Immunohistochemical evidence for extrinsic and intrinsic opioid systems in the guinea pig superior cervical ganglion

Coexistence of enkephalin- and tyrosine hydroxylase-like immunoreactivities in nerve fibers of the temporomandibular joint capsule of the guinea pig

BACKGROUND

The innervation of joints has been suggested to play an important role for their normal function as well as for the pathogenesis of chronic arthritic conditions. It is therefore important to elucidate the functional anatomy of this innervation.

METHODS

The expression of methionine enkephalin-like immunoreactivity (ENK-LI) and tyrosine hydroxylase (TH)-LI as well as their possible colocalization were examined in the temporomandibular joint of the guinea pig:

RESULTS

Nerve fibers with ENK-LI were demonstrated in the synovium of the guinea pig temporomandibular joint capsule with the use of indirect immunofluorescence. The ENK+ fibers were found close to the surface of the synovial membrane, deeper in the synovium, and at the walls of blood vessels. Coexistence of ENK- and TH-LI was observed frequently in the synovial nerve fibers. After removal of the superior cervical ganglion (SCG), the ENK-containing nerve fibers were reduced substantially in number on the operated side or were completely absent if the cervical sympathetic trunk was also excised.

CONCLUSIONS

The findings indicate that the majority of fibers with ENK-LI derive from the SCG ENK may act as a neuromodulator on the catecholaminergic nerves and may also have an analgesic effect in the joint.

Opioidergic innervation of the tree shrew pineal gland: an immunohistochemical study

The tree shrew (Tupaia glis) has been described as a missing link relating primate to insectivore stock. The pineal gland of the tree shrew consists of a superficial pineal and a deep pineal, which are connected by a long and slender pineal stalk. A monoclonal antibody against leu-enkephalin was used in an immunohistochemical investigation of the tree shrew pineal gland. A moderate innervation of leu-enkephalin immunoreactive nerve fibers has been demonstrated in both superficial and deep pineal gland of the tree shrew. The density of the nerve fibers was slightly higher in the superficial pineal than that of the deep one. The number of immunoreactive nerve fibers were observed in the capsule of the pineal gland from where they entered the pineal parenchyma. Only a few immunoreactive fibers were found in the habenular area and the area rostral to the pineal recess, connecting the habenula and the deep pineal. Furthermore, some positive fibers were located in the pineal stalk. There was no evidence of leu-enkephalin immunoreactive intrapineal cells as seen in the other species of mammal. Therefore, the interspecies variation of opioidergic innervation among the mammals may exist. The lack of intrapineal perikarya is interpreted to indicate that the sources of leu-enkephalin nerve fibers were outside the gland. The anatomical location of the leu-enkephalin immunoreactive nerve fibers in the tree shrew pineal gland supports to both central and peripheral pinealopetal pathways in this species.

Nociceptin and its receptor in guinea-pig sympathetic ganglia

The occurrence and distribution of nociceptin, a 17-amino acid peptide with structural similarity to dynorphin A, and its receptor, opioid receptor-like-1 (ORL1) receptor, were investigated in the guinea-pig sympathetic nervous system by means of immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR), respectively. Immunofluorescence revealed varicose nociceptin-immunoreactive axons and some paraganglionic cells in prevertebral (coeliaco-superior mesenteric, inferior mesenteric), but not in paravertebral (superior cervical, stellate, lumbar chain) sympathetic ganglia. Messenger RNA for the ORL1 receptor, however, was detected by RT-PCR in both para- and prevertebral ganglia. The findings suggest participation of the nociceptin/ORL1 receptor signalling pathway in processing of information within prevertebral ganglia, and a general responsiveness of sympathetic neurons to nociceptin.

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.

Immunohistochemical correlation of human adrenal nerve fibres and thoracic dorsal root neurons with special reference to substance P

Applying a double-labelling immunofluorescence technique, six types of substance P-containing nerve fibres were distinguished in the human adrenal gland according to the immunohistochemical colocalization of (I) calcitonin gene-related peptide (CGRP), (II) cholecystokinin, (III) nitric oxide synthase, (IV) dynorphin, (V) somatostatin, and (VI) vasoactive intestinal polypeptide. Fibre populations I to IV in their mediator content resembled the respective subpopulations of primary sensory neurons in human thoracic dorsal root ganglia, while populations V and VI revealed no correspondence with dorsal root neurochemical coding. Nerve fibres with the combination substance P/nitric oxide synthase occurred only in the adrenal cortex, whereas all other fibre types were present in both cortex and medulla. As revealed by immuno-electron microscopy, substance P-immunolabelled axon varicosities (a) exhibited synaptic contacts with medullary chromaffin cells or with neuronal dendrites, (b) were directly apposed to cortical steroid cells and (c) were separated from fenestrated capillaries only by the interstitial space. These findings provide immunochemical support for an assumed sensory innervation of the human adrenal gland, and additionally suggest participation of substance P in efferent autonomic pathways. Furthermore, the results are indicative for a differentiated involvement of substance P in the direct and indirect regulation of neuroneuronal and neuroendocrine interactions.

Preganglionic sympathetic neurones, innervating the guinea pig adrenal medulla, immunohistochemically contain choline acetyltransferase and also leu-enkephalin

Applying retrograde neuronal tracing combined with double labelling immunofluorescence, 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-acetyltransferase (ChAT) and sometimes, also for leu-enkephalin. Likewise, ChAT-immunoreactive nerve fibres, forming a dense meshwork in the adrenal medulla, partly contained immunostaining also for leu-enkephalin. Some of the intramedullary nerve cell bodies were ChAT-positive but were non-reactive for leu-enkephalin. The findings provide evidence for an extrinsic (preganglionic) and an intrinsic (postganglionic) cholinergic nerve system in the guinea pig adrenal medulla, the preganglionic system utilising leu-enkephalin as co-mediator.

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

The localization of [Met5]enkephalin-Arg6-Gly7-Leu8 and [Met5]enkephalin immunoreactivities was studied in the rat superior cervical ganglion. The distribution of these enkephalin-containing peptides in the ganglion was correlated to that of neuropeptide Y and vasoactive intestinal polypeptide. Three different populations of peptide-containing postganglionic neurons were demonstrated. (1) A minor population (10-20%) of principal neurons was immunoreactive for [Met5]enkephalin-Arg6-Gly7-Leu8 but not immunoreactive for neuropeptide Y nor vasoactive intestinal polypeptide. (2) The major population (about 50-70%) was immunoreactive for neuropeptide Y but not for [Met5]enkephalin-Arg6-Gly7-Leu8. (3) Few vasoactive intestinal polypeptide-immunoreactive principal neurons (less than 2% of all principal neurons) were observed in the ganglion. All vasoactive intestinal polypeptide-immunoreactive neurons were also immunoreactive for neuropeptide Y but not for [Met5]enkephalin-Arg6-Gly7-Leu8. [Met5]enkephalin-Arg6-Gly7-Leu8- and [Met5]enkephalin-immunoreactive nerve fibers had a similar distribution. These enkephalin immunoreactive nerve fibers were seen to enclose both neuropeptide Y-containing principal neurons and neurons devoid of neuropeptide Y immunoreactivity. Furthermore, there were enkephalin-immunoreactive fiber baskets around vasoactive intestinal polypeptide-immunoreactive neurons and sometimes also around solitary enkephalin-immunoreactive neurons. Previously reported diverse role of enkephalins in the rat superior cervical ganglion is supported by this study.

Immunohistochemical localization of neuropeptides in the porcine thoraco-lumbar paravertebral ganglia

The existence and distribution pattern of neuropeptide Y, Met5-enkephalin-Arg6-Gly7-Leu8, vasoactive intestinal polypeptide, calcitonin gene-related peptide, substance P and bombesin/gastrin releasing peptide in the neuronal elements of the thoracolumbar paravertebral ganglia (T4-L6) were studied immunohistochemically in sexually immature female pigs. Subpopulations of nerve cell bodies containing immunoreactivity to neuropeptide Y, Met5-enkephalin-Arg6-Gly7-Leu8, vasoactive intestinal polypeptide and calcitonin gene-related peptide were described. However, neurons were non-immunoreactive for substance P and bombesin/gastrin releasing peptide. The solitary small intensely fluorescent cells contain calcitonin gene-related peptide-, substance P- and Met5-enkephalin-Arg6-Gly7-Leu8-, whereas the some cells in clusters contained only substance P and only substance P and Met5-enkephalin-Arg6-Gly7-Leu8. Immunoreactivities to all studied peptides occurred in the nerve fibres within investigated ganglia. Additionally the number of nerve fibres containing particular peptides as well as their distribution pattern were found to vary. The results of this study were compared with those of previous investigations in other species.

Ultrastructural connectivity of [leu]5-enkephalin-immunoreactive synapses in the guinea-pig stellate ganglion: involvement of spines and triads

The ultrastructure of [leu]5-enkephalin-immunoreactive (ENK-IR) nerve fibres in the guinea-pig stellate ganglion was studied by means of pre-embedding immunohistochemistry. ENK-immunoreactivity was primarily contained within large dense core vesicles (91 +/- 21 nm in diameter; n = 259) but was absent from small clear vesicles (47 +/- 9 nm; n = 488) within the same nerve terminal that were concentrated at presynaptic regions. Thus, fast synaptic transmission mediated by ENK-IR terminals most probably does not involve [leu]5-enkephalin which may be released parasynaptically. Evaluating a total number of 123 synapses involving an ENK-IR presynaptic nerve ending, 47% terminated upon a spine, 46% upon a dendritic shaft, and 7% directly addressed a soma of a postganglionic neuron. In 30% of axo-dendritic synapses and 33% of axo-somatic synapses, non-immunoreactive dendrites or somata being postsynaptic to an ENK-IR terminal were in direct but non-synaptic contact to another dendrite/soma. Such arrangements are termed "triads". In view of the current hypotheses concerning the function of spines and triads, these findings indicate that ENK-IR terminals within the guinea-pig stellate ganglion may be involved in the generation of long-lasting synaptic events and modulation of non-synaptic intraganglionic communication.

Neuronal specificity and plasticity in the autonomic nervous system

The autonomic nervous system is divided into the sympathetic, parasympathetic and enteric subdivisions. The present review is focussed upon the highly specialized reflex organization and neurochemistry of sympathetic parasympathetic neurons. The currently available informations allow to conclude that autonomic control of each peripheral target tissue is specifically regulated under normal conditions but nevertheless able to respond to altered conditions by changes in neural activity and mediator expression.

The sensory and sympathetic innervation of guinea-pig lung and trachea as studied by retrograde neuronal tracing and double-labelling immunohistochemistry

The sympathetic and sensory innervation of guinea-pig trachea and lung were studied by means of retrograde neuronal tracing using fluorescent dyes, and double-labelling immunofluorescence. Sympathetic neurons supplying the lung were located in stellate ganglia and in thoracic sympathetic chain ganglia T2-T4; those supplying the trachea resided in the superior cervical and stellate ganglia. Retrogradely labelled sympathetic neurons were usually immunoreactive to tyrosine hydroxylase; the majority also contained neuropeptide Y immunoreactivity. However, a small number were non-catecholaminergic (i.e. tyrosine hydroxylase negative), but neuropeptide Y immunoreactive. Within the airways, tyrosine hydroxylase/neuropeptide Y-immunoreactive axons were found in the smooth muscle layer, around blood vessels including the pulmonary artery and vein, and to a lesser extent in the lamina propria. Periarterial axons contained in addition dynorphin immunoreactivity. Sensory neurons supplying the lung were located in jugular and nodose vagal ganglia as well as in upper thoracic dorsal root ganglia; those supplying the trachea were most frequently found bilaterally in the nodose ganglia and less frequently in the jugular ganglia. A spinal origin of tracheal sensory fibres could not be consistently demonstrated. With regard to their immunoreactivity to peptides, three types of sensory neurons projecting to the airways could be distinguished: (i) substance P/dynorphin immunoreactive; (ii) substance P immunoreactive but dynorphin negative; and (iii) negative to all peptides tested. Substance P-immunoreactive neurons innervating the airways invariably contained immunoreactivity to neurokinin A and calcitonin gene-related peptide. Retrogradely labelled neurons located in the nodose ganglia belonged almost exclusively (greater than or equal to 99%) to the peptide-negative group, whereas the three neuron types each represented about one-third of retrogradely labelled neurons in jugular and dorsal root ganglia. Within the airways, axons immunoreactive to substance P/neurokinin A and substance P/calcitonin gene-related peptide were distributed within the respiratory epithelium of trachea and large bronchi, in the lamina propria and smooth muscle from the trachea down to the smallest bronchioli (highest density at the bronchial level), in the alveolar walls, around systemic and pulmonary blood vessels, and within airway ganglia. Those axons also containing dynorphin immunoreactivity were restricted to the lamina propria and smooth muscle. The origin of nerve fibres immunoreactive for vasoactive intestinal polypeptide, of which a part were also neuropeptide Y immunoreactive, could not be determined by retrograde tracing experiments. Vasoactive intestinal polypeptide-immunoreactive fibres terminating within airway ganglia may be of preganglionic parasympathetic origin, whereas others (e.g. those found in smooth muscle) may arise from intrinsic ganglia.(ABSTRACT TRUNCATED AT 400 WORDS)

Naloxone-sensitive inhibition of nicotinic transmission in the superior cervical ganglion of the cat

In anesthetized, artificially ventilated cats, pretreated with the muscarinic antagonist scopolamine, the effect of naloxone on the efficacy of nicotinic transmission in the superior cervical ganglion was used as a test of endogenous opioid release by the preganglionic axons. The cervical sympathetic trunk (CST) was split into two bundles. The compound action potential (CAP), evoked by supramaximal low-frequency stimulation (0.25 Hz) of one CST bundle, was recorded from a postganglionic nerve of the superior cervical ganglion. Partial block with hexamethonium was used to reduce the 'safety factor' of nicotinic transmission. A conditioning train (5 Hz, 40 s, supramaximal) to the other CST bundle (heterosynaptic conditioning) inhibited the CAP. At the peak of the inhibition the CAP was attenuated by 51 +/- 4%. Recovery was 90% complete in 201 +/- 28 s. The inhibition was antagonized in a dose-dependent manner by i.v. naloxone with an apparent IC50 of 60 +/- 12 micrograms/kg. The maximum effect obtained with naloxone was an 80% decrease in the magnitude of the inhibition. Magnitude and duration of the heterosynaptic inhibition were related to frequency, duration and intensity of the conditioning train. Naloxone-sensitive inhibition was observed with frequencies of the conditioning train as low as 0.5 Hz. A train (5 Hz, 40 s) to the postganglionic nerves produced a naloxone-insensitive depression of the orthodromic test CAP which was of smaller amplitude and duration than when the conditioning train was applied to the preganglionic axons.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of Met-enkephalyl-Arg-Gly-Leu in rat larynx: partial coexistence with vasoactive intestinal polypeptide, peptide histidine isoleucine and neuropeptide Y

Using light microscopic (LM) enzyme-immunohistochemistry on deparaffinized adjacent sections Met-enkephalyl-Arg-Gly-Leu (ME-RGL) immunoreactivity was found to partially coexist with immunoreactive neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI) in intrinsic laryngeal neurons of the rat. Further ME-RGL-immunoreactive (ir) fibres were found around glands in the subepithelium, in connective tissue of striated muscle and in the perichondrium, as well as around arterial and venous blood vessels. They frequently contacted mast cells and macrophages. The presence of ME-RGL indicates pro-enkephalin-related origin of this novel laryngeal opioid system. From the specific target relations and close interrelations of fibres staining for opioids with those staining for the other peptides--which are known to be more or less characteristic of the sympathetic (NPY), parasympathetic (VIP, PHI) and sensory (calcitonin gene-related peptide; CGRP) subdivisions of the peripheral nervous system--we deduce that opioid/non-opioid interactions might co-control various laryngeal functions, e.g. glandular secretion, blood flow, immune and inflammatory responses and/or might be of relevance in trophic mechanisms.

Three types of neurochemically defined autonomic fibres innervate the carotid baroreceptor and chemoreceptor regions in the guinea-pig

The innervation of the carotid body, carotid sinus, and neighbouring arteries (common carotid artery; external carotid artery; occipital artery; ascending pharyngeal artery) was investigated in guinea-pigs by means of glyoxylic acid-induced catecholamine-fluorescence and immunohistochemistry using a variety of antisera against neuropeptides and tyrosine hydroxylase (TH). Fibres displaying catecholamine-fluorescence, TH- and neuropeptide Y-like immunoreactivity (NPY-LI) were less numerous in the carotid sinus than in all other arterial segments. Vasoactive intestinal polypeptide (VIP)-LI axons were almost lacking in the common carotid, external carotid and occipital arteries, consistently found in the carotid sinus, and more numerous in the ascending pharyngeal artery. Catecholaminergic, TH-, NPY- and VIP-LI fibres were observed deep in the media of the carotid sinus, where the baroreceptor terminals are located. In contrast, they did not enter the media in the adjacent arterial segments. All these fibres disappeared following excision of the superior cervical ganglion, but were unaffected by combined transection of the carotid sinus nerve and resection of the no-dose ganglion, suggesting a sympathetic origin. Double-staining immunofluorescence revealed at least three types of autonomic, presumably sympathetic fibres in the carotid sinus: 1) TH+/NPY+, 2) NPY+/VIP+, and 3) VIP+ fibres. This points to a non-noradrenergic efferent innervation of the carotid sinus in addition to the hitherto known noradrenergic sympathetic fibres. The three populations of autonomic fibres seen in the carotid sinus were also observed in the carotid body, but the paucity of NPY+/VIP+ double-labelled fibres raises doubt as to the functional significance of this particular fibre type in modulating arterial chemoreception. The multiplicity of neurochemically defined autonomic nerves to the carotid baro- and chemoreceptor regions probably reflects functionally separate pathways that are differently regulated and exert different effects.

Neuronal pathways in the guinea-pig lumbar sympathetic ganglia as revealed by immunohistochemistry

Tyrosine hydroxylase (TH)- and peptide-immunoreactivity of postganglionic neurons and of nerve fibres in guinea pig lumbar paravertebral sympathetic ganglia 2-4 after transection of the communicating rami and the visceral branches, respectively, were investigated by single- and double-labelling techniques. Six subpopulations of postganglionic neurons were discriminated immunohistochemically: two cell types, which were immunoreactive to only one of the applied antisera - TH, and vasoactive intestinal polypeptide (VIP); and four cell types in which immunoreactivity was colocalized - TH/neuropeptide Y (NPY), NPY/VIP, dynorphin/alpha-neoendorphin and dynorphin (alpha-neoendorphin)/NPY. Small intensely fluorescent (SIF) cells dependent on their location exhibited differential immunobehaviour to NPY-/dynorphin-(alpha-neoendorphin-) and TH-antisera. Immunoreactivity to substance P (SP), calcitonin gene-related peptide (CGRP), met-enkephalin-arg-phe (MEAP) and leu-enkephalin was present in nerve fibres but not in postganglionic neurons with frequent colocalization of SP/CGRP- and MEAP/leu-enkephalin- and, sometimes leu-enkephalin/SP- and dynorphin/SP-immunoreactivity. TH-immunoreactive intraganglionic nerve fibres were numerically more increased after cutting the visceral branches, than after transection of the communicating rami. Vice versa, NPY-, VIP-, dynorphin- and alpha-neoendorphin-immunoreactive nerve fibres were particularly increased in number after cutting the communicating rami. Many but not all of the nerve fibres exhibited colocalization of two of these peptides. SP-, CGRP-, and enkephalin-immunoreactive nerve fibres were not visibly affected by cutting the visceral branches but virtually disappeared after lesioning the communicating rami.

Sympathetic noradrenergic neurons containing dynorphin but not neuropeptide Y innervate small cutaneous blood vessels of guinea-pigs

We have used double-labelling immunofluorescence techniques and retrograde axonal transport of Fast Blue to characterize three populations of sympathetic noradrenergic neurons innervating blood vessels in the hairless skin of the ears and paws of guinea-pigs. Each population of neurons innervated a specific level of the vascular bed, and had a distinctive content of neuropeptides. Sympathetic noradrenergic neurons innervating large distributing arteries contained immunoreactivity to neuropeptide Y. Neurons innervating smaller cutaneous arteries contained immunoreactivity to prodynorphin-derived peptides in addition to neuropeptide Y. Finally, sympathetic neurons innervating the smallest arterioles, and arterio-venous anastomoses, contained immunoreactivity to prodynorphin-derived peptides, but had no detectable neuropeptide Y. Although the major form of dynorphin immunoreactivity in perivascular sympathetic axons was dynorphin A(1-8), immunoreactivity to both dynorphin A(1-8) and dynorphin A(1-17) occurred in the cell bodies of these neurons, suggesting that dynorphin A is processed during axonal transport to the terminals. The perivascular sympathetic neurons containing prodynorphin-derived peptides but not neuropeptide Y are most likely to be involved in the regulation of thermoregulatory cutaneous vascular circuits.

Immunocytochemical analysis of [Met5]enkephalin-Arg6-Gly7-Leu8 immunoreactive structures in the rat superior cervical ganglion

Indirect immunofluorescence and immunoelectron microscopy were employed to analyze the enkephalinergic systems in the rat superior cervical ganglion (SCG). These systems were identified using specific antiserum against [Met5]Enkephalin-Arg6-Gly7-Leu8 (ENK-8), a peptide which is derived only from proenkephalin A. Abundant ENK-8 like immunoreactive (ENK-8-LI) neurons and fibers were observed in the SCG, but their distribution patterns were heterogenous; ENK-8-LI neurons were localized preferentially in the caudal two-thirds of the SCG, while immunoreactive fibers were found to be distributed more densely in the rostral one-third than in the remaining part of the SCG. Most of the ENK-8-LI neurons were large and had ultrastructural features resembling those of principal cells, some were identified electron microscopically as small intensely fluorescent (SIF) cells. ENK-8-LI fibers were varicose in appearance and surrounded the perikarya of neurons. Since most of these fibers were not detected after experimental decentralization of the SCG and since ENK-8-LI terminals were seen to contain small lucent vesicles, most of the former were thought to be preganglionic fibers. Immunoreactive fibers mainly formed synaptic contacts with the dendrites of non-immunoreactive principal cells, but a small proportion of ENK-8-LI principal cells also received synaptic input from them. Occasionally, immunoreactive fibers formed synapses with the processes or the soma of both ENK-8-LI and non-immunoreactive SIF cells. On the basis of these findings, we conclude that: (1) preganglionic ENK-8-LI fibers terminate mainly on the principal cells, which are devoid of ENK-8-LI structures; (2) the majority of ENK-8-LI neurons are principal cells, while the remainder are SIF cells; (3) inputs to these cells mainly involve structures lacking ENK-8 immunoreactivity; and (4) there are, however, a small number of ENK-8-LI preganglionic fibers which terminate on ENK-8-LI principal cells and SIF cells.

Co-localization and plasticity of transmitters in peripheral autonomic and sensory neurons

Immunohistochemical studies have shown that most peripheral autonomic and sensory ganglia are heterogeneous, consisting of several populations of neurons which can be distinguished by their content of peptide and non-peptide transmitters, and transmitter-associated enzymes. Many neurons contain several different potential transmitters, especially neuropeptides. Some neuropeptides have been localized in more than one population of autonomic and sensory neurons. However, the peptide often occurs together with a distinctive combination of additional transmitters in each neuronal class. The precise combination of transmitters found in any individual neuron is highly correlated with the peripheral target of the neuron. This indicates that immunohistochemically defined neuronal populations represent distinct functional classes of neurons. In an increasing number of cases, many of the potential transmitters contained in a particular neuron have been shown to be released from the nerve terminals, and to contribute to presynaptic or postsynaptic effects of nerve activation. Despite this association between the combination of potential transmitters contained in a neuron, and the function of the neuron, not all transmitters or transmitter-associated enzymes are expressed equally at all times in the life of a neuron: the levels of some substances change dramatically during development; some are detected only after experimental alteration of the environment of the developing or mature neurons. Taken together, these results indicate that, during development, pathway-specific information influences the differentiation of peripheral autonomic and sensory neurons. Furthermore, the expression of neuropeptides and transmitter-associated enzymes in a particular neuron appears to be under continuous regulation. These phenomena demonstrate the complexity and precision involved in development and maintenance of the peripheral autonomic and sensory nervous systems.

Immunohistochemical evidence for the presence of peptides derived from proenkephalin, prodynorphin and proopiomelanocortin in the guinea pig pineal gland

By using a plethora of region-specific antisera, this light microscopic immunohistochemical study revealed that derivatives from the three opioid precursors, i.e. proenkephalin, prodynorphin and proopiomelanocortin are differentially distributed in the pineal gland of guinea pig. Various molecular forms of immunoreactive opioid peptides derived from proenkephalin or prodynorphin were present in a minority of pinealocytes as well as in nerves. In contrast to this dual distribution pattern of opioid-active peptides, the opioid-inactive derivative from proopiomelanocortin, alpha-melanocyte stimulating hormone, was exclusively present in a large proportion of pinealocytes. A multiple and differential origin and function of opioidergic pineal innervation involving sympathetic, parasympathetic and sensory components is suggested. alpha-MSH is proposed as a pineal hormone which may act in concert with melatonin to regulate pineal rhythms or may function like MSH of pituitary origin.

Immunohistochemistry of biogenic polypeptides in nerve cells and fibres of the guinea pig inferior mesenteric ganglion after perturbations

Immunohistochemistry of peptide- and dopamine-beta-hydroxylase-(DBH)-containing varicose nerve fibres and ganglion cells, respectively, in the guinea pig inferior mesenteric ganglion was investigated following a) transsection of mesenteric (colonic) branches, b) transsection of central (lumbar splanchnic, intermesenteric and hypogastric) branches, and c) transplantation into the spleen. The findings indicate that pathways of different opioid peptides are not identical. Met-enkephalin- and met-enkephalin-arg-phe- (cleavage products from pre-proenkephalin) containing fibres course in central branches to make contact in the inferior mesenteric ganglion. Dynorphin- and alpha-neo-endorphin- (deriving from pre-prodynorphin) containing fibres as well as leu-enkephalin- (included in the dynorphin sequence) fibres appear to rise not only from central and from enteric somata, but also from intraganglionic noradrenergic neurons. Similar pathways seem to be used by VIP- and by neurotensin-immunoreactive fibres, although intraganglionic neurotensin-immunoreactive cell bodies are rare. Practically all substance P- and most CGRP-immunoreactive fibres enter the ganglion via central branches and, to a large extent, traverse it, but some CGRP-immunoreactive influx appears to come from the intestine. The origin of intraganglionic substance P- and CGRP-immunoreactive fibres after ganglion transplantation remained unidentified. Somatostatin- and neuropeptide Y-immunoreactive fibres predominantly have an intraganglionic origin as have DBH-immunoreactive noradrenergic fibres. The demonstrated alterations in neuropeptide immunoreactivity of intraganglionic and periganglionic nerve fibres following the applied transsection procedures contribute to the present knowledge on origin and destination of peptidergic transmitter segments in the guinea pig inferior mesenteric ganglion. Moreover, the present study provides evidence that intrinsic participation in intraganglionic fibre supply is more extensive than hitherto believed.