Table 1.
Conduction velocities and basal discharge rates of type I-V neurons
| Neuronal type* | Group | No. | Conduction velocity† (ms−1) | Firing rate (Hz) |
|---|---|---|---|---|
| I | Total‡ | 43 | 3.1 ± 0.3 (0.47–8.8) | 11 ± 1 (0–30) |
| PNMT+ | 9 | 2.7 ± 0.9 (0.56–8.8) | 9.9 ± 2.6 (1–23) | |
| PNMT− | 5 | 4.0 ± 0.6 (2.2–5.4) | 4 ± 3 (0–15) | |
| II | Total | 15 | 0.42 ± 0.02 (0.29–0.65)§ | 2.0 ± 0.4 (0–5)§ |
| PNMT+ | 8 | 0.38 ± 0.02 (0.29–0.48) | 1.3 ± 0.4 (0–3) | |
| PNMT− | 4 | 0.49 ± 0.06 (0.39–0.65) | 1.4 ± 0.7 (0–3) | |
| III | Total | 11 | 0.35 ± 0.03 (0.22–0.52)§ | 5 ± 1 (0–19) |
| PNMT+ | 4 | 0.31 ± 0.03 (0.26–0.39) | 4.3 ± 1.7 (1–9) | |
| PNMT− | 4 | 0.31 ± 0.05 (0.22–0.39) | 5 ± 3 (0–14) | |
| IV | Total | 17 | 1.2 ± 0.2 (0.26–2.8)§ | 2 ± 1 (0–8)§ |
| PNMT+ | 1 | 0.42 | 1 | |
| PNMT− | 6 | 1.35 ± 0.42 (0.33–2.6) | 1.5 ± 1.0 (0–6) | |
| V | Total | 8 | 0.39 ± 0.04 (0.23–0.65)§ | 1.1 ± 0.4 (0–2)§ |
| PNMT+ | 1 | 0.35 | 0.25 | |
| PNMT− | 4 | 0.43 ± 0.08 (0.23–0.65) | 0.6 ± 0.4 (0–1.5) |
Type I, cells silenced by blood pressure elevation and which projected to the cord; type II, cells silenced by blood pressure elevation, virtually unaffected by nociceptive somatic stimulation, and projecting to the hypothalamus; type III, cells silenced by blood pressure elevation, vigorously activated by nociceptive stimulation and projecting to the hypothalamus; type IV, non-barosensitive cells vigorously activated by somatic stimuli and projecting to the hypothalamus; type V, cells unresponsive to any of the applied stimuli which project to the hypothalamus.
Conduction velocities of spinal axon of type I neurones and of hypothalamic axon of type II-V neurones. Values are means ± s.e.m. with ranges shown in parentheses.
Totals for each cell type include phenotypically and non-phenotypically identified neurones.
P < 0.05 compared with corresponding values for type I cells (one-way ANOVA followed by Scheffé's test).