Effects of neonatal treatment with 5,7-dihydroxytryptamine or 6-hydroxydopamine on the ontogenetic development of the audiogenic immobility reaction in the rat

✍ Scribed by Ernest Hård; Sven Ahlenius; Jörgen Engel

• Publisher: Springer
• Year: 1983
• Tongue: English
• Weight: 722 KB
• Volume: 80
• Category: Article
• ISSN: 0033-3158
• DOI: 10.1007/bf00436168

✦ Synopsis

The ontogenetic development of the audiogenic immobility reaction (freezing) was studied in rats given intracisternal injections of the neurotoxins 5,7-dihydroxytryptamine (5,7-DHT), 25 gg, or 6-hydroxydopamine (6-OHDA), 100 gg, neonatally (Day 1). The duration of the freezing response was strongly reduced in the 5,7-DHTtreated rats between 20" 30 days of age, when normal animals show very prolonged responses. During the same period increased motor activity was observed in the 6-OHDA-treated rats while only a slight reduction of the freezing response was noted. Biochemical analyses performed on brains from animals 35 days of age showed a selective reduction (about 50 %) of whole brain levels of serotonin in the 5,7-DHT-treated rats, while the noradrenaline levels were selectively reduced by about 60 % in the 6-OHDA rats. A longitudinal investigation on the effects of neonatal treatment with 5,7-DHT showed a persistent selective reduction of the whole brain level of serotonin up to at least 90 days of age. Since 5,7-DHT mainly affects the serotonergic pathways, the results suggest that the disturbances noted in the ontogeny of the freezing response may be due to interference with the developing serotonergic system.