{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,17]],"date-time":"2026-10-17T13:02:30Z","timestamp":1792242150057,"version":"4.4.0"},"reference-count":65,"publisher":"American Physiological Society","issue":"2","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Neurophysiology"],"published-print":{"date-parts":[[2008,2]]},"abstract":"<jats:p>Modulation of afterhyperpolarization (AHP) represents an important mechanism by which excitability of a neuron can be regulated. In the leech brain, sensitization enhances excitability of the S-cell, an interneuron thought to play an important role in this form of nonassociative learning. This increase in excitability is serotonin (5-HT) dependent, but it is not known whether changes in AHP contribute to 5-HT\u2013mediated enhancement of excitability. Therefore electrophysiological recordings and computational modeling were used to determine whether 5-HT enhances excitability via modulation of AHP. 5-HT reduced S-cell AHP and this decrease in the AHP corresponded with an increase in excitability. Little or no AHP is observed in the presence of Ca<jats:sup>2+<\/jats:sup>-free saline, suggesting the involvement of Ca<jats:sup>2+<\/jats:sup>-dependent K<jats:sup>+<\/jats:sup>channels. Furthermore, AHP amplitude decreased following treatment with drugs (tubocurare and charybdotoxin) that block Ca<jats:sup>2+<\/jats:sup>-dependent K<jats:sup>+<\/jats:sup>channel activity. The S-cell also exhibits an afterdepolarization (ADP), which is usually masked by the AHP, and was inhibited by the Na<jats:sup>+<\/jats:sup>channel blocker saxitoxin. A model of the S-cell AHP was constructed using two Ca<jats:sup>2+<\/jats:sup>-dependent K<jats:sup>+<\/jats:sup>currents and a Na<jats:sup>+<\/jats:sup>-driven ADP current. Reduction of the model conductances underlying the AHP to mimic the effects of 5-HT was sufficient to enhance excitability. These findings were confirmed in occlusion experiments in which pretreatment with tubocurare was able to block 5-HT\u2013mediated decreases in mAHP levels and increases in excitability. These data show that modulation of S-cell AHP can contribute to 5-HT\u2013mediated increases in excitability and that the S-cell afterpotential is due to the combined effects of AHP- and ADP-producing currents.<\/jats:p>","DOI":"10.1152\/jn.00989.2007","type":"journal-article","created":{"date-parts":[[2007,11,29]],"date-time":"2007-11-29T01:54:13Z","timestamp":1196301253000},"page":"605-616","source":"Crossref","is-referenced-by-count":13,"title":["Serotonergic Modulation of Afterhyperpolarization in a Neuron That Contributes to Learning in the Leech"],"prefix":"10.1152","volume":"99","author":[{"given":"Brian D.","family":"Burrell","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kevin 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