A novel calmodulin antagonist, CGS 9343B, modulates calcium-dependent changes in neurite outgrowth and growth cone movements.
The neurotransmitter 5-HT alters growth cone motility and neurite elongation in neuron B19, isolated from the buccal ganglion of Helisoma trivolvis (Haydon et al., 1984). The effects of 5-HT are mediated by increases in intracellular calcium levels within the growth cones (Cohan et al., 1987). 5-HT causes a receptor-mediated depolarization of the membrane, which results in the opening of voltage-sensitive calcium channels. The resulting calcium influx decreases both the elongation rate and the total outgrowth of neurites. However, the mechanism(s) mediating these calcium-dependent changes is unclear. As many of the intracellular effects of calcium in eukaryotic cells are mediated by the calcium-binding protein calmodulin, we tested the involvement of such an interaction in the regulation of neurite outgrowth. In these experiments, a new, potent calmodulin antagonist with increased selectivity, CGS 9343B (CGS; Norman et al., 1987), was used to inhibit calmodulin activity during the application of 5-HT to neuron B19. The addition of 100 microM 5-HT to the culture medium resulted in a significant decrease in the rate of neurite elongation and total neurite outgrowth. Administration of CGS to the culture medium at a concentration (1.8 microM) equivalent to its IC50 for calmodulin inhibition completely blocked the inhibitory effects of 100 microM 5-HT, on both neurite elongation and total neurite outgrowth. CGS alone caused a slight decrease in elongation rate but had no significant effect on total outgrowth. CGS did not block 5-HT-induced electrical activity, indicating that it was not acting as a 5-HT receptor antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)
Polak
K A
KA
Department of Pharmacology, School of Medicine and Biomedical Sciences, State University of New York, Buffalo 14214.
Edelman
A M
AM
Wasley
J W
JW
Cohan
C S
CS
D000818:Animals; D001369:Axons / Q000502:physiology*; D001562:Benzimidazoles / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology*; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D002465:Cell Movement; D004594:Electrophysiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology; D012908:Snails; D013449:Sulfonamides / Q000494:pharmacology; D014268:Trifluoperazine / Q000494:pharmacology
D001562:Benzimidazoles; D002147:Calmodulin; D013449:Sulfonamides; C052087:CGS 9343B; D014268:Trifluoperazine; D012701:Serotonin; C017967:W 7; D002118:Calcium