General properties of caudal raphe neurons
| Effect of 5-HT, mV | TPH Immunopositive (34) | TPH Immunonegative (17) | ||
|---|---|---|---|---|
| Hyperpolarization (−13.8 ± 1.6) | No effect | Hyperpolarization (−13.7 ± 1.5) | Depolarization (+11.8 ± 2.6) | |
| Number of cells | 32 | 2 | 9 | 7 |
| Cell capacitance, pF | 26.6 ± 0.9 (26) | 25; 17 | 25.3 ± 1.6 (9) | 23.2 ± 0.4 (5) |
| Input resistance, GΩ | 1.6 ± 0.2 (22) | 1.0; 1.3 | 1.2 ± 0.2 (8) | 0.9 ± 0.1 (6) |
| Membrane potential, mV | −49.7 ± 1.0 (31) | −46.0; −46.0 | −45.7 ± 1.6 (9) | −57.2 ± 0.7* (6) |
| Spontaneous firing, Hz | 1.3 ± 0.2 (24) | 1.0 (1) | 1.7 ± 0.3 (5) | 0.0 ± 0.0 (6) |
| Spike duration, ms | 5.5 ± 0.3 (28) | 5; 6 | 5.4 ± 0.7 (8) | 3.3 ± 0.2* (6) |
-
Values in Hyperpolarization and Depolarization are means ± SE. Numbers in parentheses: number of cells measured for each parameter. All recordings were made in 3 mM K+. Top row: effect of 5-HT (1–5 μM) on membrane potential. Second row: number of cells in each group recovered after histological processing. Fifth row: in spontaneously active cells, membrane potential was taken as the midpoint between the peak of the afterhyperpolarization and the action potential threshold. The 1 tryptophan hydroxylase (TPH)-immunonegative cell that did not respond to serotonin (5-HT) was excluded from the remainder of this table.
-
↵* Significantly different from all other groups.