Estimates of total spontaneous input to the CNS
| Type of neuron | Firing rate per neuron | Calculated no. SD and LL neurons | % NOCIS with SA | Calculated total | |||
|---|---|---|---|---|---|---|---|
| Median (Hz) | Mean (Hz) | Total | NOCIS | No. NOCIS with SA | Spinal cord input (Hz) | ||
| Nerve injury | |||||||
| C-NOCIS mSNA L4 | 1.8 | 1.9 | 8400 SD | 7560 | 35 | 2646 | 5027 |
| C-NOCIS SNA L4 | 0.017 | 0.24 | 8400 SD | 7560 | 35 | 2646 | 635 |
| A-NOCIS mSNA L4 | 0.01 | 0.035 | 3600 LL | 828 | 10.3 | 85 | 3 |
| A-NOCIS SNA L4 | 0.035 | 0.17 | 3600 LL | 828 | 14.3 | 118 | 20 |
| CFA-induced inflammation | |||||||
| CFA1 L4 + L5 | 0.5 | 0.59 | 21, 000 SD | 18, 900 | 38 | 7182 | 4237 |
| CFA4 L4 + L5 | 0.1 | 0.15 | 21, 000 SD | 18, 900 | 25 | 4725 | 709 |
| a | b | c | d | e = c × d | f = a × e | ||
For SNA and mSNA rats, the spontaneous firing rate was counted in individual L4 nociceptive neurons with SA (see Results). For CFA rats, calculations are for L4 and L5, because both DRGs project to the inflamed hindlimb. The mean firing rate (a) (not the median) was used as the appropriate variable for estimating total firing rate. The derivation of the numbers is described in detail in Results. The calculated total numbers of neurons (columns b and c) are derived from published data. The “% NOCIS with SA” (d) was measured in this study. The calculated totals of neuronal activity are derived as shown in e and f. N.B., Although these are estimates, we have kept exact numerical values to make calculations easier to follow. SD, Small dark neurons that have C-fibers; LL, large light neurons that have A-fibers (Harper and Lawson, 1985); NOCIS, nociceptive-type neurons.