Electrophysiological responses of crayfish oocytes to biogenic amines.
Intracellular recordings were made from immature, growing oocytes of the crayfish Pacifastacus leniusciulus. Oocytes had a relatively negative resting potential of -74.7+/-2.2 mV (n=26; range -53 to -90) and a mean input resistance of 0.86+/-0.19 MOmega (n=22; range 0.17-3.3). Octopamine induced a long-lasting response involving biphasic changes in input resistance, together with bi- or multiphasic changes in membrane potential. The resistance-decreasing phase involved (in different oocytes) membrane hyperpolarization, depolarization or both. The resistance-increasing phase was usually a depolarization. The hyperpolarizing form of the resistance-decreasing response, and the depolarizing resistance-increasing response reversed in polarity at membrane potentials of (respectively) -90 and -92 mV, suggesting increases and decreases in K(+) conductance underly the biphasic changes in input resistance. The threshold concentration for the response was remarkably low (>10(-12) M) and showed little or no dose-dependence over the concentration range 10(-12)-10(-6) M. Similar responses were evoked by dopamine and serotonin (at 10(-9) M), although a higher proportion of oocytes responded to octopamine and/or dopamine than to serotonin.
Skorupski
P
P
School of Biological Sciences, Queen Mary and Westfield College, University of London, UK. p.skorupski@qmw.ac.uk
Melarange
R
R
D000818:Animals; D003400:Astacoidea; D001679:Biogenic Amines / Q000378:metabolism* / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009655:Octopamine / Q000378:metabolism / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010053:Ovary / Q000166:cytology; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology
D001679:Biogenic Amines; D009655:Octopamine; D012701:Serotonin; D004298:Dopamine