. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. A Excitability (2 nA) A1 ASW NEUROMODULATION IN APLYS1A B Action Potential 255 -45 mV *• A2 +CAMP 0 mV - -I - -45 mV J A3 (ASW + cAMP) + 5-HT -45 mV. (ASW + cAMP) + 5-HT 5 ms -45 mV l/V 200 ms 50 mV Figure 5. Differential effects of an analogue ofcAMP and 5-HT on the duration of the action potential and excitability in tail sensory neurons. Recordings were made from somata that had been isolated surgically from the pleural ganglion. (A) A 1 s. 2 nA depolarizing current pulse elicited three action potentials in artifical seaw
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. A Excitability (2 nA) A1 ASW NEUROMODULATION IN APLYS1A B Action Potential 255 -45 mV *• A2 +CAMP 0 mV - -I - -45 mV J A3 (ASW + cAMP) + 5-HT -45 mV. (ASW + cAMP) + 5-HT 5 ms -45 mV l/V 200 ms 50 mV Figure 5. Differential effects of an analogue ofcAMP and 5-HT on the duration of the action potential and excitability in tail sensory neurons. Recordings were made from somata that had been isolated surgically from the pleural ganglion. (A) A 1 s. 2 nA depolarizing current pulse elicited three action potentials in artifical seawater (A1). An identical current pulse elicited twice as many action potentials alter hath application of 8-pcpt-cAMP (A2). The subsequent addition of serotonin to the bath, which still contained 8-pcpt-cAMP, did not increase further the number of spikes during the pulse (A3). (B) In the same sensory neuron, bath application of 8-pcpt-cAMP (50 pM) increased the duration of the somatic action potential by a modest amount. The subsequent addition of serotonin (50 pM) to the bath, which still contained 8-pcpt-cAMP. dramatically increased the duration of the action potential. (From Baxter and Byrne. 1990). potential by an average of 17% (Fig. 5B). The subsequent addition of serotonin to the bath, which still contained the cAMP analogue, further increased the duration of the action potential by an additional 230%, on average. Thus, cAMP has modest effects on spike broadening that are not sufficient to occlude the effects of serotonin. The differential effects of serotonin and cAMP can be accounted for by the actions of these compounds on spe- cific membrane currents. Use of voltage-clamp and com- puter-subtraction techniques has shown that cAMP re- duces a potassium current, the S-current, that is activated at relatively negative membrane potentials, does not in- activate and is relatively insensitive to block by TEA (Klein et al, 1982; Pollock el ai. 1985; Shuster and Sie- gelbaum
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
