Intracellular chloride activity and the effect of 5-hydroxytryptamine on the chloride conductance of leech Retzius neurons

Eur J Neurosci. 1993 Dec 1;5(12):1551-7. doi: 10.1111/j.1460-9568.1993.tb00225.x.


Intracellular Cl- activity (aCli) and 5-hydroxytryptamine (5-HT)-induced membrane currents of Retzius neurons in the central nervous system of the medicinal leech were measured using Cl- sensitive microelectrodes and a two-microelectrode voltage-clamp technique. At the membrane of Retzius neurons Cl- ions were not passively distributed. Under different conditions the chloride equilibrium potential (ECl, -60.1 mV for isotonic saline and -57.8 mV for a hypertonic saline) was negative with respect to the membrane potential (Em, -55 +/- 3.8 and -47 +/- 3.4 mV respectively). The endogenous neurohormone 5-HT always polarized the membrane of Retzius neurons in the direction of ECl. When voltage-clamping the membrane of Retzius neurons near the resting potential both in situ and in primary culture, application of 5-HT produced an outward current (I5-HT) and an increase in membrane conductance. Current-voltage relationships for I5-HT showed a slight outward rectification and reversal potentials of -61.6 +/- 3.1 mV in situ and -66 +/- 3.1 mV in primary culture, both values being comparable to the ECl of Retzius neurons as measured in situ. The results indicate that 5-HT increases the Cl- conductance of Retzius neurons, thereby hyperpolarizing the cell membrane and affecting both the excitability of the neuron and 5-HT release from it. This could affect the feeding and swimming behaviour of the leech.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Behavior, Animal / drug effects
  • Behavior, Animal / physiology
  • Cell Membrane / drug effects
  • Cells, Cultured
  • Chloride Channels / drug effects*
  • Chlorides / metabolism*
  • Ganglia, Invertebrate / cytology
  • Ganglia, Invertebrate / drug effects
  • Leeches / metabolism*
  • Membrane Potentials / drug effects
  • Microelectrodes
  • Neurons / drug effects
  • Neurons / metabolism*
  • Serotonin / pharmacology*


  • Chloride Channels
  • Chlorides
  • Serotonin