Unexpected plasticity at autonomic junctions. Environmental regulation of neurotransmitter phenotype and receptor expression

Development of neuropeptide Y immunoreactive amacrine and ganglion cells in the pre- and postnatal cat retina

In the adult cat, neuropeptide Y (NPY) immunoreactivity (IR) is found within a subgroup of gamma-type ganglion cells and a large group of regularly arrayed amacrine cells. To examine the development of these two cell groups, we charted the appearance and maturation of neuropeptide Y immunoreactivity in the pre- and post-natal cat retina. Neuropeptide Y immunoreactivity is first observed at the central retina within the ganglion cell layer on embryonic day 46, and immunoreactivity within amacrine cells of the inner plexiform layer is present by E50. The number of immunoreactive profiles reaches the adult level in the amacrine population first (around P7), while the ganglion cell population shows a protracted development, with new cells being added until the third postnatal week. NPY-immunoreactive profiles in the ganglion cell layer were confirmed to be ganglion cells by retrograde labeling in both pre- and post-natal animals. Thus, neuropeptide Y-immunoreactive ganglion cells and amacrine cells attain their mature state with very different timecourses, although both cell groups initially follow a central to peripheral pattern of development. Interestingly, NPY expression within the ganglion cell population is temporally correlated with retinal synaptogenesis in the inner plexiform layer. As in the adult cat, NPY-immunoreactive ganglion cells never show a regular distribution during development, while NPY-IR amacrine cells are always distributed regularly even at the earliest ages. The prenatal presence of a regular distribution of NPY-IR amacrine cells suggests that these cells may participate in establishing the ganglion cell mosaics that appear during postnatal development.

Cell density regulates neuropeptide Y expression in cultured sympathetic neurons

Neurotransmitters and neuropeptides coexpressed by the same neuron may be regulated independently. The peptide transmitter, neuropeptide Y (NPY), has been identified in approximately 60% of rat sympathetic superior cervical ganglion (SCG) neurons, virtually all of which are catecholaminergic. However, we find that environmental signals which affect noradrenergic traits in cultured rat SCG, regulate NPY expression differently. Relatively large increases in neuronal density only slightly alter catecholaminergic properties in sympathetic neurons. However, levels of NPY were highly dependent on cell density. In pure neuronal cultures, increasing cell numbers from 8000 to 12,000 neurons per culture resulted in a 10-fold decrease in NPY. Coculture of SCG neurons with ganglion nonneuronal cells further reduced NPY levels at all neuronal densities examined. Treatment with the neuropoetic cytokine, leukemia inhibitory factor, which increased the expression of cholinergic traits and decreased noradrenergic expression, decreased NPY by 50% in cocultures. Finally, neither glucocorticoids nor the cytokine interleukin-1 beta, which regulate other transmitter systems, altered NPY expression. These observations indicate that although noradrenergic traits and NPY are often coexpressed, they are regulated independently in SCG neurons. Further, expression of NPY is highly influenced by cell-cell contact.

Functional disturbances of the autonomic nerve in nasal hyperreactivity: an up-date review

During the 1980s, our view of airway hypersensitivity was altered significantly. Advances in biochemical techniques revealed involvement of several nonspecific events in nasal hyperreactivity: Autonomic dysfunction involving primary and/or secondary receptor disorders, epithelial damage by cytotoxic proteins in eosinophil, which is stimulated by inflammatory mediators, and an axonal reflex of sensory C fibers. Since 1983, we have neurobiochemically investigated the autonomic nerve dysfunction in the nasal mucosa of patients with nasal allergy and guinea pigs with experimentally-induced nasal hypersensitivity. We propose the following mechanisms as potential contributors to the disturbance of the beta receptor function in airway hyperreactivity: i) Down-regulation caused by excess endogenous norepinephrine stimulation, ii) down-regulation and uncoupling to adenylate cyclase, produced by the inflammatory mediator-induced activation of protein kinase C, iii) the action of beta receptor inhibitory factor, presumably anti beta receptor autoantibodies, and iv) dysfunction of beta receptor kinase, which is known to cause short-term desensitization of beta receptors after exposure to beta agonists. This review provides the anatomical and neurobiochemical background for the autonomic regulation and dysfunction in the nose. We also introduce our series of experiments and the above updated hypotheses of how functional disturbances of the autonomic nerve in the nasal mucosa may occur.