Table 2.
Properties of electrically evoked overflow of tritium in rat and human neocortical slices preincubated with either [3H]-NA: effects of Ca2+-free medium, tetrodotoxin and α2-adrenoceptor agonists and antagonists
| Drug before Sn | Rat neocortex | Human neocortex |
|---|---|---|
| Ca2+-free medium |
ND |
15.28±4.61 (n=5)*** |
| Tetrodotoxin (0.3 μM) |
ND |
9.84±3.08 (n=5)*** |
| UK-14,304 (0. 1 μM) |
13.40±1.47 (n=5)*** |
11.06±3.430 (n=3)*** |
| Idazoxan (1 μM) |
106.66±1.30 (n=6) |
96.59±2.94 (n=8) |
| UK-14,304 (0.1 μM) (idazoxan, 1 μM, throughout) | 98.92±1.81 (n=5)+++ | 55.6±11.07 (n=3)***,+++ |
Rat or human neocortical slices were preincubated with [3H]-NA and then superfused continuously in the presence of desipramine (1 μM); in addition to desipramine, idazoxan (1 μM) was present throughout superfusion in part of the experiments. Overflow of tritium was evoked up to three times (S1–S3) by electrical fields using the following conditions: 4 (rat neocortex), or 8 (human neocortex) pulses at 100 Hz, 2 ms, 34 mA (for tissue accumulation of [3H]-NA and the evoked overflow of [3H] at S1 see Table 1). Drugs to be tested were added to the superfusion medium from 8 min before Sn onwards, their effects are expressed in % of the corresponding controls (no drug addition before Sn). Statistics:
P<0.001 vs controls;
P<0.001 vs UK-14,304 alone; ND, not determined, but see discussion.