ISSN:
1432-1912
Keywords:
B-HT 920
;
B-HT 933
;
B-HT 958
;
Presynaptic α2-auto-receptor
;
Noradrenaline release
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The effects of the three azepine compounds, B-HT 920 (6-allyl-2-amino-5,6,7,8-tetrahydro-4H-thiazolo-[4,5-d]azepine), B-HT 933 [2-amino-6-ethyl-5, 6, 7, 8-tetrahydro-4H-oxazolo [4,5-d]azepine; azepexole] and B-HT 958 (2-amino-6-(p-chloro-benzyl)-4H-5, 6, 7, 8-tetrahydrothiazolo[5,4-d]azepine) on electrically evoked overflow of 3H-noradrenaline were studied. Slices from parietal cortex (Cξ) or nucleus anterior hypothalami (nah) were incubated with 3H-noradrenaline, superfused at 23°C or 37°C in the presence of the noradrenaline uptake inhibitor desipramine (3 μmol/l) and field stimulated at frequencies of 0.3 or 3 Hz. 1. At 37°C/0.3 Hz, B-HT 920 and B-HT 933 concentration-dependently decreased the evoked overflow of tritium in both regions studied, whereas B-HT 958 had no effect. 2. In a second set of experiments each drug was tested under three additional experimental conditions, i. e. 37°C/3 Hz, 23°C/ 0.3 Hz and 23°C/3 Hz. Increasing the stimulation frequency to 3 Hz or lowering the superfusion temperature to 23°C reduced the effects of B-HT 920 (1 μmol/l) and B-HT 933 (10 μmol/l) as compared to the effects at 37°C/0.3 Hz. When tested at 23°C/3 Hz, both drugs did not significantly affect the evoked overflow of tritium in the Cx or the nah. In contrast, B-HT 958 (10 μmol/l), caused a facilitation of evoked overflow in both regions when the higher stimulation frequency or the lower superfusion temperature was used. Its release-enhancing action was most pronounced at 23°C/3 Hz. 3. Idazoxan (0.1 μmol/l) antagonized the effects of BHT 920 (10 μmol/l) and B-HT 933 (10 gmmol/l) in the Cx at 37°C/0.3 Hz. The ineffectiveness of B-HT 958 under these experimental conditions was not changed in the presence of idazoxan. Sulpiride (10 μmol/l) did not affect the action of any of the three compounds. 4. From the patterns of effects obtained under the different experimental conditions it is concluded that B-HT 920 and B-HT 933 act as agonists at prejunctional α2-adrenoceptors, whereas B-HT 958 acts as a weak antagonist at these sites. Send offprint requests to E. A. Singer at the above address
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00166976
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