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Serotonergic inhibition of the T-type and high voltage-activated Ca2+ currents in the primary sensory neurons of Xenopus larvae.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Sun, Qing Quan Dale, Nicholas |
| Copyright Year | 1997 |
| Abstract | The primary sensory Rohon-Beard (R-B) neurons of Xenopus larvae are highly analogous to the C fibers of the mammalian pain pathway. We explored the actions of 5-HT by studying the modulation of Ca2+ currents. In approximately 80% of the acutely isolated R-B neurons, 5-HT inhibited the high voltage-activated (HVA) currents by 16% (n = 29) and the T-type currents by 24% (n = 41). The modulation of the T-type and the HVA currents was mimicked by selective 5-HT1A and 5-HT1D agonists: 8-OH-DPAT and L-694,247. The effects of the agonists were blocked by their respective 5-HT1A or 5-HT1D antagonists: p-MPPI and GR127935, suggesting that both 5-HT1A and 5-HT1D receptors were involved. Approximately 70% of the actions of 5-HT on HVA currents was occluded by omega-conotoxin-GVIA (N-type channel blocker), whereas the rest of the modulation ( approximately 30%) was occluded by <100 nM omega-agatoxin-TK (P/Q-type channel blocker). This suggests that 5-HT acts on N- and P/Q-type Ca2+ channels. Neither the modulation of the T-type nor that of the HVA currents was accompanied by changes in their voltage-dependent kinetics. Cell-attached patch-clamp recordings suggest that the modulation of the T-type channel occurs through a membrane-delimited second messenger. We have studied the functional consequences of the modulation of T-type Ca2+ channels and have found that these channels play a role in spike initiation in R-B neurons. Modulation of T-type channels by 5-HT therefore could modulate the sensitivity of this sensory pathway by increasing the thresholds of R-B neurons. This is a new and potentially important locus for modulation of sensory pathways in vertebrates. |
| Starting Page | 19 |
| Ending Page | 34 |
| Page Count | 16 |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.jneurosci.org/content/jneuro/17/18/6839.full.pdf |
| PubMed reference number | 9278519v1 |
| Volume Number | 17 |
| Issue Number | 18 |
| Journal | The Journal of neuroscience : the official journal of the Society for Neuroscience |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Afferent neuron Calcium ion Cognitive function: initiation Conotoxin Eighty Homovanillic Acid Kinetics (discipline) L 694247 Larva Mammals Obstruction Pain Serotonin Tissue membrane newton omega-Conotoxin GVIA omega-Conotoxins voltage |
| Content Type | Text |
| Resource Type | Article |
