Table 1.
Effectiveness of various dopaminergic agonists in eliciting conductance changes in island of Calleja granule cells
| Agonist | Latency (min) | Vrev,min (mV) | Vrev,max (mV) | Initial conductance (pS) | Maximal conductance (nS) | Increase (%) | n |
|---|---|---|---|---|---|---|---|
| Dopamine (300 nm) | 7·9 ± 2 * | -32·7 ± 4·5 | -6·3 ± 0·9 | 241 ± 47 | 6·48 ± 3·5 | 2589 | 3 |
| Apomorphine (10-300 nm) | 6·1 ± 0·9 | -36·3 ± 4·3 | -5·8 ± 4·0 † | 533 ± 101 | 5·66 ± 1·8 | 1271 | 8 |
| Quinpirole (100 nm)§ | 6·6 ± 1·1 | -32·0 ± 4·1 | -6·2 ± 2·3‡ | 592 ± 141 | 11·81 ± 3·37 | 3202 | 5 |
| 7-OH DPAT (100-300 nm)§ | 7·7 ± 0·73 | -42 ± 13 | 2·7 ± 4·8 | 280 ± 27 | 5·5 ± 1·6 | 1693 | 3 |
| PD 128907 (300 nm)§ | 6·0 ± 0·8 | -26·0 ± 4·3 | -4·6 ± 1·4¶ | 305 ± 43 | 8·25 ± 1·93 | 3083 | 5 |
The latency was the time between switching to agonist containing ACSF and the onset of the ‘cataclysmic’ component - the large inward current and conductance increase observed at -80 mV.
The value for dopamine was derived from current-clamp observations (n = 7); the remainder from voltage-clamp experiments. Reversal potentials at the start of responding (the minimal component; Vrev,min) and at the peak of inward current (Vrev,max) were determined from intersections of extrapolated I-V curves as indicated in Fig. 5. Neuronal input conductance prior to agonist application (initial conductance) and at the peak inward current (maximal conductance) were determined by the slopes of I-V relations between -70 and -100 mV also as indicated in Fig. 5.
Experimental series undertaken in ACSF that contained 1 mm Ba2+ Paired t tests were employed to test for differences in Vrev,min and Vrev,max and yielded exact probabilities of P = 0·013
for apomorphine, P = 0·016
for quinpirole and P = 0·021
for PD 128907.