My. Kim et al., CHEMOSENSORY ADAPTATION IN PARAMECIUM INVOLVES CHANGES IN BOTH REPELLENT BINDING AND THE CONSEQUENT RECEPTOR POTENTIALS, Comparative biochemistry and physiology. Section A: Comparative physiology, 118(3), 1997, pp. 589-597
Citations number
32
Categorie Soggetti
Physiology,Biology
Journal title
Comparative biochemistry and physiology. Section A: Comparative physiology
Two different chemorepellents, GTP and lysozyme, both produce transien
t depolarizing somatic receptor potentials and backward swimming (at m
icromolar concentrations) in Paramecium. Behavioral adaptation occurs
after 10 min in either repellent and the cells regain normal forward s
wimming. This is very specific for each repellent. Cells that have beh
aviorally adapted to 0.1 mu M lysozyme (for 10 min) show forward swimm
ing in lysozyme, a decreased amplitude of lysozyme-induced depolarizat
ions and a 10-fold decrease in the estimated number of surface binding
sites for H-3-lysozyme (by Scatchard analysis). All of these changes
are reversible after 10 min in the absence of lysozyme. The lysozyme-a
dapted cells have normal responses to other depolarizing stimuli such
as 8 mM Ba++, 40 mM K+, 10 mM Na+ and 10.0 mu M GTP and to the hyperpo
larizing chemoattractant, 5 mM acetate. Their surface binding of P-32-
GTP was also unaffected. GTP-adapted cells show dramatic decreases in
P-32-GTP surface binding sites and in the frequency of GTP-induced dep
olarizations but no changes in H-3-lysozyme binding or lysozyme-induce
d backward swimming. These results suggest that lysozyme and GTP have
separate high affinity surface receptors on the somatic membrane that
are specifically down regulated during chemosensory adaptation. (C) 19
97 Elsevier Science Inc.