The localization of two voltage-gated calcium channels in the pyloric network of the lobster stomatogastric ganglion

Abstract

Voltage-gated calcium channels are critical to all aspects of nervous system function, with differing roles within the neuronal somata, at synaptic terminals, and at the neuromuscular junction. We have developed antibodies against two voltage-gated Ca 2+ channel genes from the spiny lobster, Panulirus interruptus, which are homologous to the Drosophila Ca1A (a P/Q-type channel) and Ca1D (an L-type channel) genes. Using these antibodies, we have found that each channel shows unique patterns of localization within the stomatogastric nervous system. Both antibodies stain somata of most of the neurons in the pyloric network to varying degrees. The high degree of variability in staining intensity within individual pyloric cell classes supports the hypothesis of Golowasch et al. (1999a,b) that individual cells can vary in their composition of ionic currents and still have similar firing properties. Anti-Ca1A stains structures in the neuropil, some of which are terminals of axons descending from higher ganglia; however, the majority of these are neither neurites nor blood vessels, but may instead be glial cells or other support elements. Anti-Ca1A labeling was also prominent in the peripheral axons of pyloric motoneurons as they enter muscles, indicating that this channel may be involved in regulation of synaptic transmission onto the foregut muscles. Anti-Ca1D does not label neurites in the neuropil of the stomatogastric ganglion. It stains glial cells in the stomatogastric ganglion in the region of their nuclei, presumably from protein being produced in the perinuclear rough endoplasmic reticulum, en route to the glial cell periphery. While anti-Ca1D labeling is seen in a patchy distribution along peripheral pyloric axons, it was never seen near the muscle. We conclude that the localization of these two calcium channels is tightly controlled within the stomatogastric nervous system, but we cannot conclusively demonstrate that Ca1A and/or Ca1D channels play roles in synaptic integration within the stomatogastric ganglion.