Distinct receptors for Leu- and Met-enkephalin on the metacerebral giant cell of Aplysia.
1. The effects of D-Ala2-Leu-enkephalin (DALEU), D-Ala2-Met-enkephalin (DAMET), and FMRFamide on the metacerebral cell (MCC) of Aplysia were determined in current- and voltage-clamp experiments. 2. Distinct receptors exist on this neuron for the three substances. 3. DALEU elicited a depolarizing response due to an inward current but not accompanied by a significant change in membrane conductance. 4. In contrast, DAMET elicited a hyperpolarizing response due to an outward current, also not associated with a significant change in membrane conductance. 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. 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. These results suggest that the MCC neuron has distinct receptors for Leu- and Met-enkephalin that activate unusual responses of opposite polarity, as well as more usual inhibitory responses to FMRFamide.
Kemenes
G
G
Balaton Limnological Research Institute of the Hungarian Academy of Sciences, Tihany.
Rózsa
K S
KS
Stefano
G
G
Carpenter
D O
DO
D000200:Action Potentials / Q000187:drug effects; D000595:Amino Acid Sequence; D000818:Animals; D001048:Aplysia / Q000378:metabolism*; D004743:Enkephalin, Leucine / Q000378:metabolism*; D016308:Enkephalin, Leucine-2-Alanine / Q000378:metabolism / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D019835:FMRFamide; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism / Q000494:pharmacology; D011957:Receptors, Opioid / Q000145:classification* / Q000187:drug effects / Q000378:metabolism
D009479:Neuropeptides; D011957:Receptors, Opioid; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; C013801:enkephalin-Met, Ala(2)-; D016308:Enkephalin, Leucine-2-Alanine; D019835:FMRFamide