Hypothermia translocates nitric oxide synthase from cytosol to membrane in snail neurons

A review of the actions of Nitric Oxide in development and neuronal function in major invertebrate model systems

Ever since the late-eighties when endothelium-derived relaxing factor was found to be the gas nitric oxide, endogenous nitric oxide production has been observed in virtually all animal groups tested and additionally in plants, diatoms, slime molds and bacteria. The fact that this new messenger was actually a gas and therefore didn't obey the established rules of neurotransmission made it even more intriguing. In just 30 years there is now too much information for useful comprehensive reviews even if limited to animals alone. Therefore this review attempts to survey the actions of nitric oxide on development and neuronal function in selected major invertebrate models only so allowing some detailed discussion but still covering most of the primary references. Invertebrate model systems have some very useful advantages over more expensive and demanding animal models such as large, easily identifiable neurons and simple circuits in tissues that are typically far easier to keep viable. A table summarizing this information along with the major relevant references has been included for convenience.

Initial studies on the direct and modulatory effects of nitric oxide on an identified central Helix aspersa neuron

The generation of the novel messenger molecule nitric oxide (NO) has been demonstrated in many tissues across phyla including nervous systems. It is produced on demand by the enzyme nitric oxide synthase often stimulated by intracellular calcium and typically affecting guanylate cyclase thought to be its principal target in an auto and/or paracrine fashion. This results in the generation of the secondary messenger cyclic guanosine monophosphate (cGMP). Nitric oxide synthase has been demonstrated in various mollusk brains and manipulation of NO levels has been shown to affect behavior in mollusks. Apart from modulation of the effect of the peptide GSPYFVamide, there appears little published on direct or modulatory effects of NO on Helix aspersa central neurons. We present here initial results to show that NO can be generated in the region around F1 in the right parietal ganglion and that NO and cGMP directly hyperpolarize this neuron. For example, application of the NO-donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP; 200 µM) can cause a mean hyperpolarization of 41.7 mV, while 2 mM 8-bromo-cyclic guanosine monophosphate (8-bromo-cGMP) produced a mean hyperpolarization of 33.4 mV. Additionally, pre-exposure to NO-donors or cGMP appears to significantly reduce or even eliminates the normal hyperpolarizing K(+)-mediated response to dopamine (DA) by this neuron; 200 µM SNAP abolishes a standard response to 0.5 µM DA while 1 mM 8-bromo-cGMP reduces it 62%.

Molecular and cellular pathways as a target of therapeutic hypothermia: pharmacological aspect

Induced therapeutic hypothermia is the one of the most effective tools against brain injury and inflammation. Even though its beneficial effects are well known, there are a lot of pitfalls to overcome, since the potential adverse effects of systemic hypothermia are still troublesome. Without the knowledge of the precise mechanisms of hypothermia, it will be difficult to tackle the application of hypothermia in clinical fields. Better understanding of the characteristics and modes of hypothermic actions may further extend the usage of hypothermia by developing novel drugs based on the hypothermic mechanisms or by combining hypothermia with other therapeutic modalities such as neuroprotective drugs. In this review, we describe the potential therapeutic targets for the development of new drugs, with a focus on signal pathways, gene expression, and structural changes of cells. Theapeutic hypothermia has been shown to attenuate neuroinflammation by reducing the production of reactive oxygen species and proinflammatory mediators in the central nervous system. Along with the mechanism-based drug targets, applications of therapeutic hypothermia in combination with drug treatment will also be discussed in this review.