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PubMed1984

Sensitivity of Aplysia neurons in primary culture to putative neurotransmitters.

Aplysia neurons grown in primary cell culture (Dagan and Levitan, 1981) were exposed to the putative neurotransmitters acetylcholine and serotonin by local iontophoretic application, and changes in membrane potential or voltage clamp currents were examined. It was found that 47% of the neurons were sensitive to cholinergic agonists, 14% to serotonin, and 9% responded to both. Responses could be recorded upon application of the transmitters to the cell bodies as well as along the regenerated neurites. An identified group of neurons, the neurosecretory bag cells, exhibited similar responses to cholinergic agonists in culture and in situ. Pleural medial neurons exhibited cholinergic responses in culture similar to those previously reported in situ. Thus neurotransmitter receptor/ion channel complexes characteristic for a specific cell type in the intact ganglion are also present on this cell type in culture.

Acetylcholine↗

PubMed1984

Chemical and electrotonic connections between Aplysia neurons in primary culture.

Dissociated Aplysia neurons will regenerate neurites and form functional connections in primary cell cultures. The specificity of intercellular connectivity in these cultures was investigated by coculturing neurosecretory bag cells with neurons dissociated from the buccal ganglion. It was found that bag-bag and buccal-buccal electrotonic synapses form with high frequency, consistent with previous findings in pure bag and buccal cultures. There is specificity in the formation of these connections, since no bag-buccal electrotonic synapses were observed. Chemical interactions, on the other hand, are present between bag and buccal neurons. In a buccal-bag pair, injection of sufficient depolarizing current into the buccal cell to elicit a train of action potentials leads to a slow hyperpolarizing response in the bag cell. The bag cell hyperpolarization is accompanied by an increase in the cell's input conductance. This connection appears to be unidirectional, produces a voltage shift in the bag cell which is opposite in sign to that in the buccal cell, and is blocked by the removal of Ca2+ from the extracellular medium, indicating that it is mediated by a chemical neurotransmitter. The selective formation of electrotonic synapses in these mixed bag-buccal cultures, together with the presence of chemically mediated interactions, make this system particularly useful for investigating the establishment of intercellular connectivity.

Animals↗