate damages. Excitotoxicity leads to increased formation of superoxide radicals. Therefore, in mesencephalic cell cultures of mice, we studied the influence of trans-resveratrol on the survival rate of dopaminergic neurons and propidium iodide uptake (uPI) after glutamate exposure. On the 10th DIV, glutamate (0, 0.5, or 5mM) was added to the cultures for 15min, and then the cultures were incubated further (48h) in resveratrol-containing (0, 0.01, 0.1, or 1µM) medium. The number of dopaminergic cells remained unaltered when cultures were exposed to resveratrol alone. The compound did not alter the dopaminergic cell number in cultures that were treated with 0.5mM of glutamate, but after exposure to 5mM of the amino acid, resveratrol nearly doubled the number of surviving dopaminergic neurons. At lower concentrations of resveratrol (0.1µM), the uPI was decreased by 28% (0.5mM glutamate) or by 16% (5mM glutamate), respectively. In this study, partial beneficial action of resveratrol (to a concentration up to 0.1µM) in a mesencephalic culture system after glutamate affection could be shown.

Introduction Gabapentin is a potent anticonvulsant though with not fully clarified mode of action. Effects on amino acid transport and direct affinity to neurotransmitter receptors (e.g. gamma-amino-butyric acid, GABA) and their postsynaptic effector systems are suspected. In our study, we exposed bicuculline, a GABA(A) receptor antagonist, to hippocampal slice cultures. Such organotypic cultures are used in particular in epilepsy research for testing anticonvulsants, as they offer a versatile test model due to their proximity to the in vivo situation. Material and methods On postnatal days 6-8, from hippocampi of Sprague-Dawley rats coronal sections were prepared and cultivated on Millicell-CM-membranes for 9 days. Between day 6 and day 9, bicuculline, gabapentin or either substance were administered to the cultures at a concentration of 100 micromolar before harvesting the slices. Degenerative or compensatory changes of receptor densities of glutamatergic and GABAergic receptors were immunohistochemically quantified by specific antibodies against the glutamate receptors GluR2 and NMDAR2, the GABA(A) receptor, and against neurofilament proteins. Results Treatment with gabapentin alone resulted in a significant reduction of the NMDAR2 density in the Cornu ammonis 1 (CA1) region of the hippocampus of about 36 % compared to controls. Bicuculline-induced significant increases of the densities of neurofilament proteins and GluR2 receptors of about 100 and 18 %, respectively, could be counteracted by the antiepileptic drug. In this region, partially compensatory effects of gabapentin in bicuculline cotreated cultures could be detected. Conclusion In this study we have shown that bicuculline-induced changes of receptor densities in an in vitro model for epilepsy can be partly abolished by treatment with gabapentin. The balancing of the receptor densities for glutamate and GABA, the most important transmitters in the hippocampus, by gabapentin underlines its suitability for drug therapy in epilepsy.

Oxidative stress evoked by excitotoxicity is considered an important factor for the loss of dopaminergic neurons in Parkinson’s disease. In vitro, protective effects of the dopamine agonist lisuride on complex I inhibition in primary dopaminergic cell culture have been reported. However, little is known about the effects of lisuride on glutamate-induced radical formation. Here, effects of lisuride on the formation of nitric oxide (NO) and superoxide radicals following glutamate exposure were studied on primary cell cultures prepared from mouse mesencephala. Glutamate treatment resulted in doubling of NO and superoxide radical formation, increased dopaminergic cell degeneration and extensively altered neuronal appearance. Pretreatment with lisuride significantly lowered the levels of either reactive species and increased the survival of dopaminergic neurons compared to glutamate-treated cultures. Moreover, the beneficial effect of lisuride could be completely inhibited by the D2/D3 receptor antagonist sulpiride when co-treated in cultures.