PREGANGLIONIC SYMPATHETIC NEURONS, INNERVATING THE GUINEA-PIG ADRENAL-MEDULLA, IMMUNOHISTOCHEMICALLY CONTAIN CHOLINE-ACETYLTRANSFERASE AND ALSO LEU-ENKEPHALIN

Applying retrograde neuronal tracing combined with double labelling im munofluorescence, preganglionic nerve cell bodies in the intermediate grey matter of the guinea pig thoracic spinal cord, projecting to the adrenal gland, co-exhibited immunolabelling for choline-acetyltransfer ase (ChAT) and sometimes, also for leu-enkephalin. Likewise, ChAT-immu noreactive nerve fibres, forming a dense meshwork in the adrenal medul la, partly contained immunostaining also for leu-enkephalin. Some of t he intramedullary nerve cell bodies were ChAT-positive but were non-re active for leu-enkephalin. The findings provide evidence for an extrin sic (preganglionic) and an intrinsic (postganglionic) cholinergic nerv e system in the guinea pig adrenal medulla, the preganglionic system u tilising leu-enkephalin as co-mediator.