ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: Substance P (SP), the widely distributed undeca-peptide, is synthesized in cell bodies of vagal sensory ganglia and transported bidirectionally toward the CNS and thoracic and abdominal viscera. In explants of the guinea pig inferior (nodose) vagal sensory ganglion and attached 2 cm of distal vagus nerve, SP is synthesized within the ganglion and transported predominantly distally. The quantity of distal transport is similar to that observed in vivo and provides an index of ongoing synthesis within the ganglion. In this report, the model is further characterized. Double ligation of the explant distal to the ganglion demonstrates that all the transported peptide is derived from the ganglion; there is no evidence of intraaxonal processing of peptide precursor. Approximately 50% of the peptide is in a rapid transport vs. an apparent stationary compartment. Not only transport, but also synthesis, of SP was blocked by 20 mM colchicine. Ongoing SP biosynthesis is dependent on a nutrient medium [medium 199 (M-199)] and is partially inhibited with added fetal bovine serum (FBS; 10%): total ex-plant content in M-199/FBS vs. M-199, 1, 785 ± 101 (n = 8) vs. 2, 254 ± 123 pg (n = 9); p 〈 0.02. Addition of 2-deoxyglucose (2-DG) decreased both total SP synthesis and transport (total explant content for 2-DG vs. control, 986 ± 94 vs. 1, 391 ± 111; p 〈 0.05). Medium supplemented with glucose to a final concentration of 600 mg/100 ml or with glucose (300 mg/100 ml) with or without insulin (50 ng/ml) did not alter explant SP content or transport. Veratridine (5 ± 10−−6M) inhibited both SP synthesis and transport; ouabain (10−−4M) also inhibited synthesis, but less so transport. Tetrodo-toxin reversed the effects of veratridine. These studies demonstrate the usefulness of this model, which can examine factors regulating both synthesis and transport of sensory neuropeptides in vitro. The results suggest that SP synthesis/transport may be under tonic inhibition, perhaps by both neural and humoral mechanisms.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1987.tb05738.x
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