Serotonin, and mouse spinal neurones in cell culture

Two different responses to serotonin have been observed. One response was a depolarization accompanied by a decrease in membrane conductance. This response was enhanced at depolarized potentials and reduced at hyperpolarized potentials; the apparent conductance change was also reduced at hyperpolarized potentials indicating some voltage sensitivity of the response. The other response was a depolarization accompanied by an increased membrane conductance. The response was enhanced at hyperpolarized potentials and reversed to a hyperpolarization at -35 to -60 mV. The total number of responsive neurones was small (5%). This might be explained by a deficiency of serotonergic input to the recorded cells, since it was shown autoradiographically that very few neurones in the cultures used exhibited a specific high-affinity uptake for the transmitter, and hence probably contained it.