Presence and co-localization of vasoactive intestinal polypeptide with neuronal nitric oxide synthase in cells and nerve fibers within guinea pig intrinsic cardiac ganglia and cardiac tissue

The presence of vasoactive intestinal polypeptide (VIP) has been analyzed in fibers and neurons within the guinea pig intrinsic cardiac ganglia and in fibers innervating cardiac tissues. In whole-mount preparations, VIP-immunoreactive (IR) fibers were present in about 70% of the cardiac ganglia. VIP was co-localized with neuronal nitric oxide synthase (nNOS) in fibers innervating the intrinsic ganglia but was not present in fibers immunoreactive for pituitary adenylate cyclase-activating polypeptide, choline acetyltransferase (ChAT), tyrosine hydroxylase, or substance P. A small number of the intrinsic ChAT-IR cardiac ganglia neurons (approximately 3%) exhibited VIP immunoreactivity. These few VIP-IR cardiac neurons also exhibited nNOS immunoreactivity. After explant culture for 72 h, the intraganglionic VIP-IR fibers degenerated, indicating that they were axons of neurons located outside the heart. In cardiac tissue sections, VIP-IR fibers were present primarily in the atria and in perivascular connective tissue, with the overall abundance being low. VIP-IR fibers were notably sparse in the sinus node and conducting system and generally absent in the ventricular myocardium. Virtually all VIP-IR fibers in tissue sections exhibited immunoreactivity to nNOS. A few VIP-IR fibers, primarily those located within the atrial myocardium, were immunoreactive for both nNOS and ChAT indicating they were derived from intrinsic cardiac neurons. We suggest that, in the guinea pig, the majority of intraganglionic and cardiac tissue VIP-IR fibers originate outside of the heart. These extrinsic VIP-IR fibers are also immunoreactive for nNOS and therefore most likely are a component of the afferent fibers derived from the vagal sensory ganglia. This work was supported by NIH grant HL65481 (R.L.P.) and HL54633 (D.B.H.). Use of the DeltaVision Restoration microscope was provided through the Imaging/Physiology Core supported by NIH Grant P20 RR16435 from the COBRE program of the National Center for Research Resources     

Development of neuropeptide Y and tyrosine hydroxylase immunoreactive innervation in postnatal rat heart

Neuropeptide Y (NPY), immunoreactive (IR), and tyrosine hydroxylase (TH)-IR nerve fibers were scarce at birth in rat heart, but increased rapidly during the first 2 postnatal weeks, reaching approximately adult levels by the third week. The sequence of development was: interatrial septum and atrial wall, free ventricular wall starting from the epicardium, and finally the atrial appendages and interventricular septum. In ventricles and atrial appendages both fiber types developed similarly. In interatrial septum and atrial walls more NPY-IR than TH-IR fibers were evident, and NPY-IR, but not TH-IR, neurons were detected in intrinsic ganglia. Doublelabel immunohistochemistry provided further evidence that NPY is located in ventricular and atrial noradrenergic nerves, but is also located in nonnoradrenergic nerves in atria.     

Distribution of intrinsic cardiac neurons in whole-mount guinea pig atria identified by multiple neurochemical coding

Functional data indicate that neurons in distinct regions of the heart exert preferential regional cardiac control. To date the regional distribution of specific types of neurons within the intrinsic cardiac nervous system remains unknown, as does their associations with distinct neurotransmitter and/or neuromodulatory profiles. This study was designed to ascertain: (1) the distribution of different classes of neurons within the intrinsic cardiac nervous system as determined by microscopic analysis; (2) the neurochemical profiles of neurons in differing atrial loci; (3) which neurochemicals are co-localized within specific populations of intrinsic cardiac neurons; and (4) the distribution of specific sub-populations of neurons expressing specific immunoreactivities. Taking advantage of confocal laser scanning microscopy and distinct immunoreactive fluorescent markers in various double-label combinations, several sub-populations of intrinsic cardiac neurons were identified. Of all identified neurons, 85-90% were located in ganglia (ganglionic neurons), the rest being isolated (individual neurons). The two general neuronal markers protein gene product 9.5 (PGP 9.5) and microtubule-associated protein (MAP-2) were associated with neurons clustered primarily in the interatrial septum and around the origins of the two vena cavae. Ganglia (group 1) contained three sub-populations of neurons: approx. 80% of ganglionic neurons were large (15-40 microm diameters; group 1a) and approx. 20% had smaller diameters (less than 15 microm; group 1b). All of these neurons were PGP-immunoreactive, exhibiting choline acetyltransferase (ChAT) immunoreactivity (IR), tyrosine hydroxylase (TH) IR, neuropeptide Y (NPY) IR, vasoactive peptide (VIP) IR and substance P (SP) IR. The remaining 5% of ganglionic neurons were small (group 1c; less than 20 microm). These displayed TH immunoreactivity but not MAP, PGP, CHAT, NPY or SP immunoreactivity. Ten to fifteen percent of all neurons loosely distributed outside of ganglia were small (10-25 microm) and located primarily around the origin of the superior vena cava. They displayed immunoreactivity to TH, ChAT, VIP, NPY and SP, but not to MAP-2 or PGP 9.5. These data provide anatomical and immunohistochemical evidence for specific localization of differing populations of intrinsic cardiac neurons with respect to their size, ganglionic distributions and capacity to express multiple neurotransmitters. Although the functional importance of such a regional distribution of differing populations of intrinsic cardiac neurons remains unknown, these anatomical data support the thesis that unique clustering of specific populations of neurons within this nervous system represents the anatomical substrate for complex local cardiac regulatory phenomena occurring at the level of the target organ.     

Choline acetyltransferase immunoreactivity of putative intrinsic primary afferent neurons in the rat ileum

The colocalisation of choline acetyltransferase (ChAT) with markers of putative intrinsic primary afferent neurons was determined in whole-mount preparations of the myenteric and submucosal plexuses of the rat ileum. In the myenteric plexus, prepared for the simultaneous localisation of ChAT and nitric oxide synthase (NOS), all nerve cells were immunoreactive (IR) for ChAT or NOS, but seldom for both; only 1.6 +/- 1.8% of ChAT-IR neurons displayed NOS-IR and, conversely, 2.8 +/- 3.3% of NOS-IR neurons were ChAT-IR. In preparations double labelled for NOS-IR and the general nerve cell marker, neuron-specific enolase, 24% of all nerve cells were immunoreactive for NOS, indicating that about 75% of all nerve cells have ChAT-IR. All putative intrinsic primary afferent neurons in the myenteric plexus, identified by immunoreactivity for the neurokinin 1 (NK1) receptor and the neurokinin 3 (NK3) receptor, were ChAT-IR. Conversely, of the ChAT-IR nerve cells, about 45% were putative intrinsic primary afferent neurons (this represents 34% of all nerve cells). The cell bodies of putative intrinsic primary afferent neurons had Dogiel type II morphology and were also immunoreactive for calbindin. All, or nearly all, nerve cells in the submucosal plexus were immunoreactive for ChAT. About 46% of all submucosal nerve cells were immunoreactive for both neuropeptide Y (NPY) and calbindin; 91.8 +/- 10.5% of NPY/calbindin cells were also ChAT-IR and 99.1 +/- 0.7% were NK3 receptor-IR. Of the nerve cells with immunoreactivity for ChAT, 44.3 +/- 3.8% were NPY-IR, indicating that about 55% of submucosal nerve cells had ChAT but not NPY-IR. Only small proportions of the ChAT-IR, non-NPY, nerve cells had NK3 receptor or calbindin-IR. It is concluded that about 45% of submucosal nerve cells are ChAT/calbindin/NPY/VIP/NK3 receptor-IR and are likely to be secretomotor neurons. Most of the remaining submucosal nerve cells are immunoreactive for ChAT, but their functions were not deduced. They may include the cell bodies of intrinsic primary afferent neurons.     

Neurocalcin-like immunoreactivity in the rat esophageal nervous system

Neurocalcin is a newly identified neuronal calcium-binding protein. We tried here to investigate the immunohistochemical distribution of neurocalcin in the rat esophagus. Nerve cell bodies having neurocalcin immunoreactivity were found throughout the myenteric plexus. In the myenteric ganglia, two types of nerve terminals showed neurocalcin immunoreactivity. One was varicose terminals containing numerous small clear vesicles and forming a synapse with nerve cells. The other terminals were characterized by laminar or pleomorphic structure and many mitochondria. These laminar terminals were supposed to be sensory receptors of the esophageal wall. In the motor endplates of the striated muscles, nerve terminals containing many small clear vesicles and mitochondria also had neurocalcin immunoreactivity. After left vagus nerve cutting under the nodose ganglia, the number of immunopositive thick nerve fibers, laminar endings and nerve terminals on the striated muscles decreased markedly. Retrograde tracing experiments using Fast Blue showed extrinsic innervation of esophagus from ambiguus nucleus, dorsal motor nucleus of vagus, superior cervical ganglia, celiac ganglia, nodose ganglia and dorsal root ganglia. In the celiac ganglia, nodose ganglia and dorsal root ganglia, retrogradely labeled nerve cells were neurocalcin-immunoreactive. Neurons in the celiac ganglia may project varicose terminals, while nodose and dorsal root neurons project laminar terminals. Although cell bodies of motoneurons in the ambiguus nucleus lacked neurocalcin immunoreactivity, these neurons may contain neurocalcin only in the nerve terminals in the motor endplates. Neurocalcin immunoreactivity is distributed in many extrinsic and intrinsic neurons in the esophagus and this protein may play important roles in regulating calcium signaling in the neurons.     

Distribution of spinal sensory neurons supplying the adrenal gland in the pig

The present study was aimed at disclosing which spinal ganglia contribute to the innervation of the adrenal gland in the pig with special regard to the morphology and intraganglionic distribution of the primary sensory neurons within these ganglia. To this end, the animals were injected with a retrograde fluorescent neuronal tracer Fast Blue into the left adrenal gland during laparotomy. After a survival period of three weeks, labelled spinal sensory neurons were found in the ipsilateral dorsal root ganglia (approximately 99% of all retrogradely marked neurons). However, single adrenal gland-projecting perikarya were observed also in the contralateral dorsal root ganglia from Th3 to L3. The majority of the retrogradely labelled afferent neurons (above 65% of all Fast Blue-positive (FB+) perikarya) were located in two groups of spinal ganglia (at neuromeres Th6-7 and Th12-14, approximately 18% and 47% of neurons, respectively), forming two distinct multiganglionic centres of origin for this neural pathway. The morphometric evaluation of FB+ neurons revealed that the vast majority of them (approximately 81%) belonged to the class of small-sized perikarya (10-30 microm in diameter), while the medium-sized (diameter 30-80 microm) and large neurons comprised only up to 13% and 6.5% of adrenal gland-projecting neurons, respectively. Furthermore, the analysis of the intraganglionic distribution pattern of the retrogradely labelled cells revealed that the highest number of them was located in the medio-caudal domain of the dorsal root ganglia, irrespective of the neuromere studied. Thus, the present study has revealed sources and morphological characteristic of spinal afferent neurons supplying the porcine adrenal gland, simultaneously pointing out to the characteristic features of their inter- and intraganglionic distribution pattern.     

Some parasympathetic neurons in the guinea-pig heart express aspects of the catecholaminergic phenotype in vivo

Summary In a histochemical study of intrinsic cardiac ganglia of the guinea-pig in whole-mount preparations, it was found that some 70–80% of the neurons express aspects of the catecholaminergic phenotype. These neurons have an uptake mechanism for L-DOPA, and contain the enzymes for converting L-DOPA, (but not D-DOPA) to dopamine and noradrenaline, i.e. aromatic L-aminoacid decarboxylase and dopamine -hydroxylase. Monoamine oxidase is also present within some of the neurons. In these respects, the neurons resemble noradrenergic neurons of sympathetic ganglia, so we refer to them as intrinsic cardiac amine-handling neurons. However, these neurons do not contain tyrosine hydroxylase and show little or no histochemically detectable uptake of -methyldopa, dopamine or noradrenaline, even after depletion of endogenous stores of amines by pre-treatment with reserpine. Noradrenergic fibres from the sympathetic chain form pericellular baskets around nerve cell bodies. The uptake of L-DOPA into nerve cell bodies is not prevented by treatment with 6-hydroxydopamine sufficient to cause transmitter-depletion or degeneration of the extrinsic noradrenergic fibres. Such degeneration experiments suggest that axons of the amine-handling neurons project to cardiac muscle, blood vessels and other intrinsic neurons. The cardiac neurons do not show any immunohistochemically detectable serotonergic characteristics; there is no evidence for uptake of the precursors L-tryptophan and 5-hydroxytryptophan or 5-HT itself, whereas the extrinsic noradrer ergic nerve fibres within the ganglia can take up 5-HT when it is applied in high concentrations.Abbreviations AChE acetylcholinesterase - DBH-IR dopamine -hydroxylase-like immunoreactivity - L-DOPA L-dihydroxyphenylalamine - 5-HT-IR 5-hydroxytryptamine-like immunoreactivity - 6-OHDA 6-hydroxydopamine - methyldopa L--methyl-dihydroxyphenylalanine - MAO monoamine oxidase - NPY neuropeptide Y - SIF small intensely fluorescent cells - TH-IR tyrosine hydroxylase-like immunoreactivity - VIP vasoactive intestinal polypeptide     

Characteristics of GABAergic neurons and their synaptic relationships with intrinsic axons in the cat motor cortex

The intrinsic circuitry of the motor cortex comprises a complex network of connections whose synaptic relationships are poorly understood. This study was designed to determine the characteristics of subsets of GABAergic neurons containing the calcium-binding proteins parvalbumin (PV) and calbindin (CB), and their relationships with intrinsic axons in motor cortex. Immunohistochemically identified PV-containing neuronal profiles were more evenly distributed across cortical laminae (38% in II-III, 32% inV, 30% in VI) and more numerous (2.1/1) than CB-containing neuronal profiles (71% in II-III, 17% in V, 12% in VI). Relationships between neurons and axons intrinsic to motor cortex were visualized with fluorescent markers using the laser scanning confocal microscope. Similar percentages of PV (43%) and CB-immunoreactive (IR) (40%) neurons formed sparsely distributed appositions (1-5/neuron) with anterogradely labeled axons. The mean distances of such appositions from the somata were significantly different for the two groups (PV, mean = 22 microm, range = 1.6-93 microm; CB, mean = 32 microm, range = 6.2-132 microm). PV-IR neurons had a lower ratio of axosomatic/axodendritic appositions (1/99) compared with CB-IR neurons (14/86). Ultrastructural studies confirmed these findings. Fifty-seven percent of CB-IR neurons and 38% of PV-IR neurons formed synapses with intrinsic axons. Both populations received sparse input (1-6 synapses/neuron). Nearly all appositions between labeled terminals and postsynaptic profiles formed one synapse. Postsynaptic dendrites of PV-IR neurons (mean = 1.4 microm diameter) were larger than those of CB-IR neurons (mean = 1.1 microm), indicating more proximal synapses. Distinct input patterns of intrinsic axons to the two populations of neurons suggest unique roles in cortical processing.     

Calbindin immunoreactivity of enteric neurons in the guinea-pig ileum

Previous studies have identified Dogiel type II neurons with cell bodies in the myenteric plexus of guinea-pig ileum to be intrinsic primary afferent neurons. These neurons also have distinctive electrophysiological characteristics (they are AH neurons) and 82-84% are immunoreactive for calbindin. They are the only calbindin-immunoreactive neurons in the plexus. Neurons with analogous shape and electrophysiology are found in submucosal ganglia, but, with antibodies used in previous studies, they lack calbindin immunoreactivity. An antiserum that is more effective in revealing calbindin in the guinea-pig enteric nervous system has been reported recently. In the present work, we found that this antiserum reveals the same population that was previously identified in myenteric ganglia, and does not reveal any further population of myenteric nerve cells. In submucosal ganglia, 9-10% of nerve cells were calbindin immunoreactive with this antiserum. The submucosal neurons with calbindin immunoreactivity were also immunoreactive for choline acetyltransferase, but not for neuropeptide Y (NPY) or vasoactive intestinal peptide (VIP). Small calbindin-immunoreactive neurons (average profile 130 microm2) were calretinin immunoreactive, whereas the large calbindin-immunoreactive neurons (average profile 330 microm2) had tachykinin (substance P) immunoreactivity. Calbindin immunoreactivity was seen in about 50% of the calretinin neurons and 40% of the tachykinin-immunoreactive submucosal neurons. It is concluded that, in the guinea-pig ileum, only one class of myenteric neuron, the AH/Dogiel type II neuron, is calbindin immunoreactive, but, in the submucosal ganglia, calbindin immunoreactivity occurs in cholinergic, calretinin-immunoreactive, secretomotor/vasodilator neurons and AH/Dogiel type II neurons.     

Chronic decentralization of the heart differentially remodels canine intrinsic cardiac neuron muscarinic receptors

The objective of the study was to determine if chronic interruption of all extrinsic nerve inputs to the heart alters cholinergic-mediated responses within the intrinsic cardiac nervous system (ICN). Extracardiac nerve inputs to the ICN were surgically interrupted (ICN decentralized). Three weeks later, the intrinsic cardiac right atrial ganglionated plexus (RAGP) was removed and intrinsic cardiac neuronal responses were evaluated electrophysiologically. Cholinergic receptor abundance was evaluated using autoradiography. In sham controls and chronic decentralized ICN ganglia, neuronal postsynaptic responses were mediated by acetylcholine, acting at nicotinic and muscarinic receptors. Muscarine- but not nicotine-mediated synaptic responses that were enhanced after chronic ICN decentralization. After chronic decentralization, muscarine facilitation of orthodromic neuronal activation increased. Receptor autoradiography demonstrated that nicotinic and muscarinic receptor density associated with the RAGP was unaffected by decentralization and that muscarinic receptors were tenfold more abundant than nicotinic receptors in the right atrial ganglia in each group. After chronic decentralization of the ICN, intrinsic cardiac neurons remain viable and responsive to cholinergic synaptic inputs. Enhanced muscarinic responsiveness of intrinsic cardiac neurons occurs without changes in receptor abundance.     

Immunohistochemical analysis of intracardiac ganglia of the rat heart

The neurochemistry of intracardiac neurons in whole-mount preparations of the intrinsic ganglia was investigated. This technique allowed the study of the morphology of the ganglionated nerve plexus found within the atria as well as of individual neurons. Intracardiac ganglia formed a ring-like plexus around the entry of the pulmonary veins and were interconnected by a series of fine nerve fibres. All intracardiac neurons contained immunoreactivity to PGP-9.5, choline acetyl transferase (ChAT) and neuropeptide Y (NPY). Two smaller subpopulations were immunoreactive to calbindin or nitric oxide synthase. Furthermore, a subpopulation (approximately 6%) of PGP-9.5/ChAT/NPY-immunoreactive cells lacking both calbindin and nitric oxide synthase (NOS) was surrounded by pericellular baskets immunoreactive to ChAT and calbindin. Vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase-activated peptide (PACAP), substance P and tyrosine hydroxylase (TH) immunoreactivity was observed in nerve fibres within the ganglion, but never in neuronal somata. Furthermore, immunoreactivity for NPY was not observed in pericellular baskets surrounding intracardiac neurons, despite being present in all intrinsic neuronal cell bodies. Taken together, the results of this study indicate a moderate level of chemical diversity within the intracardiac neurons of the rat. Such chemical diversity may reflect functional specialisation of neurons in the intracardiac ganglia.This work was supported by a grant-in-aid (G00M0670) from the National Heart Foundation of Australia     

Sources of porcine longissimus dorsi muscle (LDM) innervation as revealed by retrograde neuronal tract-tracing

The aim of the present study was to establish the origin of the motor, autonomic and sensory innervation of the L1-L2 segment of the porcine longissimus dorsi muscle (LDM), in order to provide morphological basis for further studies focusing on this neural pathway under experimental conditions, e.g. phototerapy and/or lateral electrical surface stimulation. To reach the goal of the study, multiple injections of the fluorescent neuronal tracer Fast Blue (FB) were made into the LDM region between the spinal processes of the vertebrae L1 and L2. The spinal cord (Th13-S1 segments) as well as the sensory and autonomic ganglia of interest, i.e., dorsal root (DRG) and sympathetic chain ganglia from corresponding spinal cord levels were collected three weeks later. FB-positive (FB+) motoneurons were observed exclusively within the nucleus ventromedialis at L1 and L2 spinal cord level, forming the most ventro-medially arranged cell column within this nucleus. Primary sensory and sympathetic chain neurons were found in appropriate ipsilateral ganglia at Th15-L3 levels. The vast majority of retrogradely traced neurons (virtually all motoneurons, approximately 76% of sensory and 99.4% of sympathetic chain ganglia neurons) was found at the L1 and L2 levels. The morphometric evaluation of FB-labeled DRG neurons showed that the majority of them (approximately 66%) belonged to the class of small-diameter perikarya (10-30 microm in diameter), whereas those of medium size (30-80 microm in diameter) and of large diameter (more than 80 microm) constituted 22.6% and 11.5% of all DRG neurons, respectively. The results of the present study demonstrated that the nerve terminals supplying porcine LDM originated from different levels of the spinal cord, dorsal root and sympathetic chain ganglia. Thus, the study has revealed sources and morphological characteristic of somatic, autonomic and spinal afferent neurons supplying porcine LDM, simultaneously pointing out the characteristic features of their distribution pattern.     

Distribution of Peptide-Containing Neurons in the Developing Rat Right Atrium,Studied Using Immunofluorescence and Confocal Laser Scanning

The developmental pattern and distribution of peptide-containing neurons in the rat heart right atrium has been studied by indirect immunofluorescence. Antibodies against neuropeptide Y (NPY), substance P (SP), and vasoactive intestinal polypeptide (VIP) were applied to whole-mount stretch preparations of the right atria from hearts of newborn to 40-day-old animals. NPY-like immunoreactivity (LI) was compared with the synaptic vesicle marker SV2 in double immunoincubation studies. The distribution of immunofluorescence was studied by confocal laser scanning microscopy. NPY-LI and SP-LI were present throughout the atria already at birth, in contrast to VIP-LI that was observed at day 10. The postnatal changes of innervation were basically quantitative, with an increase in density of nerve fibres and number of varicosities, while the basic pattern of innervation was essentially established during the first 1–10 days. NPY- and SP-positive bundles of fibres appeared to enter the right atrium along the superior caval vein, having extrinsic origins. Nerve fibres with NPY-LI colocalized in most nerve terminals with SV2-LI, and showed a developmental pattern similar to that observed for adrenergic neurons earlier. These NPY/SV2 positive fibres probably represent the extrinsic NPY innervation. In addition, NPY-LI was identified in large intrinsic nerve cells bodies located near the atrioventricular (AV) region. Most of the VIP-LI was observed in short nerve fibres originating in intrinsic VIP-positive cell bodies, but a few apparently extrinsic VIP-positive fibres were found, probably representing preganglionic parasympathetic neurons. SP in the atria was probably of extrinsic (sensory) origin and no nerve cell bodies with SP-LI were detected. The results show that the peptidergic innervation in the developing rat right atrium involves both extrinsic and intrinsic peptidergic neurons which may participate in the regulation of neurotransmission in local neuronal circuits.     

Cholinergic activation of the lobster cardiac ganglion

The frequency of rhythmic burst activity of the isolated lobster cardiac ganglion is increased by exogenously applied acetylcholine and muscarinic agonists. Responses of individual motor neurons isolated from the ganglion by transection consist of a slow depolarization and repetitive bursting. The pharmacological profile of the receptors mediating this response is similar to that of vertebrate neuronal muscarinic receptors. Isolated ganglia incubated in the presence of [3H]-choline (18-19 h) exhibited radiolabelled acetylcholine accumulation. It is suggested that ganglionic excitation may be accomplished by extrinsic or intrinsic activation of muscarinic receptors on the motor neurons.     

Butyrate enemas enhance both cholinergic and nitrergic phenotype of myenteric neurons and neuromuscular transmission in newborn rat colon

Postnatal changes in the enteric nervous system (ENS) are involved in the establishment of colonic motility. In adult rats, butyrate induced neuroplastic changes in the ENS, leading to enhanced colonic motility. Whether butyrate can induce similar changes during the postnatal period remains unknown. Enemas (Na-butyrate) were performed daily in rat pups between postnatal day (PND) 7 and PND 17. Effects of butyrate were evaluated on morphological and histological parameters in the distal colon at PND 21. The neurochemical phenotype of colonic submucosal and myenteric neurons was analyzed using antibodies against Hu, choline acetyltransferase (ChAT), and neuronal nitric oxide synthase (nNOS). Colonic motility and neuromuscular transmission was assessed in vivo and ex vivo. Butyrate (2.5 mM) enemas had no impact on pup growth and histological parameters compared with control. Butyrate did not modify the number of Hu-immunoreactive (IR) neurons per ganglia. A significant increase in the proportion (per Hu-IR neurons) of nNOS-IR myenteric and submucosal neurons and ChAT-IR myenteric neurons was observed in the distal colon after butyrate enemas compared with control. In addition, butyrate induced a significant increase in both nitrergic and cholinergic components of the neuromuscular transmission compared with control. Finally, butyrate increased distal colonic transit time compared with control. We concluded that butyrate enemas induced neuroplastic changes in myenteric and submucosal neurons, leading to changes in gastrointestinal functions. Our results support exploration of butyrate as potential therapy for motility disorders in preterm infants with delayed maturation of the ENS.     

Galanin is more common than NPY in vascular sympathetic neurons of the brush-tailed possum.

The distribution of galanin (Gal) in sympathetic vascular neurons of adult and juvenile brush-tailed possums (Trichosurus vulpecula), was examined using double-labelling immunohistochemistry. This was compared with the distribution of neuropeptide Y (NPY) in the same tissues. Immunoreactivity (IR) to galanin was present in the majority (64-99%) of nerve cell bodies in paravertebral sympathetic ganglia, where it mostly co-existed with IR to the catecholamine-synthesizing enzyme, tyrosine hydroxylase (TH). Gal-IR also was present in most, if not all, TH-IR perivascular axons supplying systemic arteries and veins. NPY-IR was less common than Gal-IR in all sympathetic ganglia and perivascular axons examined. Some sympathetic, TH-IR axons supplying the abdominal aorta and renal artery contained both Gal-IR and NPY-IR, while TH-IR axons supplying cephalic and thoracic vessels contained Gal-IR but not NPY-IR. Limited observations on sympathetic neurons in two species of wallabies indicated that Gal-IR also was more common than NPY-IR in other marsupial species, but the incidence of NPY-IR was higher in these wallabies than in the brush-tailed possum. Together with previous studies, this work suggests that the coexistence of galanin and NPY may be the primitive condition for sympathetic neurons in tetrapods. The differential expression of these peptides in specific populations of sympathetic neurons may have important functional consequences in the autonomic control of the circulation.     

Vasoactive intestinal peptide (VIP)-like immunoreactivity in the human sympathetic ganglia

Vasoactive intestinal peptide immunoreactive (VIP-IR) nerve fibres and terminals, neurons and small granule containing cells were observed in human lumbal sympathetic ganglia. Electron-microscopically VIP-IR was localized in the large dense-cored vesicles in nerve terminals and on the membranes of the Golgi complexes in the neurons. A small population of principal ganglion cells was surrounded by VIP-IR nerve terminals. Most of these neurons contained acetylcholinesterase (AChE) enzyme but were not tyrosine hydroxylase-immunoreactive (TH-IR). All VIP-IR ganglion cells and most of the nerve fibres contained AChE but not TH-IR. It appears that in human sympathetic ganglia VIP is localized in the cholinergic neurons and nerve fibres and that the VIP-IR nerve terminals innervate mainly the cholinergic subpopulation of the sympathetic neurons.