Effects of synthesis inhibition and nervous activity on concentrations of neuronal substance P.

1. When dorsal root ganglia were incubated in vitro with a range of concentrations of anisomycin, incorporation of [ 3H ]lysine into protein and synthesis of substance P(SP) were inhibited to a similar extent confirming that SP is synthesised by a conventional ribosomal mechanism. 2. Doses of anisomycin sufficient to inhibit protein synthesis in mouse CNS in vivo by greater than 95% did not cause a significant fall in the SP content of any of five brain areas, spinal cord, dorsal root ganglia or cornea over an 8 h period. 3. Electrical stimulation of the hind limbs however, produced a 25% fall in the SP content of the dorsal spinal cord of these animals. 4. These findings suggest that the turnover-time of neuronal SP is much longer than that of non-peptide neurotransmitters.