MODULATION OF IDENTIFIED STOMATOGASTRIC GANGLION NEURONS IN PRIMARY-CELL CULTURE

1. We studied the properties of identified stomatogastric ganglion (ST G) neurons grown in complete isolation in primary cell culture. 2. STG neurons isolated with a short piece of primary neurite adhered to the culture dishes and extended neurites. Outgrowth was apparent within s everal hours, and continued for less-than-or-equal-to 5 days. 3. After 1 day in culture, most STG neurons were not capable of producing acti on potentials or oscillations. After 3-5 days in culture, most STG neu rons regained the ability to fire action potentials, and some became e ndogenous bursters. Neurons in culture 3-5 days possessed many of the physiological properties of STG neurons in situ, including postinhibit ory rebound, a hyperpolarization-activated depolarizing voltage sag, a nd the ability to burst in the presence of the potassium channel block er tetraethylammonium. 4. Identified cultured neurons responded approp riately to a variety of neuromodulators, including the monoamines dopa mine and octopamine, the muscarinic agonist pilocarpine, and the pepti de proctolin. These data suggest that the maintenance of receptor expr ession in fully differentiated STG neurons is not affected by isolatio n from all synaptic and modulatory influences. 5. In contrast to the o ther modulators tested, the effects of serotonin on cultured neurons d iffered from those reported in situ. Two cell types that are reported to be hyperpolarized by serotonin in situ, the lateral pyloric and pyl oric neurons, were depolarized by serotonin in culture.