Intracellular chloride activity and the effect of 5-hydroxytryptamine on the chloride conductance of leech Retzius neurons.
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.
Munsch
T
T
Institut für Zoologie/Neurobiologie, Heinrich-Heine Universität, Düsseldorf, Germany.
Schlue
W R
WR
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects*; D002712:Chlorides / Q000378:metabolism*; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000187:drug effects; D007865:Leeches / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology*
D018118:Chloride Channels; D002712:Chlorides; D012701:Serotonin