Glutamine synthetase is a glial-specific marker in the olfactory regions of the lobster (Panulirus argus) nervous system.

Glutamine synthetase (GS) has been qualified as a very specific marker of astroglial-type neuroglia in vertebrate neural tissues. In this paper we have begun to examine the possibility that glial localization of GS could be a ubiquitous characteristic of complex nervous systems. To this end we have used immunohistochemistry to localize GS-like immunoreactivity in the olfactory regions of the complex nervous system of the arthropod, the spiny lobster Panulirus argus. We describe a novel method for affinity isolation of antibodies from crude serum. Using this approach we purified GS-specific antibodies to chick retina GS and used these to analyze the lobster brain and the primary olfactory organ. Western blots showed that the lobster brain contains an immunoreactive peptide with nearly the same molecular mass as that of chick retina GS. Northern blot analyses of mRNA and enzymatic activity assays also confirm that the lobster brain produces GS. Immunohistochemical staining of sectioned lobster olfactory lobes and sensory sensilla showed strong reactivity in specific cells. Comparison of the GS immunostaining pattern with that for FMRFamide, a well characterized marker of neurons in invertebrate neural tissues, it became clear that GS is indeed glial-specific in lobster neural tissues as it is in vertebrates. These results suggest that the compartmentalization of GS in non-neuronal cells is either an early step in neural evolution or is an obligate and fundamental characteristic of complex neural systems composed of both neurons and neuroglia.