Reduction of voltage-dependent calcium currents in mumps virus-infected cultures of rat hippocampal neurons.
The effects of a mumps virus infection on functional properties of embryonic hippocampal neurons in culture were analysed with special emphasis on voltage-dependent Ca2+ channels. Cultures with higher or lower density of glial cells (not treated or treated with mitotic inhibitor, respectively) were infected with the relatively non-cytolytic RW strain of mumps virus and currents were recorded from neurons using whole cell voltage clamp. More than 65% of neurons and glial cells contained viral antigens 1-2 days post infection (p.i.). Glial cells remained infected 6-7 days p.i., while the ratio of infected versus uninfected neurons, especially in cultures with higher glial cell density, was reduced. In both infected and uninfected cultures the somal voltage-dependent Ca2+ currents were stronger in cultures with a higher glial cell density, which indicates that these currents are influenced by glial cells. Introduction of the virus into cultures caused a selective decrease in inward Ca2+ currents, which was most marked at days 6-7 p.i., and which included both infected and unifected neurons. Spontaneous synaptic currents and other ion channel conductances appeared normal in the infected cultures. Dantrolene, which inhibits release of Ca2+ from intracellular stores, decreased the neurons that died during the infection. Taken together the results show that a mumps viral infection can selectively alter the number of function of somal voltage dependent Ca2+ channels in immature hippocampal neurons and that this may reflect a disturbed glia-nerve cell interaction.