[Effect of cerebral intraventricular administration of 5,6-dihydroxytryptamine and 5,7-dihydroxytryptamine on the cyclic secretion of corticosterone in the rat].

The effect of two potent neurotoxic agents for 5HT neurons, 5,6-DHT and 5,7-DHT, intraventricularly injected, has been studied on the values and rhythm of plasmatic corticosterone secretion in the male Wistar rat model, along an entire day: 4 a.m., 8 a.m., noon, 5 p.m. and midnight. The dose administered for each drug was 100 micrograms/animal in a single injection. The levels of corticosterone were determined 15 and 30 days post-injection. The effects observed for both drugs were similar at similar times: highly significant decreases in all the studied points which fall under the same line of secretion and evince an absolute inhibition of the cyclic rhythm. There are no significant differences among the values obtained with different drugs at various times. The contents of NA and 5HT significantly decrease for both drugs especially those of the 5HT on the 15th day. 30 days after the injection there is a small recovery of 5HT, but differences with control values are still significant. On the other hand the recovery of NA was almost total (near 100%). The results are discussed within the highly controversial frame of the influence of central 5HT neurons on the various types of secretion of the hypothalamic-pituitary-adrenal axis. The data obtained with this "chronic model" are confronted with those from other authors who have used drugs with transitory effect on the 5HT brain metabolism.