Ultrastructural organization of regenerated serotonin axons in the dorsomedial hypothalamus of the adult rat

J Neurocytol. 1987 Dec;16(6):799-809. doi: 10.1007/BF01611987.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 5,7-Dihydroxytryptamine / pharmacology
  • Animals
  • Autoradiography
  • Axons / analysis*
  • Axons / ultrastructure
  • Hypothalamus / analysis*
  • Hypothalamus / ultrastructure
  • Male
  • Nerve Regeneration*
  • Rats
  • Rats, Inbred Strains
  • Serotonin / analysis*


  • 5,7-Dihydroxytryptamine
  • Serotonin