Role for glial cells in regulating the functional expression of neuropeptide Y (NPY) neurons in aggregate cultures derived from dissociated fetal brain cells.

A series of studies from our laboratory have established an aggregate culture system of fetal rat brain cells expressing neuropeptide Y (NPY) which can serve as a model to study the role of glia-neuron paracrine interactions in the developmental expression of NPY neurons. In this system, NPY production increases progressively with culture-age and it is induced by forskolin (FOR) and phorbol 12-myristate 13-acetate (PMA). We addressed the following question: Is the functional expression of the NPY neurons impaired in the absence of glial cells (particularly astrocytes) and if so, can secretory products of aggregates composed of the full complement of brain cells (intact aggregates) restore the function of the impaired NPY neurons? Aggregates were generated from 17-day-old fetal rat cortex and maintained in serum-free medium for 13-15 days. Cytosine arabinoside (CA; doses of 0.5-8 microM) was added to the cultures on day 1 and the effectiveness in elimination of glial cells was verified on day 15 by measuring the incorporation of 3H thymidine into DNA and by immunostaining for the astrocyte marker glial fibrillary acidic protein (GFAP). Basal NPY production and FOR (10 microM) + PMA (20 nM) stimulated production of NPY on days 13-15 were taken as functional criteria. FOR + PMA induced approximately 2-fold increase in NPY production in control cultures (no CA). CA inhibited both basal and FOR + PMA induced production of NPY and DNA synthesis in a dose-dependent manner: at 6 microM CA, basal NPY production was reduced by about 50%, FOR + PMA stimulated production of NPY and DNA synthesis were completely inhibited, and astrocytes were essentially eliminated.(ABSTRACT TRUNCATED AT 250 WORDS)