Complement-mediated lesion of sympathetic ganglia in vitro with acetylcholinesterase antibodies

When administered to rats, antibodies against acetylcholinesterase (AChE) selectively destroy presynaptic inputs to sympathetic ganglia. To investigate the mechanism of this immunolesion, we created an in vitro system in which relevant components could be manipulated. Freshly dissected rat superior cervical ganglia (SCG) were incubated 15-20 h at 37°C in fresh human serum (a potent source of complement) with continuous oxygenation. More than 96% of neurons in six control ganglia retained synaptic inputs, as defined by action potentials or excitatory postsynaptic potentials (EPSP) upon stimulation of the preganglionic trunk. However, when anti-AChE antibodies were present (0.16 mg/ml), none of 61 neurons from six incubated ganglia showed synaptic responses although membrane potential and input resistance remained normal. Staining for AChE and synaptophysin (a synaptic vesicle marker) was also disrupted in ganglia exposed to AChE antibodies in complement-sufficient serum. When complement was eliminated by substituting serum that was heat-inactivated or deficient in C3, synaptic input was retained in 60-90% of neurons incubated with AChE antibodies. Choline acetyltransferase activity (ChAT), an enzymatic marker of cholinergic cytoplasm in sympathetic ganglia, was largely lost after incubation with AChE antibodies and serum. However, incubation with AChE antibodies in heat-inactivated serum, or serum that was deficient in C3 or C8, caused no measurable loss of ganglionic ChAT activity. These findings strongly implicate the complement cascade in the destruction of preganglionic sympathetic terminals that follows binding of AChE antibodies.