The actions of cholecystokinin octapeptide (CCK) on the membrane properties of mouse spinal neurons grown in monolayer culture were examined using intracellular recording techniques. In a subpopulation of cells, application of CCK (0.2-100 μM) by pressure ejection from micropipettes produced a small (∼2 mV) membrane depolarization that was accompanied by a decrease in membrane conductance (∼11 percent). These effects were associated with an enhanced tendency of the cells to generate action potentials when stimulated with intracellular depolarizing current. The unsulfated analog of CCK, which possesses weak biological activity in the gut, had little or no effect on cultured spinal neurons. A number of differences were noted between the responses to CCK and the excitatory amino acid glutamate. First, the effects of CCK were more delayed in onset (∼17 sec) and prolonged in duration (∼124 sec). Second, the depolarizations produced by glutamate were of larger magnitude and associated with variable effects on membrane conductance. Third, the response to CCK showed tachyphylaxis with repeated applications whereas glutamate remained effective as often as it was applied. It is concluded that CCK facilitates the excitability of spinal neurons in a manner distinct from that of the conventional excitant glutamate.
- Cell culture
- Cholecystokinin octapeptide
- Intracellular recording
- Spinal cord
- Unsulphated cholecystokinin octapeptide
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience