Comparison of immunohistochemical localization of [Met5]enkephalin-Arg6-Gly7-Leu8, [Met5]enkephalin, neuropeptide Y and vasoactive intestinal polypeptide in the superior cervical ganglion of the rat

Neuroendocrine secretory protein 55 (NESP55) immunoreactivity in male and female rat superior cervical ganglion and other sympathetic ganglia

Neuroendocrine secretory protein 55 (NESP55) is a soluble, acidic and heat-stable protein, belonging to the class of chromogranins. It is expressed specifically in endocrine cells and the nervous system, and is probably involved in both constitutive and regulated secretion. In the present study, we investigated the distribution of NESP55 in various rat sympathetic ganglia by immunohistochemistry. The expression of NESP55-IR was detected in a subpopulation of principal neurons in the rat SCG, which was also TH positive, and, thus, adrenergic. In the rat stellate ganglion, more than two thirds of NESP55 positive neurons were adrenergic. Colocalization of NESP55 and calcitonin gene-related peptide (CGRP) in cholinergic neurons was also observed. In the rat thoracic chain, however, the majority of NESP55 positive neurons appeared to lack TH. No detectable NESP55-IR was found in the mouse SCG. Furthermore, in the sexually dimorphic SCG, it was demonstrated that, 80% of the NESP55 positive principal neurons were also NPY positive in the male rat, while a slightly higher, but statistically significant proportion, 87%, was found in the female. Whether or not this small difference is physiologically significant is unknown. The present data provide basic knowledge about the expression of NESP55 in the sympathetic autonomic nervous system of rat, which may further our understanding of the functional significance of NESP55.

Peptidergic nerves in the eye, their source and potential pathophysiological relevance

Over the last five decades, several neuropeptides have been discovered which subsequently have been found to be highly conserved during evolution, to be widely distributed both in the central and peripheral nervous system and which act as neurotransmitters and/or neuromodulators. In the eye, the first peptide to be explored was substance P which was reported to be present in the retina but also in peripherally innervated tissues of the eye. Substance P is certainly the best characterized peptide which has been found in sensory neurons innervating the eye. Functionally, it has been shown to act trophically on corneal wound healing and to participate in the irritative response in lower mammals, a model for neurogenic inflammation, where it mediates the noncholinergic nonadrenergic contraction of the sphincter muscle. Over the last three decades, the interest has extended to investigate the presence and distribution of other neuropeptides including calcitonin gene-related peptide, vasoactive intestinal polypeptide, neuropeptide Y, pituitary adenylate cyclase-activating polypeptides, cholecystokinin, somatostatin, neuronal nitric oxide, galanin, neurokinin A or secretoneurin and important functional results have been obtained for these peptides. This review focuses on summarizing the current knowledge about neuropeptides in the eye excluding the retina and retinal pigment epithelium and to elucidate their potential functional significance.

Neurochemical properties of the middle cervical ganglion in the sheep

The neurochemical properties of the ovine middle cervical ganglion (MCG) were studied using antibodies raised against tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DbetaH), neuropeptide Y (NPY), substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP) and galanin (GAL). Double-labelling immunocytochemistry revealed that the vast majority (95.5 +/- 0.8%) of postganglionic sympathetic MCG neurons expressed simultaneously both catecholamine-synthesizing enzymes (neurons were TH/DbetaH-positive). A large population of noradrenergic neurons exhibited immunoreactivity (IR) to NPY (62.2 +/- 2.2%), but single NPY-positive perikarya-lacking noradrenergic markers were also observed (2.0 +/- 0.3%). None of the examined MCG neuronal somata contained SP, CGRP, GAL or VIP. A moderate number of noradrenergic nerve fibres located amongst neuronal cell bodies was also found. In small number of these terminals the presence of NPYor GAL (but not CGRP or VIP) was detected. The ovine MCG was numerously innervated with SP-immunoreactive nerve fibres which sometimes formed basket-like formations around postganglionic neurons. The MCG exhibited a sparse CGRP-immunoreactive innervation and lacked VIP-positive nerve terminals. In many aspects the chemical coding of MCG postganglionic neurons and nerve terminals resembles that found in other mammalian cervico-thoracic paravertebral ganglia, but some important species-dependent differences exist. The functional implications of these differences remain to be elucidated.

Ganglion-specific patterns of diabetes-modulated gene expression are established in prevertebral and paravertebral sympathetic ganglia prior to the development of neuroaxonal dystrophy

In both humans and animal models, diabetic sympathetic autonomic neuropathy is associated with the selective development of markedly enlarged distal axons and nerve terminals (neuroaxonal dystrophy, NAD). NAD occurs in the prevertebral superior mesenteric and celiac ganglia (SMG-CG), but not in the paravertebral superior cervical ganglion (SCG). To identify molecular differences between these ganglia that may explain their selective vulnerability to NAD, we have examined global gene expression patterns in control and diabetic rat sympathetic ganglia before and after the onset of structural evidence of NAD. As predicted, major differences in transcriptional profiles exist between SCG and SMG-CG in normal young adult animals including, but not limited to, known differences in neurotransmitter-related gene expression. Gene expression patterns of diabetic SMG-CG and SCG, prior to the development of NAD lesions, also differ from their age-matched non-diabetic counterparts. However, diabetes has ganglion-specific effects on gene expression; of approximately 110 transcripts that were differentially expressed between diabetic and control sympathetic ganglia, only 5 were differentially expressed as a result of diabetes in both SCG and SMG-CG. Genes involving synapse and mitochondrial structure and function, oxidative stress, and glycolysis were highly represented in the differentially expressed gene set. Differences in the number of synapse-related gene alterations in diabetic SMG-CG (18 genes) versus SCG (2 genes) prior to the onset of NAD may also well explain the selective development of NAD in the SMG-CG. These results provide support for the specificity of diabetes-modulated gene expression for selected neuronal subpopulations of sympathetic noradrenergic neurons.

Sigma receptors inhibit high-voltage-activated calcium channels in rat sympathetic and parasympathetic neurons

Studies on the expression and cellular function of sigma receptors in autonomic neurons were conducted in neonatal rat intracardiac and superior cervical (SCG) ganglia. Individual neurons from SCG and intracardiac ganglia were shown to express transcripts encoding the sigma-1 receptor using single-cell RT-PCR techniques. The relationship between sigma receptors and calcium channels was studied in isolated neurons of these ganglia under voltage-clamp mode using the perforated-patch configuration of the whole cell patch-clamp recording technique. Bath application of sigma receptor agonists was shown to rapidly depress peak calcium channel currents in a reversible manner in both SCG and intracardiac ganglion neurons. The inhibition of barium (I(Ba)) currents was dose-dependent, and half-maximal inhibitory concentration (IC50) values for haloperidol, ibogaine, (+)-pentazocine, and 1,3-Di-O-tolylguanidin (DTG) were 6, 31, 61, and 133 microM, respectively. The rank order potency of haloperidol > ibogaine > (+)-pentazocine > DTG is consistent with the effects on calcium channels being mediated by a sigma-2 receptor. Preincubation of neurons with the irreversible sigma receptor antagonist, metaphit, blocked DTG-mediated inhibition of Ca2+ channel currents. Maximum inhibition of calcium channel currents was > or =95%, suggesting that sigma receptors block all calcium channel subtypes found on the cell body of these neurons, which includes N-, L-, P/Q-, and R-type calcium channels. In addition to depressing peak Ca2+ channel current, sigma receptors altered the biophysical properties of these channels. Following sigma receptor activation, Ca2+ channel inactivation rate was accelerated, and the voltage dependence of both steady-state inactivation and activation shifted toward more negative potentials. Experiments on the signal transduction cascade coupling sigma receptors and Ca2+ channels demonstrated that neither cell dialysis nor intracellular application of 100 microM guanosine 5'-O-(2-thiodiphosphate) trilithium salt (GDP-beta-S) abolished the modulation of I(Ba) by sigma receptor agonists. These data suggest that neither a diffusible cytosolic second messenger nor a G protein is involved in this pathway. Activation of sigma receptors on sympathetic and parasympathetic neurons is likely to modulate cell-to-cell signaling in autonomic ganglia and thus the regulation of cardiac function by the peripheral nervous system.

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.