Degeneration and regeneration in the superior cervical sympathetic ganglion after Latrodectus venom.

The effects of the venom of the spider Latrodectus mactans hasselti on the superior cervical ganglion were studied in the guinea pig. Under anaesthesia the ganglion was bathed in venom solution for 15 min. Shortly afterwards animals salivated profusely and later developed unilateral ptosis and enophthalmos. Postoperative survival times ranged from 15 min to 10 weeks. Electron microscopy showed acute swelling of preganglionic cholinergic nerve terminals, followed by degeneration with separation of synapses. Other ganglionic elements appeared to be undamaged, although after detachment of synapses the dendritic postsynaptic specializations were reduced in number. Recovery was very rapid; axon growth cones were identifiable at 18 h and synapse reformation was well established by 2 weeks. With longer survival times there was progressive restoration of normal morphology such that by 8 weeks regeneration appeared complete. These experiments indicate that the preganglionic cholinergic nerve terminals are selectively affected by Latrodectus venom and have a considerable capacity for appropriate regeneration.