Serotonin elicits long-lasting enhancement of rhythmic respiratory activity in turtle brain stems in vitro

J Appl Physiol (1985). 2001 Dec;91(6):2703-12. doi: 10.1152/jappl.2001.91.6.2703.


Brain stem preparations from adult turtles were used to determine how bath-applied serotonin (5-HT) alters respiration-related hypoglossal activity in a mature vertebrate. 5-HT (5-20 microM) reversibly decreased integrated burst amplitude by approximately 45% (P < 0.05); burst frequency decreased in a dose-dependent manner with 20 microM abolishing bursts in 9 of 13 preparations (P < 0.05). These 5-HT-dependent effects were mimicked by application of a 5-HT(1A) agonist, but not a 5-HT(1B) agonist, and were abolished by the broad-spectrum 5-HT antagonist, methiothepin. During 5-HT (20 microM) washout, frequency rebounded to levels above the original baseline for 40 min (P < 0.05) and remained above baseline for 2 h. A 5-HT(3) antagonist (tropesitron) blocked the post-5-HT rebound and persistent frequency increase. A 5-HT(3) agonist (phenylbiguanide) increased frequency during and after bath application (P < 0.05). When phenylbiguanide was applied to the brain stem of brain stem/spinal cord preparations, there was a persistent frequency increase (P < 0.05), but neither spinal-expiratory nor -inspiratory burst amplitude were altered. The 5-HT(3) receptor-dependent persistent frequency increase represents a unique model of plasticity in vertebrate rhythm generation.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Brain Stem / drug effects*
  • Brain Stem / physiology*
  • Electrophysiology
  • Hypoglossal Nerve / physiology
  • In Vitro Techniques
  • Periodicity*
  • Receptors, Serotonin / physiology
  • Receptors, Serotonin, 5-HT1
  • Respiration / drug effects*
  • Serotonin / pharmacology*
  • Time Factors
  • Turtles / physiology*


  • Receptors, Serotonin
  • Receptors, Serotonin, 5-HT1
  • Serotonin