Abstract
The modulation of high-voltage-activated (HVA) Ca 2+ channels by serotonin (5-HT) was studied in ventromedial hypothalamic (VMH) neurons acutely dissociated from 12–14-day-old Wistar rats using the whole-cell and nystatin perforated-patch recording configurations. 5-HT inhibited the HVA Ca 2+ channels in a concentration-, time- and voltage-dependent manner. This inhibition was mimicked by the 5-HT 1A agonist 8-hydroxy-dipropylaminotetralin and was prevented by pretreatment with pertussis toxin (PTX). ω-Conotoxin-GVIA, ω-agatoxin-IVA, nicardipine and ω-conotoxin-MVIIC blocked each fraction of HVA Ca 2+ channel currents, suggesting the existence of N-, P-, L- and Q-types of HVA Ca 2+ channels. A component of the current resistant to these Ca 2+ channel antagonists also existed in the VMH neurons. Among these five components of HVA Ca 2+ channel currents, the N- and Q-type currents were significantly inhibited by 5-HT. These findings suggest that the activation of 5-HT 1A receptors produces the selective inhibition of N- and Q-type Ca 2+ channels through a PTX-sensitive G-protein in rat VMH neurons.
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