Further Studies on the Degeneration of Monoamine Nerves in the Venus Clam Heart Induced by Neurotoxic Drugs: Effects of 5,7-Dihydroxytryptamine (5,7-DHT)

Summary

The long term effects of 5.7-DHT on nerves in the Venus clam heart were studied to elucidate further the structure of serotoneragic nerves detected earlier.

At least 2 types of monoaminergic nerves with dense-cored vesicles were susceptible to significant degeneration by the drug, Among these were profiles with large granular vesicles (64–200 mn) which resemble possible serotonergic nerves seen in myenteric plexus and ’catch’ muscle of Mytilus. The other nerves lesioned were those with small granular vesicles (32–64 mn) conforming to adrenergic nerves in vertebrates. A third type of profile with a population of medium·sized. dense-cored vesicles (40–160 nm) was found to be reactive and less susceptible to degeneration,

Nerves with a predominance of small agranular vesicles and large opaque vesicles were unaffected by the drug. These resemble vertebrate cholinergic and "purinergic" nerves, respectively.

The results confirm our previous studies on the molluscan heart with neurotoxic drugs.

Key words:

• Venus clam heart
• Katelysia rhytiphora (Mollusca)
• 5.7·Dihydroxytryptamine
• 5-Hydroxytryptamine
• Dopamine
• Electron
• microscopy