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The effect of the selective 5-HT1A agonists alnespirone (S-20499) and 8-OH-DPAT on extracellular 5-hydroxytryptamine in different regions of rat brain
|Autor:||Casanovas, Josep M.; Lesourd, Monique; Artigas, Francesc|
|Palabras clave:||5-Hydroxytryptamine (5-HT) release|
Dorsal raphe nucleus
Median raphe nucleus
|Fecha de publicación:||oct-1997|
|Editor:||British Pharmacological Society|
|Citación:||British Journal of Pharmacology 122(4): 733–741 (1997)|
|Resumen:||1. We have examined the effects of the systemic administration of the selective 5-HT1A agonist alnespirone (S-20499) on in vivo 5-hydroxytryptamine (5-HT) release in the dorsal raphe nucleus, the median raphe nucleus and four forebrain areas innervated differentially by both (dorsal striatum, frontal cortex, ventral hippocampus and dorsal hippocampus).|
2. Alnespirone (0.1–3mgkg−1, s.c.) dose-dependently reduced extracellular 5-HT in the six areas examined. In forebrain, the maximal reductions occurred in striatum and frontal cortex (maximal reduction to 23 and 29% of baseline, respectively). Those in dorsal and ventral hippocampus were more moderate (to ca 65% of baseline). In contrast, the decrease in 5-HT elicited in the median raphe nucleus was more marked than that in the dorsal raphe nucleus (to ca 30 and 60% of baseline, respectively). The selective 5-HT1A antagonist WAY-100635 (0.5mgkg−1, s.c.) prevented the decrease in 5-HT induced by alnespirone (0.3mgkg−1, s.c.) in frontal cortex.
3. 8-OH-DPAT (0.025, 0.1 and 0.3mgkg−1, s.c.) also reduced extracellular 5-HT in a regionally-selective manner (e.g., to 32% of baseline in striatum and to 69% in dorsal hippocampus at 0.1mgkg−1, s.c.). In midbrain, 8-OH-DPAT reduced the dialysate 5-HT slightly more in the median than in the dorsal raphe nucleus at all doses examined.
4. Doses of both compounds close to their respective ED50 values (0.3mgkg−1 alnespirone, 0.025mgkg−1 8-OH-DPAT) reduced 5-HT to a comparable extent in all regions examined. However, the reductions attained at higher doses were more pronounced for 8-OH-DPAT.
5. These data show that the reduction of 5-HT release elicited by alnespirone and 8-OH-DPAT is more important in forebrain areas innervated by 5-hydroxytryptaminergic neurones of the dorsal raphe nucleus. This regional selectivity seems unlikely to be accounted for by differences in the sensitivity of 5-HT1A autoreceptors controlling 5-HT release, given the dissimilar effects of these two 5-HT1A agonists in regions rich in cell bodies and nerve terminals. This suggests the presence of complex mechanisms of control of 5-HT release by 5-HT1A receptors.
|Versión del editor:||http://dx.doi.org/10.1038/sj.bjp.0701420|
|Aparece en las colecciones:||(IIBB) Artículos|
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