Serotonin preferentially hyperpolarizes capsaicin-sensitive C type sensory neurons by activating 5-HT1A receptors

Brain Res. 1992 Jul 10;585(1-2):212-8. doi: 10.1016/0006-8993(92)91209-w.


The effects of serotonin (5-HT) were investigated by intracellular recording from 179 dorsal root ganglion (DRG) cells classified by conduction velocity. Bath applied 5-HT depolarized 82% and hyperpolarized 4% of the A-type cells. In C-type cells, 5-HT depolarized only 41%, but hyperpolarized 39% of the cells. The depolarizing responses were of two types; an increase or decrease in R(in), mediated by 5-HT2or3 receptors, respectively. These receptors were observed in both A- and C-type cells. Hyperpolarizing responses were largely confined to A(delta)- and C-type cells. Carboxamidotryptamine and 8-OH-dipropylamino-tetralin were full agonists in eliciting hyperpolarization, and metitepin, spiperone and spiroxitrine behaved as competitive antagonists. This indicated that hyperpolarization was mediated by a 5-HT1A receptor. A 5-HT1A&3 receptor were found co-localized on some C-type cells. A strong depolarizing response to capsaicin was observed in the subgroup of C-type neurons that were also hyperpolarized by 5-HT. Thus a co-localization of capsaicin and 5-HT1A receptors was also observed.

MeSH terms

  • Animals
  • Capsaicin / pharmacology*
  • Electrophysiology
  • Ganglia, Spinal / drug effects
  • Ganglia, Spinal / physiology
  • Neurons, Afferent / drug effects*
  • Neurons, Afferent / physiology
  • Receptors, Serotonin / physiology*
  • Serotonin / pharmacology*


  • Receptors, Serotonin
  • Serotonin
  • Capsaicin