Ultrastructural organization of regenerated serotonin axons in the dorsomedial hypothalamus of the adult rat.
The ultrastructural organization of regenerated serotonin (5-HT) axons was examined in the dorsomedial hypothalamus (DMH) of the adult rat using high-resolution radioautography after intraventricular infusion of [3H]5-HT. An analysis of the microenvironment of the [3H]5-HT-labelled terminals in the DMH was made 30 and 50 days after unilateral injection of 5,7-dihydroxytryptamine (5,7-DHT) or vehicle solution into the dorsolateral hypothalamus. In sham-treated animals [3H]5-HT-labelled axons were small, contained many small clear vesicles, one or more large granular vesicles, and showed only rare synaptic specializations. In 5,7-DHT-treated animals the internal organization of [3H]5-HT-labelled profiles resembled that of sham-treated animals. A tendency toward increased synaptic frequency was found for [3H]5-HT-labelled terminals in the 5,7-DHT-treated group 50 days post-lesion, and an increase in the number of [3H]5-HT-labelled terminals abutting unlabelled perikarya was found in both 30- and 50-day post-lesion groups as compared to sham-treated groups. No other differences in ultrastructural environment were found between sham- and 5,7-DHT-treated animals at either 30 or 50 days post-lesion. These results suggest that 5-HT fibres in the hypothalamus regenerate with a great deal of cellular specificity.
Frankfurt
M
M
Neuroanatomy Laboratory, Montreal Neurological Institute, Quebec, Canada.
Beaudet
A
A
D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D001369:Axons / Q000032:analysis* / Q000648:ultrastructure; D007031:Hypothalamus / Q000032:analysis* / Q000648:ultrastructure; D008297:Male; D009416:Nerve Regeneration; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000032:analysis*
D015116:5,7-Dihydroxytryptamine; D012701:Serotonin