Journal of Neuroscience, Vol 9, 3946-3954, Copyright © 1989 by Society for Neuroscience
A role for cGMP during tetanus toxin blockade of acetylcholine release in the rat pheochromocytoma (PC12) cell line
K Sandberg, CJ Berry, E Eugster and TB Rogers
Department of Biological Chemistry, University of Maryland School of Medicine, Baltimore 21201.
In order to identify the specific molecular mechanisms involved in
neurosecretion, we investigated the mechanism of action of tetanus toxin, a
potent presynaptic neurotoxin, in the rat adrenal pheochromocytoma PC12
cell line. It has recently been reported that tetanus toxin is a potent
inhibitor of the release of depolarization- evoked 3H-acetylcholine (ACh)
from nerve growth factor-differentiated PC12 cells (Sandberg et al.,
1989a). In PC12 cells, as in many neural tissue preparations, cGMP
accumulation in intact cells increased 6- to 17-fold when stimulated with
veratridine (200 microM), carbachol (1 mM), Ba2+ (2 mM), or K+ (30 mM).
Preincubation of the cells with tetanus toxin inhibits this accumulation by
greater than 95%. The toxin dose-inhibition curves for 3H-ACh release and
cGMP accumulation are similar, with half-maximal doses of tetanus toxin
seen at approximately 5 nM. The time courses for the development of the
effects of tetanus on 3H-ACh release and on cGMP accumulation were also
similar. Protocols which elevated intracellular cGMP levels reversed the
action of the toxin. For example, evoked ACh release was restored in
intoxicated PC12 cells by a 15 min exposure to 100 microM 8-bromo-cGMP. The
half-maximal dose was observed at 50 microM nucleotide. Examination of the
nucleotide specificity revealed that only cyclic guanine analogs were
effective in reversing the effects of tetanus toxin. These results
suggested that the inhibition of depolarization-evoked cGMP accumulation is
causally related to the action of tetanus toxin on neurosecretion.(ABSTRACT
TRUNCATED AT 250 WORDS)