ABSTRACT
Dogs share many chronic morbidities with humans and thus represent a powerful model for translational research. In comparison to rodents, the canine ganglioside metabolism more closely resembles the human one. Gangliosides are components of the cell plasma membrane playing a role in neuronal development, intercellular communication and cellular differentiation. The present in vitro study aimed to characterize structural and functional changes induced by GM1 ganglioside (GM1) in canine dorsal root ganglia (DRG) neurons and interactions of GM1 with nerve growth factor (NGF) and fibroblast growth factor (FGF2) using immunofluorescence for several cellular proteins including neurofilaments, synaptophysin, and cleaved caspase 3, transmission electron microscopy, and electrophysiology. GM1 supplementation resulted in increased neurite outgrowth and neuronal survival. This was also observed in DRG neurons challenged with hypoxia mimicking neurodegenerative conditions due to disruptions of energy homeostasis. Immunofluorescence indicated an impact of GM1 on neurofilament phosphorylation, axonal transport, and synaptogenesis. An increased number of multivesicular bodies in GM1 treated neurons suggested metabolic changes. Electrophysiological changes induced by GM1 indicated an increased neuronal excitability. Summarized, GM1 has neurotrophic and neuroprotective effects on canine DRG neurons and induces functional changes. However, further studies are needed to clarify the therapeutic value of gangliosides in neurodegenerative diseases.
Subject(s)
Fibroblast Growth Factor 2/metabolism , G(M1) Ganglioside/metabolism , Nerve Growth Factor/metabolism , Nerve Growth Factors/metabolism , Animals , Cell Death/drug effects , Cell Survival/drug effects , Cells, Cultured , Dogs , Ganglia, Spinal/cytology , Ganglia, Spinal/metabolism , Ganglia, Spinal/physiology , Gangliosides/metabolism , Neurons/metabolism , Neuroprotective Agents/pharmacologyABSTRACT
The dorsal nucleus of the lateral lemniscus (DNLL) is an auditory brain stem structure that generates a long-lasting GABAergic output, which is important for binaural processing. Despite its importance in binaural processing, little is known about the cellular physiology and the synaptic input kinetics of DNLL neurons. To assess the relevant physiological parameters of DNLL neurons, their late postnatal developmental profile was analyzed in acute brain slices of 9- to 26-day-old Mongolian gerbils. The observed developmental changes in passive membrane and action potential (AP) properties all point toward an improvement of fast and precise signal integration in these neurons. Accordingly, synaptic glutamatergic and GABAergic current kinetics accelerate with age. The changes in intrinsic and synaptic properties contribute nearly equally to reduce the latency and jitter in AP generation and thus enhance the temporal precision of DNLL neurons. Furthermore, the size of the synaptic NMDA current is developmentally downregulated. Despite this developmental reduction, DNLL neurons display an NMDA-dependent postsynaptic amplification of AP generation, known to support high firing rates, throughout this developmental period. Taken together, our findings indicate that during late postnatal development DNLL neurons are optimized for high firing rates with high temporal precision.
Subject(s)
Biophysical Phenomena/physiology , Brain Stem/cytology , Brain Stem/growth & development , Gene Expression Regulation, Developmental/physiology , Sensory Receptor Cells/physiology , Synapses/physiology , Age Factors , Animals , Animals, Newborn , Auditory Pathways , Electric Stimulation , Excitatory Amino Acid Agents/pharmacology , Excitatory Postsynaptic Potentials/drug effects , Excitatory Postsynaptic Potentials/physiology , GABA Agents/pharmacology , Gerbillinae , In Vitro Techniques , Inhibitory Postsynaptic Potentials/drug effects , Inhibitory Postsynaptic Potentials/physiology , Membrane Potentials/physiology , Microscopy, Confocal , Nerve Net/cytology , Nerve Net/physiology , Nerve Tissue Proteins/metabolism , Patch-Clamp Techniques , Reaction Time/drug effects , Reaction Time/physiologyABSTRACT
Retinal glial Müller cells are characterized by dominant K(+) conductances. The cells may undergo changes of their membrane currents during ontogeny and gliosis as described in rabbit and man. Although the rat retina is often used in physiological experiments, the electrophysiology of rat Müller cells is less well studied. The aim of the present study was to characterize their membrane currents in postnatal development and in two models of retinal degeneration. Freshly isolated cells were subjected to whole-cell patch clamp recordings. During the first 4 weeks after birth of rats, their Müller cells displayed an increase in all membrane currents, particularly in the inward currents elicited at hyperpolarizing potentials. The decrease of the membrane resistance from more than 760 MOmega to less than 50 MOmega was accompanied by a shift of the zero current potential from about -20 mV to -80 mV, similar as earlier observed in developing rabbit Müller cells. These developmental changes were found in pigmented Brown Norway rats as well as in rats with inherited retinal dystrophy (RCS rats). Moreover, an infection of Lewis rats with the Borna disease virus caused substantial neuroretinal degeneration but did not result in a strong reduction of inward currents and of the zero current potential of the Müller cells. Thus, rat Müller cells fail to change their basic membrane properties in two different models of retinal pathology. This is in contrast to human and rabbit Müller cells, which have been shown to undergo dramatic changes of their membrane physiology in response to retinal diseases and injuries.
