PT  - JOURNAL ARTICLE
AU  - Cornelis E. Koert
AU  - Gaynor E. Spencer
AU  - Jan van Minnen
AU  - Ka Wan Li
AU  - Wijnand P. M. Geraerts
AU  - Naweed I. Syed
AU  - August B. Smit
AU  - Ronald E. van Kesteren
TI  - Functional Implications of Neurotransmitter Expression during Axonal Regeneration: Serotonin, But Not Peptides, Auto-Regulate Axon Growth of an Identified Central Neuron
AID  - 10.1523/JNEUROSCI.21-15-05597.2001
DP  - 2001 Aug 01
TA  - The Journal of Neuroscience
PG  - 5597--5606
VI  - 21
IP  - 15
4099  - http://www.jneurosci.org/content/21/15/5597.short
4100  - http://www.jneurosci.org/content/21/15/5597.full
SO  - J. Neurosci.2001 Aug 01; 21
AB  - We studied the regenerative properties of one of two electrically coupled molluscan neurons, the serotonergic cerebral giant cells (CGCs) of Lymnaea stagnalis, after axotomy. The CGCs play a crucial role in feeding behavior, and when both cells are disconnected from their target neurons, animals no longer feed. When one CGC was permanently disconnected from its targets and the other was reversibly damaged by a nerve crush, the latter one regenerated over a period of 2 weeks to reform functional synapses with specific target neurons. At the same time, recovery of the feeding behavior was observed. After the crush, neuropeptide gene expression in the CGC was downregulated to ∼50%. Serotonin synthesis, on the other hand, remained unaffected, suggesting that serotonin might have an active role in regeneration. In primary neuron culture, CGCs failed to extend neurites in the presence of serotonin; in cells that extended neurites in the absence of serotonin, focally applied serotonin, but not neuropeptides, induced growth cone collapse. Using serotonin-sensitive sniffer cells, we show that CGC neurites and growth cones release serotonin in culture. Finally, both the spontaneous and stimulation-induced release of serotonin from CGCs in culture resulted in growth cone collapse responses that could be blocked by the serotonin receptor antagonist methysergide. Our data suggest that auto-released serotonin is inhibitory to CGC neurite outgrowth in vitro. During regeneration in vivo, serotonin release might fine-tune axon guidance and branching by inducing local collapse responses in extending neurites.