Exogenous gangliosides induce direct voltage and conductance changes on isolated neurons

Effect of ganglioside on synaptic plasticity of hippocampus in lead-exposed rats in vivo

Synaptic plasticity, including long-term potentiation (LTP), long-term depression (LTD) and depotentiation (DP), is important for learning and memory. Previous studies proved that chronic lead exposure especially during early post-natal development induced impairment on synapse plasticity. The purpose of this study is to evaluate the effect of ganglioside on the lead-induced impairments of LTP and DP in rat dentate gyrus in vivo. The experiments were carried out in three groups of rats (control, lead-exposed, ganglioside-treated lead-exposed, respectively). The input-output (I/O) function, pair pulses reaction, excitatory post-synaptic potential (EPSP) and population spike (PS) amplitude were measured in the dentate gyrus (DG) of adult rats (70-90 days) in response to stimulation applied to the lateral perforant path. The results show that (1) chronic lead exposure impaired LTP/DP measured on both EPSP slope and PS amplitude in DG area of the hippocampus. (2) The amplitudes of LTP/DP of lead-exposed group were significantly increased by supplying ganglioside. These results suggest intraperitoneally injection with ganglioside could reverse the lead-induced impairments of synaptic plasticity in rats and might be effective in attenuating the cognitive deficits induced by lead.

Gangliosides stimulate calcium flux in neuro-2A cells and require exogenous calcium for neuritogenesis

The neuritogenic effect of exogenous ganglioside has been documented with a variety of neuronal and neuroblastoma systems, but the mechanism is not understood. Involvement of Ca2+ is suggested by this study which demonstrates that treatment of Neuro-2A cells with bovine brain gangliosides (BBG) in Ca2(+)-depleted medium failed to produce neurite outgrowth. This was in contrast to treatment with retinoic acid or dibutyryl cyclic AMP which induced differentiation under the same conditions. Addition of BBG to Neuro-2A cells caused small, but significant, increases in both influx and efflux of Ca2+. It thus appears that although neuritogenesis can proceed by more than one mechanism, that induced by BBG requires exogenous Ca2+ and involves stimulation of Ca2+ flux.

The role(s) of gangliosides in neural differentiation and repair: a perspective

Gangliosides, sialylated glycosphingolipids, are found in greatest concentration in the brain. While they were first characterized as a unique class of lipids almost 50 years ago, little is known regarding their actual function. It is known that (a) ganglioside composition changes during development, (b) different types of neural cells have specific gangliosides associated with them, (c) the accumulation of gangliosides in certain inborn errors of metabolism results in the formation of aberrant meganeurites, and (d) gangliosides appear to enhance recovery from certain neural traumas. Recent work suggests that it is the oligosaccharide portion of the ganglioside that carries much of the biological specificity. Coupled with observations that ganglioside-binding proteins are present on the plasma membranes of cells, it suggests the hypothesis that gangliosides present on the surface of one cell may interact with specific ganglioside-binding proteins, "receptors," on target cells. As a result of the ganglioside-binding protein interaction, a signal could be transmitted to the cell. This might occur via modulation of the effect of the endogenous ganglioside on the activity of a kinase(s) or by an alteration in ionic flux. The signal would initiate the appropriate cellular response.

Ganglioside function in the development and repair of the nervous system. From basic science to clinical application

Gangliosides play important roles in the normal physiological operations of the nervous system, in particular that of the brain. Changes in ganglioside composition occur in the mammalian brain not only during development, but also in aging and in several neuropathological situations. Gangliosides may modulate the ability of the brain to modify its response to cues or signals from the microenvironment. For example, cultured neurons are known to respond to exogenous ganglioside with changes characteristic of cell differentiation. Gangliosides can amplify the responses of neurons to extrinsic protein factors (neuronotrophic factors) that are normal constituents of the neuron's environment. The systemic administration of monosialoganglioside also potentiates trophic actions in vivo and improves neural responses following various types of injury to the adult mammalian central nervous system. The possible molecular mechanism(s) underlying the ganglioside effects may reflect an action in modulating ligand-receptor linked transfer of information across the plasma membrane of the cell.

Effects of exogenous ganglioside and cholesterol application on excitability of Aplysia neurons

The effects of pressure-ejected gangliosides GM1 and GMix ("Cronassial") and cholesterol dissolved in sea water on the electrophysiological characteristics of Aplysia neurons were studied using voltage-clamp recording techniques. Two types of electrophysiological effects were found. In about 5% of neurons brief pulses (0.1-0.2 sec) of GM1 or GMix elicited fast and large currents associated with an increase in membrane conductance and clear reversal potentials. These currents were similar to those elicited by common neuro-transmitters. Thus it appears that gangliosides may activate a membrane-bound receptor on at least some neurons. Most (about 85%) of the 121 neurons studied showed responses to longer pulses (1.0-2.5 sec) of gangliosides. These responses were much smaller, usually had a relatively slow component, and could be mimicked by application of cholesterol. The currents elicited were either inward or outward and were often biphasic, with an small initial outward component followed by a larger slow inward current. The responses often became larger upon repeated application at short intervals, and long periods of wash were required for recovery. This type of response appears to reflect changes in the electrical properties of the cell induced by incorporation of small amounts of gangliosides or cholesterol into the membrane.