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Distinct receptors for Leu- and Met-enkephalin on the metacerebral giant cell ofAplysia

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  1. 1.

    The effects ofd-Ala2-Leu-enkephalin (DALEU),d-Ala2-Met-enkephalin (DAMET), and FMRFamide on the metacerebral cell (MCC) ofAplysia were determined in current- and voltage-clamp experiments.

  2. 2.

    Distinct receptors exist on this neuron for the three substances.

  3. 3.

    DALEU elicited a depolarizing response due to an inward current but not accompanied by a significant change in membrane conductance.

  4. 4.

    In contrast, DAMET elicited a hyperpolarizing response due to an outward current, also not associated with a significant change in membrane conductance.

  5. 5.

    Both the DALEU and the DAMET responses increased with hyperpolarization, decreased with depolarization, but did not reverse at potentials less than -30 mV. Neither response was sensitive to naloxone.

  6. 6.

    FMRFamide induced a voltage-dependent outward current that reversed at about -76 mV. This neuron was responsive to much lower concentrations of FMRFamide than either of the enkephalins, and the response to FMRFamide appears to be a conductance increase to K+.

  7. 7.

    These results suggest that the MCC neuron has distinct receptors for Leuand Met-enkephalin that activate unusual responses of opposite polarity, as well as more usual inhibitory responses to FMRFamide.

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Correspondence to D. O. Carpenter.

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Kemenes, G., S.-Rózsa, K., Stefano, G. et al. Distinct receptors for Leu- and Met-enkephalin on the metacerebral giant cell ofAplysia . Cell Mol Neurobiol 12, 107–119 (1992). https://doi.org/10.1007/BF00713365

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Key words

  • opiates
  • FMRFamide
  • Aplysia neurons
  • voltage clamp