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5‐HT inhibits N‐type but not L‐type Ca 2+ channels via 5‐HT 1A receptors in lamprey spinal neurons
Author(s) -
Hill Russell H.,
Svensson Erik,
Dewael Yannick,
Grillner Sten
Publication year - 2003
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2003.03051.x
Subject(s) - lamprey , chemistry , afterhyperpolarization , 5 ht receptor , agonist , neuroscience , apamin , receptor , pertussis toxin , sk channel , serotonin , biophysics , voltage dependent calcium channel , membrane potential , biology , potassium channel , ion channel , calcium , g protein , biochemistry , fishery , organic chemistry
5‐HT is a potent modulator of locomotor activity in vertebrates. In the lamprey, 5‐HT dramatically slows fictive swimming. At the neuronal level it reduces the postspike slow afterhyperpolarization (sAHP), which is due to apamin‐sensitive Ca 2+ ‐dependent K + channels (K Ca ). Indirect evidence in early experiments suggested that the sAHP reduction results from a direct action of 5‐HT on K Ca channels rather than an effect on the Ca 2+ entry during the action potential [Wallén et al ., (1989) J. Neurophysiol. , 61, 759–768]. In view of the characterization of different subtypes of Ca 2+ channels with very different properties, we now reinvestigate if there is a selective action of 5‐HT on a Ca 2+ channel subtype in dissociated spinal neurons in culture. 5‐HT reduced Ca 2+ currents from high voltage activated channels. N‐type, but not L‐type, Ca 2+ channel blockers abolished this 5‐HT‐induced reduction. It was also confirmed that 5‐HT depresses Ca 2+ currents in neurons, including motoneurons, in the intact spinal cord. 8‐OH‐DPAT, a 5‐HT 1A receptor agonist, also inhibited Ca 2+ currents in dissociated neurons. After incubation in pertussis toxin, to block G i/o proteins, 5‐HT did not reduce Ca 2+ currents, further indicating that the effect is caused by an activation of 5‐HT 1A receptors. As N‐type, but not L‐type, Ca 2+ channels are known to mediate the activation of K Ca channels and presynaptic transmitter release at lamprey synapses, the effects of 5‐HT reported here can contribute to a reduction in both actions.