LOCALIZATION, REGULATION AND FUNCTIONS OF NEUROTRANSMITTERS AND NEUROMODULATORS IN CERVICAL SYMPATHETIC-GANGLIA

Cervical sympathetic ganglia represent a suitable model for studying t he establishment and plasticity of neurochemical organization in the n ervous system since sympathetic postganglionic neurons: (1) express se veral neuromediators, i.e., short acting transmitters, neuropeptide mo dulators and radicals, in different combinations; (2) receive synaptic input from a limited number of morphologically and neurochemically we ll-defined neuron populations in the central and peripheral nervous sy stems (anterograde influence on phenotype); (3) can be classified morp hologically and neurochemically by the target they innervate (retrogra de influence on phenotype); (4) regenerate readily, making it possible to study changes in neuromediator content after axonal lesion and the ir possible influence on peripheral nerve regeneration; (5) can be mai ntained in vitro in order to investigate effects of soluble factors as well as of membrane bound molecules on neuromediator expression; and (6) are easily accessible. Acetylcholine and noradrenaline, as well as neuropeptides and the recently discovered radical, nitric oxide, are discussed with respect to their localization and possible functions in the mammalian superior cervical and cervicothoracic (stellate) parave rtebral ganglia. Furthermore, mechanisms regulating transmitter synthe sis in sympathetic neurons in vivo and in vitro, such as soluble facto rs, cell contact or electrical activity, are summarized, since modulat ion of transmitter synthesis, release and metabolism plays a key role in the neuronal response to environmental influences. (C) 1996 Wiley-L iss, Inc.