Electrophysiological and cyclic AMP responses to beta-adrenergic receptor stimulation and catecholamine levels in cat and rabbit sympathetic ganglion

Localization, regulation and functions of neurotransmitters and neuromodulators in cervical sympathetic ganglia

Cervical sympathetic ganglia represent a suitable model for studying the establishment and plasticity of neurochemical organization in the nervous system since sympathetic postganglionic neurons: (1) express several neuromediators, i.e., short acting transmitters, neuropeptide modulators and radicals, in different combinations; (2) receive synaptic input from a limited number of morphologically and neurochemically well-defined neuron populations in the central and peripheral nervous systems (anterograde influence on phenotype); (3) can be classified morphologically and neurochemically by the target they innervate (retrograde influence on phenotype); (4) regenerate readily, making it possible to study changes in neuromediator content after axonal lesion and their possible influence on peripheral nerve regeneration; (5) can be maintained 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) paravertebral ganglia. Furthermore, mechanisms regulating transmitter synthesis in sympathetic neurons in vivo and in vitro, such as soluble factors, cell contact or electrical activity, are summarized, since modulation of transmitter synthesis, release and metabolism plays a key role in the neuronal response to environmental influences.

Actions of vasoactive intestinal polypeptide in superior cervical ganglion of the cat

Effects of vasoactive intestinal polypeptide (VIP) in the superior cervical ganglion (SCG) of the cat were investigated in situ. Vasoactive intestinal polypeptide (0.075-1.5 nmol) induced a dose-dependent depolarization of the superior cervical ganglion, characterized by a long-latency, slow onset, small amplitude and long duration. Initial short-lasting hyperpolarization of the superior cervical ganglion was observed in 5 out of 8 experiments after administration of VIP in a dose of 0.75 nmol. Vasoactive intestinal polypeptide (0.075-1.5 nmol) unmasked the muscarinic slow negative potential, following the compound action potential and unmasked or enhanced the stimulus-bound decremental oscillatory potentials induced by the muscarinic agonist McN-A-343 in the superior cervical ganglion. Vasoactive intestinal peptide induced a slight, but significant increase in the amplitude of the postganglionic action potentials evoked by preganglionic stimulation. The data mentioned above suggest that VIP may act as a neuromodulator of cholinergic transmission at the ganglionic synapse.

Depolarization and muscarinic excitation induced in a sympathetic ganglion by vasoactive intestinal polypeptide

The effects of vasoactive intestinal polypeptide (VIP) in the superior cervical ganglion of the cat were studied in vitro and in vivo with sucrose gap and multiunit recording, respectively. At a dose of 0.03 to 0.12 nanomole, VIP produced a dose-dependent, prolonged (3 to 15 minutes) depolarization of the ganglion and enhanced the ganglionic depolarization elicited by the muscarinic agonist acetyl-beta-methylcholine. At a dose of 1.8 to 10 nanomoles, the peptide enhanced and prolonged the postganglionic discharge elicited by acetyl-beta-methylcholine, enhanced muscarinic transmission in ganglia treated with an anticholinesterase agent, and enhanced the late muscarinic discharge elicited by acetylcholine. VIP did not affect the early nicotinic discharge elicited by acetylcholine or by electrical stimulation of the preganglionic nerve. It is concluded that VIP has a selective facilitatory action on muscarinic excitatory mechanisms in the superior cervical ganglion of the cat.