Journal of Comparative Physiology A

, Volume 168, Issue 2, pp 165–177

Two forms of sensitization of the local bending reflex of the medicinal leech

  • S. R. Lockery
  • W. B. KristanJr.
Review Article

DOI: 10.1007/BF00218409

Cite this article as:
Lockery, S.R. & Kristan, W.B. J Comp Physiol A (1991) 168: 165. doi:10.1007/BF00218409


Sensitization of the local bending reflex of the medicinal leech Hirudo medicinalis was studied in a semi-intact preparation in which behavioral and electrophysiological recordings were made simultaneously.
  1. 1.

    Sensitization of local bending could be produced in two ways: by repeated stimulation of the mechanoreceptor sensitive to pressure (the P cell), and by stimutlation of the mechanoreceptor sensitive to noxious stimuli (the N cell).

  2. 2.

    Both forms of sensitization produced a central neuronal change, measured as an increase in the number of stimulus-evoked action potentials in cell 3 (an excitor of dorsal longitudinal muscles).

  3. 3.

    Intracellular stimulation of serotonin-containing neurons 21 and 61 mimicked the sensitizing stimuli, but stimulation of the Retzius cell, which also contains serotonin, did not.

  4. 4.

    Stimulation of the Leydig cell, which releases octopamine, decreased the strength of local bending.


Key words

Leech Sensitization Neural correlates Serotonin 



analysis of variance


dorsal posterior nerve


Leydig cell


Retzius cell

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • S. R. Lockery
    • 1
  • W. B. KristanJr.
    • 2
  1. 1.CNL, Salk InstituteSan DiegoUSA
  2. 2.Department of BiologyUniversity of California San DiegoLa JollaUSA

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