Occurrence of vasoactive intestinal polypeptide (VIP)-like immunoreactivity in certain cholinergic neurons of the cat: evidence from combined immunohistochemistry and acetylcholinesterase staining

Activation of choline acetyltransferase by vasoactive intestinal peptide

Addition of vasoactive intestinal peptide (VIP) to brain homogenates increased the activity of choline acetyltransferase (ChAT) but not that of acetylcholinesterase or glucose-6-phosphate dehydrogenase. Activity of ChAT was increased in the anterior hypothalamus and in the dorsal and ventral hippocampus, but not in the parietal cortex or posterior hypothalamus. Increased activity occurred rapidly after VIP addition to homogenates and was maximal at 10(-7)M concentration. Kinetic analysis indicates that the Vmax of the enzyme is increased and the Km for choline, but not acetyl-coenzyme A, is decreased in the presence of VIP. Results support a possible VIP-cholinergic interaction in the CNS.

VIP and noradrenaline act synergistically to increase cyclic AMP in cerebral cortex

There is growing evidence that two, or possibly more, neurotransmitters can coexist within the same neurone. In particular, the presence of a peptide and a biogenic amine has been demonstrated in the same terminals of central and peripheral neurones. These findings have led to the hypothesis that neurotransmitters, coexisting within the same neurones, can interact at pre- or postsynaptic sites in a functionally coordinated manner. However, interactions between neurotransmitters contained in distinct neuronal systems terminating within the same region of the central nervous system (CNS) can be envisaged. We have examined this last possibility in the cerebral cortex, an area of the CNS where the two neurotransmitters vasoactive intestinal polypeptide and noradrenaline are contained in separate neuronal systems and where they both stimulate the formation of cyclic AMP. We report here that vasoactive intestinal polypeptide and noradrenaline act synergistically to stimulate the formation of cyclic AMP and that this synergistic interaction is antagonized by the specific alpha-adrenergic antagonist phentolamine.

Chronic atropine treatment causes increase in VIP receptors in rat cerebral cortex

Chronic atropine treatment (14 days, 20 mg X day-1 X kg-1 SC) caused a 75% increase in the number of VIP receptors in the rat cerebral cortex. The affinity of these receptors for 125I-VIP was not altered significantly by the atropine treatment. The same treatment led to a 20% decrease in VIP tissue levels. Muscarinic receptor number was also increased by 26%. The results indicate that interactions between VIP- and muscarinic receptors may be of importance in the rat cerebral cortex.

Distribution of neurones containing DOPA decarboxylase and dopamine-beta-hydroxylase in some sympathetic ganglia of the dog: a quantitative study

Using a technique by which binding sites for two antibodies can be visualized in single tissue sections, we have studied the distribution of neurones containing DOPA decarboxylase-like and dopamine beta-hydroxylase-like immunoreactivity in ganglia of dog sympathetic chain. Three types of neurones could be distinguished: those that contained both enzymes, and were presumably noradrenergic; those that contained neither enzyme, and were presumably not catecholaminergic; and a group that contained DOPA decarboxylase but lacked dopamine beta-hydroxylase. The numbers of cells of each type were counted in serially-sectioned ganglia from regions of the sympathetic chain thought to contain dopaminergic neurones (T12-L1 and L7-S2). The percentages of total cell numbers contributed by the DOPA decarboxylase-positive, dopamine beta-hydroxylase-negative cells in these regions were similar to the estimates of dopaminergic neurone numbers that can be made from previously obtained biochemical data. Our results are consistent with the presence of dopaminergic neurons in regions of the paravertebral chain supplying the kidney and the distal hindlimb.

Development of VIP in the peripheral nervous system of avian embryo

The distribution of the VIP containing structures was studied in the gut and in the paravertebral sympathetic ganglia of the quail and chick embryos by immunocytochemistry. In the gut, development of peptidergic nerves followed a craniocaudal gradient. Immunoreactive fibres were first visible in the oesophagus at day 9 in the quail and day 10 in the chick, at 12 days they extended over the whole length of the gut. Cell bodies were localized at day 9 in the foregut and observed in the mid- and hind-gut just before hatching. Transplantations on the chorioallantoic membrane of fragments of various parts of the digestive tract clearly demonstrated that VIP nerve cell bodies belonged to the intrinsic innervation of the gut. Besides the gut, sympathetic paravertebral ganglia contained cells with VIP immunoreactivity detected at day 9 and 10 in quail and chick respectively. In order to find out whether VIP containing neurons differentiated normally in chick embryos in which quail neural crest cells had been implanted at an early stage of development we looked for the appearance of peptidergic neurones in the following situations: when the quail neural primordium had been grafted orthotopically and isochronically into chick host (1) at the adrenomedullary (somites 18-24) and (2) at the vagal (somites 1-7) levels of the neural axis. In all conditions VIP immunoreactivity was observed in quail cells located either in the sympathetic paravertebral ganglia of the trunk at the level of the graft or in the enteric ganglia according to the graft was made at the adrenomedullary and vagal levels respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence that vasoactive intestinal polypeptide is a dilator transmitter to some cerebral and extracerebral cranial arteries

Many arteries of the head upon electrical stimulation of the non-adrenergic nerve terminals present in their wall exhibit dilation that is only partially reduced by atropine. The results of three types of experiments are presented that tend to implicate vasoactive intestinal polypeptide (VIP) a known vasodilator, as an atropine-resistant dilator transmitter. VIP activity is high in vessels that exhibit neurogenic dilation and low in those that do not. It is released from two arteries that show such dilation upon neurogenic field stimulation and VIP antiserum reduces neurogenic dilation. It is proposed that VIP as well as acetylcholine are released from the innervation of some cranial arteries and together in a number of animals of least are responsible for part of the complex neurogenic dilation witnessed in these vessels. Although substance P is present in nerves found within the wall of cerebral and other cranial blood vessels, it is either ineffective as a dilator in vessels that show a sizeable dilation to electrical stimulation, or else exhibits marked, rapid, persistent tachyphylaxis.

Occurrence of neurotensinlike immunoreactivity in subpopulations of hypothalamic, mesencephalic, and medullary catecholamine neurons

By using indirect immunofluorescence histochemistry combined with the elution-restaining technique, the presence of a neurotensinlike peptide in some catecholamine neurons in the rat brain has been demonstrated. At the level of the medulla oblongata neurotensinlike immunoreactivity was observed in most of the small-sized catecholamine (adrenaline) cell bodies in the dorsolateral part of the nucleus of the solitary tract and in some catecholamine (noradrenaline) cells in the medial part. Neurotensin-positive fibers were found throughout the solitary tract nucleus with increasing concentrations in the rostral direction. Very few neurotensin fibers were seen in the vagal dorsal motor nucleus, which contained a dense network of adrenaline fibers. In the ventral mesencephalon, neurotensinlike immunoreactivity was seen mainly in dopamine cell bodies in the ventral tegmental area, including midline structures, with only single examples of coexistence in the substantia nigra. The dopamine cell bodies of both the A9 and A10 cell groups were surrounded by dense to medium-dense networks of neurotensin fibers. In the hypothalamus numerous dopamine neurons in the arcuate nucleus exhibited neurotensinlike immunoreactivity. Neurotensin-positive nerve terminals, partially overlapping catecholamine (mainly dopamine) fibers, were seen in the external layer of the median eminence. The present results demonstrate coexistence of neurotensinlike immunoreactivity and catecholamines in populations of neurons in some of the central catecholamine cell groups and provide a morphological basis for interactions between the peptide and amines.

Neuropeptides contained in peripheral cardiovascular nerves

The neuropeptides, substance P, vasoactive intestinal peptide (VIP), neuropeptide Y and enkephalin have been found in nerves associated with the heart and blood vessels of a range of mammals, including man. There is also evidence for some cardiovascular nerves with gastrin releasing peptide and neurotensin immunoreactivity. Substance P is in sensory nerves with a widespread distribution to the heart and all vascular beds. In general, large arteries have the densest innervation and the density of nerves decreases as arterial size decreases. In adult guinea-pigs, an adequate treatment with capsaicin causes the degeneration of almost all cardiovascular substance P nerves. Using capsaicin as a tool it has been shown that the substance P containing sensory nerves are not essential for baroreceptor reflexes. VIP nerves also have a widespread distribution, being particularly prominent in the cerebral arteries, uterine arteries and arteries of erectile and secretory tissues. Neuropeptide Y is located in the same cardiovascular nerves as noradrenaline. It is depleted from the nerves by reserpine or 6-hydroxydopamine. Enkephalin nerves have been reported with small arteries in only a few vascular beds.

Localization of vasoactive intestinal polypeptide in penile erectile tissue and in the major pelvic ganglion of the rat

Vasoactive intestinal polypeptide was localized by immunocytochemical techniques in the major pelvic ganglion and penile erectile tissue of the rat. Vasoactive intestinal polypeptide fibers were concentrated in penile crura with the density of innervation decreasing distally. The helicine arteries were very densely innervated while fewer fibers surrounded the deep artery of the penis. Intrinsic smooth muscle of the cavernous bodies received a moderate supply of vasoactive intestinal polypeptide immunoreactive fibers. Dorsal vascular structures, including the deep dorsal vein were innervated by vasoactive intestinal polypeptide fibers. Vasoactive intestinal polypeptide immunoreactive cell bodies were found in the major pelvic ganglion, concentrated on one end of the ganglion. Retrograde studies with a dye injected into the penile crura indicated that neurons in major pelvic ganglion projected to the penis. Combined dye and immunofluorescent studies showed that all the dye-labeled neurons were immunoreactive for vasoactive intestinal polypeptide. It is concluded that all vascular beds in the penis of the rat are innervated by vasoactive intestinal polypeptide fibers and that the extent of the innervation is related to the occurrence of smooth muscle. Neurons in the major pelvic ganglion probably are the main source of vasoactive intestinal polypeptide fibers to the penis.

Sensory substance P-innervation of the urinary bladder: possible site of action of capsaicin in causing urine retention in rats

In rats treated neonatally with capsaicin there is, in later life, a tendency tendency towards urine retention. Since capsaicin is known to cause irreversible loss of certain primary sensory neurons, notably those containing substance P, we have studied the sensory innervation of the bladder in capsaicin-treated and control rats using retrograde tracing methods and immunohistochemistry; in addition, the motor function of the bladder was assessed in in vitro experiments, using electrical field stimulation. Five days after injection of the fluorescent tracer True Blue into the wall of the bladder, numerous labelled cells were identified in dorsal root ganglia T13, L1, L2, L6, and S1 and smaller numbers of cells were found in T12 and L3. In capsaicin-treated rats the numbers of labelled cells were reduced by over 50% in L1, L6 and S1. In control rats, 10-16% of True Blue labelled cells also contained substance P as demonstrated by indirect immunofluorescence, but in capsaicin-treated rats substance P cells were virtually absent. In in vitro studies, contractions of the detrusor muscle to electrical field stimulation, both before and after atropine, were similar in control and capsaicin-treated rats. We suggest that capsaicin causes urine retention in rats due to an impairment of sensory transmission from the bladder (that could involve substance P) and a consequent failure in the normal micturition reflexes.

Regulation of enzymes responsible for neurotransmitter synthesis and degradation in cultured rat sympathetic neurons. I. Effects of muscle-conditioned medium

The enzymatic machinery for neurotransmitter synthesis and breakdown have been compared in sister cultures of newborn rat sympathetic neurons grown for 12-28 days either in the presence (CM+ cultures) or in the absence (CM- cultures) of a culture medium conditioned by rat skeletal muscle cells. Neuron numbers, total protein, and lactate dehydrogenase activities were identical in CM+ and CM- cultures. Choline acetyltransferase activity was 27- to 100-fold higher in homogenates of CM+ than CM- cultures, whereas acetylcholinesterase activity was 2.5-fold lower. The activities of tyrosine hydroxylase (TOH), DOPA decarboxylase, and dopamine beta-hydroxylase were all about twofold lower in homogenates from CM+ cultures. All these effects were also observed in homogenates of sympathetic neuron cultures grown with and without a macromolecular factor partially purified from CM (Weber, J. (1981). Biol. Chem. 256, 3447-3453.). Experiments of mixing homogenates from CM+ and CM- cultures suggested that the differences in each of the enzyme activities did not result from differences in the concentrations of hypothetical reversible enzyme activators and/or inhibitors. In addition, the deficit in TOH activity in CM+ cultures resulted from a decrease in the enzymatic Vmax with no significant variation in the apparent Km's for the substrate and the cofactor. An identical decrease in the Vmax was observed if TOH was assayed under phosphorylating or nonphosphorylating conditions, suggesting that this decrease did not result from differences in the state of enzyme phosphorylation. Immunoprecipitation curves of TOH activity by an anti-TOH antiserum were parallel when performed on homogenates from CM+ and CM- cultures, suggesting a difference in the number of enzyme molecules without detectable alteration of their kinetic properties.

Innervation of the cerebral vasculature

With the development of specific antibodies to vasoactive peptides and application of immunohistochemistry and radioimmunoassay methods, knowledge of vascular innervation has grown rapidly. In the cerebral circulation, four possible neurotransmitters are present: norepinephrine, acetylcholine, vasoactive intestinal peptide (VIP), and substance P. There is a dense adrenergic innervation of cerebral arteries, but contractile responses to nerve stimulation or circulating catecholamines are relatively small both in vitro and in vivo. Recent studies using radioligand binding techniques indicate a lack of specific 3H-prazosin binding in cerebral arteries, in contrast to other vascular beds. Thus a lack of alpha1-adrenergic receptors in cerebral arteries may account for weak responsiveness to sympathetic stimulation. Both VIP and acetylcholine may be vasodilator neurotransmitters, but blockade of cholinergic responses does not alter neurogenic vasodilation. The lack of specific VIP antagonists hampers efforts to explore this system more fully. Substance P-containing nerves are affected by capsaicin, supporting the hypothesis that these are primary sensory afferents, perhaps mediating pain. Future work in this area may focus on defining the pathways of these nerves and exploring the role of co-transmitters and possible interactions between nerves. With this basic information, experiments can be designed to elucidate more clearly the functional roles these nerves play.

Vasoactive intestinal peptide inhibitory innervation in bovine mesenteric lymphatics. A histochemical and pharmacological study

The localization of vasoactive intestinal peptide-immunoreactive nerves innervating bovine lymphatic vessels was studied by an immunohistochemical technique. Nerve fibers containing vasoactive intestinal peptide immunoreactivity were present in the smooth muscle layers as well as in the adventitia of all mesenteric lymphatics that were examined. The effect of vasoactive intestinal peptide on isolated lymphatic vessels in vitro was studied. Vasoactive intestinal peptide caused a concentration-dependent relaxation of bradykinin-induced contractions of lymphatic vessels. The threshold and maximum relaxations were achieved with vasoactive intestinal peptide at concentrations less than 6 X 10(-9) M and 3 X 10(-7) M, respectively. The relaxant response to vasoactive intestinal peptide was not modified by atropine, propranolol, bretylium, or tetrodotoxin. These results suggest that vasoactive intestinal peptide may be a possible inhibitory neurotransmitter that causes relaxation of lymphatic vessels.

Morphological and functional aspects of pancreatic islet innervation

Pancreatic islets are collections of 4 functionally-related endocrine cells distributed nonrandomly in the pancreas. Their major physiological actions center about the regulation of metabolic homeostasis. Experimental evidence shows that, in addition to circulating substates, the islets are controlled by outflow from the central nervous system communicated through autonomic nerves. Islet cells also interact with one another via hormonal messengers and, possibly, electrotonic impulses producing a complex--yet well-controlled--system for the integration of numerous types of signals. This paper is a brief review of some of the numerous interactions between the autonomic nervous system and the endocrine pancreas. Particular emphasis is placed on the role of recently discovered autonomic factors and newly recognized autonomic centers in the brain.

Immunohistochemical localization of substance P, vasoactive intestinal polypeptide and gastrin-releasing peptide in vas deferens and seminal vesicle, and the effect of these and eight other neuropeptides on resting tension and neurally evoked contractile activity

Immunohistochemical studies of the vas deferens and seminal vesicle of mouse, guinea-pig, and rabbit showed the presence of nerve fibres containing vasoactive intestinal polypeptide (VIP), substance P (SP), and gastrin-releasing peptide (GRP) supplying the smooth muscle layers as well as blood vessels. The nerve supply was better developed in the seminal vesicle than in the vas deferens. The motor activity of the vas deferens and seminal vesicle of the guinea-pig was studied in vitro. The vas deferens responded to transmural electrical stimulation with a twitch followed by a slow contraction. The twitch was blocked by guanethidine and tetrodotoxin, but not by atropine, propranolol, phenoxybenzamine, or fluphenazine. The slow contraction exhibited features of an alpha-receptor-mediated response. SP, physalaemin and eledoisin contracted the smooth muscle and also potentiated the twitch response to electrical nerve stimulation in a concentration-dependent manner. The SP blocking agent, (D-Pro2,D-Trp7,9)-SP, affected neither the resting tension nor the response to electrical stimulation. It is therefore suggested that the SP fibres act mainly prejunctionally. VIP, Leu-enkephalin, cholecystokinin octapeptide (CCK-8), angiotensin II, vasopressin, neurotensin, bombesin, and GRP had no effect on either the resting tension or the response to electrical nerve stimulation. The seminal vesicle responded to electrical stimulation with a contraction which was unimpaired by atropine, propranolol, phenoxybenzamine, and guanethidine, but abolished by tetrodotoxin. Hence, this contraction is mediated by a non-adrenergic, non-cholinergic neurotransmitter. Bombesin, GRP, SP, physalaemin and eledoisin contracted the smooth muscle and potentiated the response to electrical stimulation. VIP, Leu-enkephalin, CCK-8, angiotensin II, vasopressin, and neurotensin had no effect on the resting tension or on the response to transmural electrical stimulation. The SP antagonist abolished the contraction elicited by SP but did not influence the response to nerve stimulation. The results suggest that the SP and GRP nerves may have prejunctional and facilitating postjunctional effects in the seminal vesicle.

Light and electron microscopic immunocytochemical localization of vasoactive intestinal polypeptide VIP-like activity in the rat small intestine

Vasoactive intestinal polypeptide nerve processes and cell bodies were identified by electron microscopic immunocytochemistry in the rat small intestine. Labeled nerve processes were numerous in the inner circular smooth muscle coat and mainly in the mucosa, but were absent in the longitudinal muscle layer. Submucosal blood vessels were often surrounded by immunoreactive vasoactive intestinal polypeptide positive nerves, in close associations (distance less than 40 mn) to blood vessel basement membranes and to smooth muscle cells. In the ganglia of the myenteric and submucous plexuses, labeled fibers surrounded unstained neural cell bodies. The synaptic vesicles of vasoactive intestinal polypeptide positive terminals were 35-40 nm in diameter and some dense core vesicles (80-120 nm in diameter) were also observed in the same profiles. These observations suggest that vasoactive intestinal polypeptide nerves may participate in regulating smooth muscle activity and local blood flow in the small intestine.

Evidence for neurotransmitter plasticity in vivo: developmental changes in properties of cholinergic sympathetic neurons

We have examined the cholinergic sympathetic innervation of sweat glands in footpads of adult and developing rats. Acetylcholinesterase staining reveals a plexus of heavily stained fibers in the sweat glands of adult rats. Reaction product appears among and around bundles of axons that lie at a considerable distance from the cells of the secretory tubule. Each bundle contains 8-12 axons that possess numerous varicosities and contain small clear and large dense core vesicles. The glands of the hindpaws and their innervation develop during the first three weeks after birth. Catecholamine-containing axons were associated with the forming glands. At 7 and 10 days, intensely fluorescent fibers surrounded the tubules, and all of the axon profiles associated with the glands contained small granular vesicles (SGV) after permanganate fixation to reveal vesicular stores of norepinephrine. At 14 days the sweat gland plexus was less intensely fluorescent than at earlier ages and relatively few SGV were present. By 21 days, no endogenous catecholamine fluorescence and no SGV were detectable. However, following exposure to exogenous catecholamine, fluorescent fibers were present in the sweat glands of mature rats and they corresponded in position and density to the plexus localized with acetylcholinesterase staining. Catecholamine uptake was blocked by incubation in the cold and by desmethylimipramine and was not observed in cholinergic parasympathetic fibers in the iris or salivary glands. After intraperitoneal administration of 5-hydroxydopamine and permanganate fixation, all the axons in the sweat glands contained a few SGV. Thus, the developing sweat glands appear to be innervated by noradrenergic axons that lose their stores of endogenous catecholamines but not their capacity for uptake and storage as they elaborate an axonal plexus in the maturing glands. These observations support the hypothesis that cholinergic sympathetic neurons appear to undergo a transition from noradrenergic to cholinergic function during development in vivo similar to that previously described in cell culture.

Coexistence of neuropeptides in hydra

Using a technique for simultaneous visualisation of two antigens in one section, oxytocin-like immunoreactivity has been found to coexist with bombesin-like immunoreactivity in neurons of the basal disk, gastric region and tentacles of hydra. Neurons with oxytocin-like immunoreactivity in peduncle and hypostome, on the other hand, have little or no bombesin-like material. Oxytocin-like immunoreactivity never coexists with FMRFamide-immunoreactivity. The neurons with oxytocin- and FMRFamide-like immunoreactivity, however, are often found to be closely intermingled. The results show that coexistence, as well as non-coexistence, of neuropeptides is a phylogenetically old principle.

Immunoreactive somatostatin and vasoactive intestinal polypeptide in adrenal pheochromocytoma. An immunochemical and ultrastructural study

An adrenal pheochromocytoma producing somatostatin (SRIF) and vasoactive intestinal polypeptide (VIP) in a 17-year-old boy is presented. High concentrations of immunoreactive (IR)-SRIF were found in plasma taken from the antecubital vein (31.0-33.0 pg/ml) and the inferior caval vein near the tumor (54.6 pg/ml), but after removal of the tumor the values became normal (11.0-15.2 pg/ml). In two portions of the resected tumor, considerable but different amounts of IR-SRIF (151.7 and 12.1 ng/g wet wt) and IR-VIP (13.0 and 5.5 ng/g wet wt) were demonstrated with size heterogeneities. Immunohistochemically, many IR-SRIF cells and a few IR-VIP cells were observed, but no cell reacting with both anti-SRIF and anti-VIP sera was found. Electronmicroscopically, many tumor cells had catecholamine-like granules (250-350 nm in diameter) while some others had VIP-like granules (110-140 nm in diameter). However, no granules resembling the SRIF granules seen in the pancreatic D cells were found. This seems to be the first report of an adrenal pheochromocytoma that produces SRIF and VIP simultaneously. It provides information on the histogenesis of hormone-producing neurogenic tumors.

Vasoactive intestinal peptide-like immunoreactivity in nerves associated with the cardiovascular system of guinea-pigs

The distribution of nerves with vasoactive intestinal peptide (VIP)-like immunoreactivity has been examined in the heart and vascular system of guinea-pigs. There was a very sparse supply of fibres to the heart. No immunoreactive cell bodies were found in the intrinsic cardiac ganglia; however, positive nerve cell bodies were seen along the superior vena cava near the right atrium. There were immunoreactive fibres with most arteries; these fibres were located at the media-adventitia junction. The supply to major distributing arteries, such as the aorta, subclavian, carotid and femoral arteries as well as to the pulmonary arteries, was sparse. Of the individual vascular beds, the most densely supplied arteries were the mesenteric and uterine (or in the male deferential) arteries. Arteries running to other organs or tissues, such as skeletal muscle, kidney, pancreas, spleen and heart were less densely supplied. There were clear differences in the innervation of different cerebral vessels. The greatest density was associated with the anterior and middle cerebral arteries. Fewer nerves accompanied the posterior cerebral, cerebellar and meningeal arteries. There was a sparse innervation of the rostral part of the basilar artery. Throughout the body, veins were sparsely supplied. The distribution of nerves with VIP-like immunoreactivity was not changed when noradrenergic nerves were degenerated by 6-hydroxydopamine or when substance P nerves were disrupted by capsaicin. It is concluded that VIP containing nerves innervating the heart and blood vessels form a population distinct from the substance P-containing and the noradrenergic nerves. It is suggested that the VIP fibres might be efferent vasodilator nerves to the blood vessels.

Vasoactive intestinal peptide stimulation of pineal serotonin-N-acetyltransferase activity: general characteristics

Vasoactive intestinal polypeptide (VIP) stimulates basal serotonin-N-acetyltransferase (NAT) activity in pineals in organ culture and enhances the effects of catecholamines in inducing the enzyme. VIP appears to act postsynaptically; its action is independent of the beta receptor and is dependent upon protein synthesis. Its effects may be mediated by a receptor. The magnitude of the pineal response to VIP varies with age, is greater in pineals maintained in 48-h organ culture than in those in acute culture, and can be detected in pineals from newborns after 48-h organ culture. Intravenous administration of VIP can increase pineal NAT activity in vivo.

Localization of enkephalin-like immunoreactivity in acetylcholinesterase-positive cells in the guinea-pig lateral superior olivary complex that project to the cochlea

Olivocochlear fibers have been demonstrated to have acetylcholinesterase-positive staining both in brainstem and cochlea. Olivocochlear fibres in the cochlea have also been determined to contain enkephalin-like immunoreactivity. In this study, we first determined the source of olivocochlear fibers in the guinea-pig using horseradish peroxidase and wheat germ agglutinin in retrograde transport studies. These cells were then examined for enkephalin-like immunoreactivity followed by acetylcholinesterase staining on the same sections to determine which cells and fibers showed staining for both. It was found that cells in the guinea-pig lateral superior olive that project to the cochlea have both enkephalin-like immunoreactivity staining and acetylcholinesterase-positive staining. Cells in other areas giving rise to olivocochlear fibers showed only acetylcholinesterase staining. These results suggest that there is co-localization of enkephalin and acetylcholine in a population of olivocochlear cells and fibers.

Distribution of bombesin, somatostatin, substance-P and vasoactive intestinal polypeptide in feline and porcine skin

The content and distribution of several regulatory peptides in the skin of cats and pigs, freshly obtained at surgery, have been investigated. Immunoreactive bombesin was evenly distributed at low concentrations in both species, being below the detection limit in the body and nose of the cat, and showing a peak value of 1.6 +/- 0.7 pmol/g in the tip of the pig's ear. Similar concentrations of somatostatin-immunoreactivity (-IR) were found but greater regional variation occurred in the pig with a low in the mid back of 0.4 +/- 0.1 and the highest value in the snout of 3.1 +/- 0.8. Substance-P-IR in the pig showed a marked variation in concentration, apparently parallelling skin sensitivity, with a low in the back of 0.4 +/- 0.7 and higher values around the anus (8.1 +/- 1.6), legs (6.8 +/- 1.8) and snout (13.5 +/- 3.6) whilst in the cat values ranged from 0.3 +/- 0.06 in the body to 5.0 +/- 0.9 in the front footpads. In contrast, vasoactive intestinal polypeptide (VIP)-IR showed greater variability in the cat, being below the assay's detection in the body and highest in the front and rear footpads (17 +/- 7 and 29 +/- 6 respectively), but in the pig most regions exhibited low concentrations with the exception of the snout which peaked at 12.0 +/- 5.0. Immunocytochemical localisation showed the peptides to be present in nerve fibres. Substance-P-IR was particularly localised in the snout of the pig just below the epithelium while VIP-IR was more concentrated in deeper layers, often associated with sweat glands and blood vessels.

Light and agonists alter pineal N-acetyltransferase induction by vasoactive intestinal polypeptide

Vasoactive intestinal polypeptide stimulated serotonin N-acetyltransferase activity in rat pineal glands in organ culture by a postsynaptic action that was independent of the beta-receptor. The magnitude of stimulation could be altered by environmental lighting conditions and by prior exposure to the agonist. Such up- and down-regulation, well known for catecholaminergic stimulation of this system, is compatible with a possible control of the pineal by vasoactive intestinal polypeptide as well as by catecholamines.

VIP innervation of the tongue in vertebrates

An immunohistochemical study was carried out in order to investigate the occurrence of vasoactive intestinal polypeptide (VIP) in intralingual nervous tissue of different species. The study revealed that VIP-immunoreactive (IR) nerves and ganglia were widely found in all species studied. The following areas of the tongue tissue contain VIP-IR nerves: (1) Within the perivascular plexus many VIP-IR nerves can be found adjoining AV-anastomoses and medium-sized arteries, whereas the veins exhibit only a moderate number. (2) Intralingual ganglia contain VIP-IR perikarya and varicosities. (3) Lingual glands are regularly innervated by VIP-IR periglandular plexus. (4) Sub- and intraepithelial nerves react to VIP immunohistochemically and occur in different locations. The results of this study indicate that VIP is an important neuropeptide of the intralingual nerves. It is suggested that VIP has various functions as a neurotransmitter and/or neuromodulator which may be summarized as follows: (1) the vascular and glandular innervation can be assumed to be of an efferent nature, and (2) some subepithelial and intraepithelial nerves are afferent fibers.

Origin of peptide-containing fibers in the inferior mesenteric ganglion of the guinea-pig: immunohistochemical studies with antisera to substance P, enkephalin, vasoactive intestinal polypeptide, cholecystokinin and bombesin

After different denervation procedures the guinea-pig inferior mesenteric ganglion was analysed by immunohistochemistry using antisera to substance P, enkephalin, vasoactive intestinal polypeptide, cholecystokinin and bombesin. The results demonstrate that each of the nerve trunks connected to the ganglion carries specific peptidergic pathways. Thus, the lumbar nerves contain substance P-immunoreactive primary afferent neurons, which to a large extent traverse the ganglion, and enkephalin-immunoreactive preganglionic neurons; the colonic nerves carry vasoactive intestinal polypeptide-, cholecystokinin- and bombesin-immunoreactive fibers from the distal colon to the ganglion; the hypogastric nerves contain vasoactive intestinal polypeptide-positive fibers from the pelvic plexus; and the intermesenteric nerve contains vasoactive intestinal polypeptide, cholecystokinin, substance P and enkephalin from divergent sources. By studying accumulations of peptides in ligated lumbar splanchnic, intermesenteric, hypogastric and colonic nerves the existence of these major peptidergic pathways was confirmed and evidence was obtained for additional, not so prominent, peptidergic projections. The results arae discussed in view of earlier morphological and physiological studies.

The origins, pathways and terminations of neurons with VIP-like immunoreactivity in the guinea-pig small intestine

We have analyzed changes in the distributions of terminals with vasoactive intestinal polypeptide (VIP)-like immunoreactivity, and accumulations in severed processes, that occur after lesions of intrinsic and extrinsic nerve pathways of the guinea-pig small intestine. The observations indicate that enteric vasoactive intestinal polypeptide immunoreactive neurons have the following projections. Nerve cell bodies in the myenteric plexus provide varicose processes to the underlying circular muscle; the majority of these pathways, if they extend at all in the anal or oral directions, do so for distances of less than 1 mm. Nerve cell bodies of the myenteric plexus also project anally to provide terminals to other myenteric ganglia. The lengths of the majority of these projections are between 2 and 10 mm, with an average length of about 6 mm. Processes of myenteric neurons also run anally in the myenteric plexus and then penetrate the circular muscle to provide varicose processes in the submucous ganglia at distances of up to 15 mm, the average length being 9-12 mm. In addition, there is an intestinofugal projection of myenteric neurons whose processes end around nerve cell bodies of the coeliac ganglia. A similar projection from the colon supplies the inferior mesenteric ganglia. The nerve cell bodies in submucous ganglia give rise to a subepithelial network of fibres in the mucosa and also supply terminals to submucous arterioles. It is concluded that vasoactive intestinal polypeptide is contained in neurons of a number of intrinsic nerve pathways, influencing motility, blood flow and mucosal transport. The myenteric neurons that project to prevertebral sympathetic ganglia may be involved in intestino-intestinal reflexes.

Cholecystokinin-immunoreactive neurons in rat and monkey cerebral cortex make symmetric synapses and have intimate associations with blood vessels

Neurons displaying cholecystokinin-like immunoreactivity (CCK neurons) in rat and monkey cerebral cortex were examined by light and electron microscopic immunocytochemistry. CCK neurons were found to be mainly bipolar cells present in all layers and in all areas of the rat cerebral cortex. CCK neurons were also found in all regions examined in monkey cortex (pre- and post-central gyri and superior parietal lobule). The somata and the dendritic processes of CCK neurons receive relatively few synapses but both symmetric and asymmetric axosomatic and axodendritic synapses were found. The majority of axon terminals displaying CCK-like immunoreactivity formed symmetric synapses, most frequently with the somata and proximal dendrites of pyramidal and nonpyramidal neurons. The somata and processes of CCK neurons were also found to establish very close nonsynaptic associations with blood vessels and with other neurons, suggesting possible roles for the peptide in the maintenance of neuronal excitability and cerebral blood flow.

Quinacrine-induced degeneration of non-adrenergic, non-cholinergic autonomic nerves in the rat anococcygeus muscle

The morphological changes induced in the autonomic nerves of the rat anococcygeus muscle after the injection of quinacrine (QC, 100 or 200 mg/kg) were examined by electron microscopy in order to clarify the nature of QC-binding nerves seen at the fluorescence-microscopic level. A correspondence between granular QC fluorescence and many lysosomal dense bodies is observed both in the cytoplasm of muscle cells and in non-adrenergic, non-cholinergic (NANC) axons during the first few days following injection. A number of brilliantly fluorescent fibres is observed 1 week after injection. At the ultrastructural level, these fibres seem to correlate with NANC axons which are crowded with many dense bodies and large granular vesicles. Notably, some lysosomal dense bodies contain many large granular vesicles. The effects of QC injection on the ultrastructure of adrenergic axons have also been observed, but are not so marked as in the NANC axons. The administration of QC did not cause complete degeneration of the NANC nerves, though degenerating axons were sometimes observed. The present data indicate that most, if not all, QC-binding nerves observed at the fluorescence-microscopic level correspond to NANC nerves at the electron-microscopic level. Furthermore, NANC axons appear to contain a considerable amount of ATP concentrated in the large granular vesicles.

The Vibratome-Ralph knife combination: a useful tool for immunohistochemistry

A modified immunohistochemical technique is described for the improved detection of antigens. The method involves the use of the Vibratome combined with Ralph knives, which are easily manufactured with an LKB 2078 Histoknifemaker. The sectioning procedure was used with the peroxidase-antiperoxidase method of Sternberger and his collaborators for demonstrating growth hormone release-inhibiting hormone (somatostatin) and noradrenaline N-methyltransferase in neurones in the central nervous system of the rat. The morphological preservation of the tissue was good and cytological details were easily seen, especially in the thin sections (5-10 microns thick).

Localization of vasoactive intestinal polypeptide- and avian pancreatic polypeptide-like immunoreactivity in the Golgi apparatus of peripheral neurons

Using the indirect immunofluorescence technique of Coons and collaborators, vasoactive intestinal polypeptide (VIP)-like immunoreactivity (VIP-LI) and avian pancreatic polypeptide (APP)-like immunoreactivity (APP-LI) was observed in certain neurons of the peripheral nervous system of the cat. In the cell bodies in the cat sympathetic ganglia a strong to very strong VIP-LI or APP-LI was observed with a distribution resembling that of the Golgi apparatus. In addition, a weaker immunoreactivity was seen diffusely in the cytoplasm. After photography, the sections processed for immunohistochemistry were stained with the thiamine pyrophosphatase technique of Novikoff and Goldfischer. The latter technique is assumed to be a specific marker for the Golgi complex. In all cases it was found that the strong peptide immunoreactivity and the thiamine pyrophosphatase activity had an identical distribution. Thus, one pool of these peptides appears to be localized to the Golgi apparatus. Yet another pool is localized to other components, such as vesicles.

The adrenal chromaffin cell as a model to study the co-secretion of enkephalins and catecholamines

The enkephalins, endogenous opioid pentapeptides first discovered in brain, are present in high concentrations in the adrenal medulla chromaffin cell. The enkephalins and other peptides containing enkephalin sequences are stored with catecholamines in the secretory organelles (chromaffin vesicles); these peptides are apparently incorporated into the vesicles at the time of their biosynthesis as opposed to later accumulation, as is the case with catecholamines. The enkephalins, catecholamines and other soluble components of the vesicle are co-secreted by the process of exocytosis. Regulatory mechanisms, apparently triggered by a critical catecholamine pool, control the synthesis of enkephalins. These mechanisms allow for rapid recovery of enkephalin content after secretion. These findings have been extended from the chromaffin cell to the ontogenically related sympathetic neurons and pheochromocytoma tumors. Secreted enkephalins and related peptides reach ubiquitous opiate receptors through the synaptic gap or the circulation and may modulate a number of important systemic functions. The co-storage and co-secretion of adrenomedullary opioid peptides and catecholamines is only one of a growing number of examples of co-existence of multiple messengers in single neuronal or endocrine cell types. Co-secreted multiple messengers may act in a co-ordinated fashion to produce integrated organismal responses.

The cholinergic innervation of human pancreatic islets

The cholinergic innervation of pancreatic islets was investigated in the human using operatory samples. In order to analyze the nature of stained cholinergic nerve fibers some specimens were incubated in a solution containing 6-hydroxydopamine (6-HDA) to obtain a selective degeneration of adrenergic nerves. Cholinergic nerve fibers are present in human pancreatic islets, and appear to be organized in an external peri-insular plexus. Some nerve fibers from the peri-insular plexus enter the islets and seem to innervate directly various types of endocrine insular elements. The 6-HDA treatment does not alter the distribution pattern of cholinergic nerve fibers within pancreatic islets.

Innervation of the mucosa of rabbit maxillary sinus. II. Demonstration of catecholamine fluorescence and acetylcholinesterase activity

The innervation of the rabbit maxillary sinus mucosa has been studied with histochemical techniques, using the glyoxylic acid-induced fluorescence for the demonstration of catecholamines and the acetylcholinesterase method. A dense acetylcholinesterase-positive nerve plexus can be demonstrated around the secretory end-pieces, the efferent ducts, the blood vessels in the lamina propria, and rarely but regularly in the ciliated epithelium. A doubtless identification of these nerve fibres to be cholinergic does not seem possible. The adrenergic innervation is lacking within the epithelium, but can be seen near the muscle layers around blood vessels and in the lamina propria. An additional sympathetic control of the glandular activity is not excluded.

Regulation of cyclic AMP accumulation in a rat sympathetic ganglion: effects of vasoactive intestinal polypeptide

Cyclic AMP accumulation in rat superior cervical ganglia during synaptic activity occurs by a noncholinergic, nonadrenergic process. Both preganglionic nerve stimulation and 4-aminopyridine increase ganglion cyclic AMP levels in the presence of atropine or phentolamine. Of the polypeptides tested as putative transmitters, vasoactive intestinal polypeptide (10(-6) M) causes ganglion cyclic AMP accumulation comparable to that produced by preganglionic nerve stimulation.

Further evidence for a muscarinic component to the neural vasodilator innervation of cerebral and cranial extracerebral arteries of the cat

Transmural electrical stimulation of segments of lingual and cerebral (basilar, middle and posterior cerebral) and also other cranial arteries of the cat results after a long latency in a dilator response. The response may be resolved into two components--an initial transient atropine-sensitive component and a slower more ponderous one that is atropine-resistant. The variability in pattern of dilation responses from segments of different vessels or even those from the same segment of different cats is considerable. Some responses are entirely atropine-sensitive and others atropine-resistant; however the vast majority show a dilation that can be considered to be made up of both components. The latencies of the atropine-sensitive and atropine-resistant components are not different. The effect of atropine on the lingual but not the cerebral arteries is frequency dependent, being proportionately greater at low than at high frequencies. In both vessels, the effect of atropine is independent of train length at 1 Hz. Physostigmine potentiates significantly the dilation of the lingual artery but not that of the cerebral arteries. The potentiation is reversed by atropine. The endogenous acetylcholine level was measured in a series of vessels. It can be correlated with the activity of choline acetyltransferase and the presence of neurogenic dilation. It is proposed that there are two transmitters released in parallel from nerve(s) in the walls of cerebral, lingual, and possibly, other cranial arteries to cause vasodilation. It seems that one of these is acetylcholine.

Somatostatin is contained in and released from cholinergic nerves in the heart of the toad Bufo marinus

The heart of the toad Bufo marinus contained a substance with somatostatin-like immunoreactivity which eluted with somatostatin on reverse phase high pressure liquid chromatography. Immunoreactivity to somatostatin was localised histochemically to nerve fibers in muscle bundles of the sinus venosus, atria and ventricles and to nerve cell bodies in the sinus venosus and inter-atrial septum. Nerve cell bodies were localised both by interference contrast microscopy and immunohistochemistry; all detectable intracardiac neurons were immunoreactive. Synthetic somatostatin inhibited the rate and force of beat of atrial preparations, but did not affect the driven ventricle. Vagal stimulation caused inhibition of all cardiac chambers. After muscarinic blockade with hyoscine, vagal stimulation with 3 Hz or more still caused inhibition of the pacemaker and atrium, but not of the ventricle. The hyoscine-resistant vagal effects were diminished by about 60% after induction of tachyphylaxis to somatostatin. When when the vagus nerves were stimulated intermittently for 1 h at 10 Hz, in the presence or absence of hyoscine, the effect of somatostatin was reduced by about 60%. It is concluded that the cholinergic postganglionic neurons of the cardiac vagus contain somatostatin. When the vagus is stimulated at 3 Hz or more, the neurons release sufficient somatostatin to inhibit the pacemaker and atrial muscle.

Mapping, quantitative distribution and origin of substance p- and VIP-containing nerves in the uvea of guinea pig eye

VIP- and substance P-like immunoreactivities were found in considerable concentrations (VIP: 17.3 +/- 4.8 pmol/g, mean +/- SEM; substance P:11.1 +/- 1.8 pmol/g) in the uveal portion of the guinea pig eye. Immunocytochemistry localised these two regulatory peptides to nerve fibres found principally in a plexus in the iris (substance P) and in an extensive network surrounding the blood vessels of the choroid (VIP). A remarkable anatomical demarcation of the two types of peptide-containing nerves was established by the staining of substance P-containing nerves, which stops at the level of the ciliary body. This uveal area is known to be involved in the ocular responses to nociceptive stimuli. At the ultrastructural level, immunoreactivity for both peptides was localised to distinct subpopulations of p-type nerves, distinguishable by the size of their large dense-cored vesicles. Those immunoreactive for VIP were significantly larger (p less than 0.0005) than those immunoreactive for substance P (95 +/- 7 nm and 82 +/- 9 nm respectively; mean +/- SD). Interruption of the trigeminal pathway produced a remarkable decrease of substance P immunoreactivity in the anterior portion of the uvea (9.1 +/- 1.5 pmol/g, mean +/- SEM, control; 5.3 +/- 1.3 pmol/g, denervated), but not of VIP immunoreactivity in the choroid. Following colchicine treatment, VIP-immunoreactive neuronal cell bodies were localised in the choroid. The separate anatomical localisations and distributions of the two uveal peptides appear to be related to their different origins and functional roles in the response of the eye to noxious stimuli.

Enkephalin-containing sympathetic preganglionic neurons projecting to the inferior mesenteric ganglion: evidence from combined retrograde tracing and immunohistochemistry

The origin of fibers containing enkephalin immunoreactivity in the inferior mesenteric ganglion of the guinea-pig was studied by combining retrograde axonal tracing and indirect immunofluorescence techniques. Fast Blue was applied into the inferior mesenteric ganglion. Three days later colchicine was administered into the subarachnoid space in order to increase the peptide content of the spinal cord cell bodies. The drug was injected through a catheter which was inserted into the cisterna magna and moved to the appropriate spinal cord levels. After the colchicine injection the animals were perfused with formalin and the L2-L3 spinal cord segments were dissected. Cryostat sections of the spinal cord were analyzed in a fluorescence microscope and subsequently processed for indirect immunohistochemistry using antiserum against enkephalin. Several sympathetic preganglionic neurons containing both Fast Blue and enkephalin-like immunoreactivity were seem mainly in the intermediolateral cell column of the cord. The observations strongly support the view that at least some of the enkephalin-containing fibers in the inferior mesenteric ganglion originate in the sympathetic preganglionic nuclei of the spinal cord. These findings are discussed in view of recent physiological studies which have shown that enkephalin may have a presynaptic inhibitory action on preganglionic neurons as well as on substance P containing primary afferent neurons in the inferior mesenteric ganglion.

Neuropeptides in sensory neurons

Substance P, somatostatin, VIP, CCK, angiotensin II, and bombesin have all been localized by immunohistochemical or radioimmunological means in neurons of sensory ganglia or in the dorsal horn of the spinal cord. Most of these neuropeptides have electrophysiological effects on spinal neurons and for substance P and somatostatin, these effects have been associated with particular sensory modalities. Newer investigations using the compound capsaicin are consistent with the hypothesis that substance P is an important neurochemical mediator of certain kinds of noxious peripheral stimuli. The newly described substance P antagonists promise to be important pharmacological tools for investigation of the long-neglected neurochemical bases of sensory neuron function. Elaboration of the roles of these sensory neuropeptides will no doubt shed light on many disease states in which there seems to be sensory neuron involvement.

Immunogold staining procedure for the localisation of regulatory peptides

The use of protein A- and IgG-conjugated colloidal gold staining methods for the immuno-localisation of peptide hormones and neurotransmitters at light- and electron microscope level are described and discussed. Bright-field and dark-ground illumination modes have been used to visualise the gold-labelled antigenic sites at the light microscope level. Immunogold staining procedures at the ultrastructural level using region-specific antisera have been adopted to localise specific molecular forms of peptides including gastrin (G17 and G34), glucagon and pro-glucagon, insulin and pro-insulin, in normal tissue and in tumours of the gastroenteropancreatic system. Similar methods have been used to demonstrate the heterogeneity of p-type nerves in the enteric nervous system. Vasoactive intestinal polypeptide (VIP) has been localised to granular sites (mean +/- S.D. granule diameter = 98 +/- 19 nm) in nerve terminals of the enteric plexuses and in tumour cells of diarrhoeogenic VIP-producing neoplasias (mean +/- S.D. granule diameter = 126 +/- 37 nm) using immunogold procedures applied to ultraviolet-cured ultrathin sections. Co-localisation of amines and peptides in carotid body type I cells and in chromaffin cells of normal adrenal medulla and phaeochromocytomas has also been demonstrated. Advantages of the immunogold procedures over alternative immunocytochemical techniques are discussed.

Structural studies on the connectivity of the inferior mesenteric ganglion of the guinea pig

After injection of horseradish peroxidase (HRP) into the inferior mesenteric ganglion (IMG) of the guinea pig, labeled cell bodies were found in the solar plexus ganglia, the ganglia of the pelvic plexus and in the nodose ganglia as well as in the spinal cord and dorsal root ganglia at the T13-L4 levels. By using the fluorescent tracer True blue, labeled cell bodies could also be detected in the myenteric and submucosa ganglia of the distal colon. Application and uptake of HRP by the colonic nerves resulted in labeling of cell bodies in the dorsal root ganglia, the IMG and in the solar plexus ganglion complex indicating that the latter neurons send their axons in the intermesenteric nerve through the IMG to continue in the colonic nerves to the distal colon. When HRP was applied and diffused into the hypogastric nerves labeled cell bodies were seen in the IMG, the dorsal root ganglia and in the preganglionic nuclei of the lumbar spinal cord with 50% of the labeled neurons located dorsal and dorsolateral to the central canal. The finding of such a diversity in the nerve supply to the IMG, supports the view that the ganglion plays an important role in the integration of visceral reflexes.

Distribution of choline acetyltransferase in cerebral and extracerebral cranial arteries of the cat. Its relationship to neurogenic atropine-sensitive dilation

Choline-acetyltransferase (ChAT) activity was surveyed in segments of cranial arteries--both cerebral and extracerebral--from the cat. High levels were found in pial arteries, both cerebral and cerebellar, and in the arteries to salivary glands, tongue, and nose. Intermediate levels were found in the external and internal maxillary arteries and many of their branches. Enzyme levels in the arteries supplying the head--common carotid, vertebral, and in several systemic arteries and veins and also the lingual vein--were probably not significant. Only those vessels that have higher ChAT contents show capacity for neurogenic vasodilation. The dilation of segments of a number of these arteries, the basilar, middle cerebral, lingual, and internal maxillary, is reduced significantly by atropine (5 X 10(-7) M). ChAT activity did not correlate with vessel norepinephrine content. The data may be interpreted as defining a functional vasodilator system to the head encompassing both cerebral and extracerebral arteries that depends in part on a functional cholinergic link involving a muscarinic receptor. It is separate from the adrenergic outflow. The tissues supplied by vasculature receiving this type of innervation are of ectodermal origin.

The effects of purified botulinum neurotoxin type A on cholinergic, adrenergic and non-adrenergic, atropine-resistant autonomic neuromuscular transmission

The twitch response observed during low frequency electrical stimulation of postganglionic cholinergic neurones supplying the longitudinal smooth muscle of the guinea-pig ileum was markedly reduced by incubation with an homogeneous preparation of botulinum type A neurotoxin (4.3-8.6 nM). This intoxication of the autonomic cholinergic neurones was long-lasting, irreversible by washing, but readily reversed by 4-aminopyridine (50-1000 microM). The noradrenergic motor response of the rat anococcygeus following field stimulation was partially antagonised by the neurotoxin. The non-adrenergic inhibitory response of the guinea-pig taenia coli, elicited by field stimulation, was not antagonised by botulinum toxin, suggesting that a source of a non-adrenergic inhibitory transmitter exists, other than intramural cholinergic neurones. However, the neurogenic excitatory responses of the guinea-pig bladder, elicited by field stimulation in the presence of atropine and guanethidine, were virtually abolished by botulinum toxin. It is suggested that the parasympathetic neurones which supply the smooth muscle of the guinea-pig urinary bladder co-release acetylcholine and a non-cholinergic excitatory transmitter; ATP or polypeptides are possible candidates.

Vasoactive intestinal polypeptide (VIP) in the medulla oblongata of the guinea pig

Using the peroxidase-antiperoxidase (PAP) technique brains of colchicine-treated guinea pigs were investigated for the occurrence of vasoactive intestinal polypeptide-like immunoreactive (VIP-IR) neurons. VIP-IR perikarya were found not only in previously documented areas of the cortex, hypothalamus and substantia grisea centralis, but also in the nucleus nervi vagi, nucleus solitarius and the formatio reticularis.

Coexistence of somatostatin- and avian pancreatic polypeptide (APP)-like immunoreactivity in some forebrain neurons

The indirect immunofluorescence technique was used to demonstrate the coexistence of somatostatin together with avian pancreatic polypeptide-like immunoreactivity within certain neurons of the rat forebrain. Numerous neurons containing these peptides were observed in the neocortex, hippocampus, olfactory tubercle, striatum, nucleus accumbens and lateral septum. In studies of serial sections stained alternately for these two peptides, and in restaining experiments, It could be determined that in many neurons in these areas these two peptides coexisted. In other brain areas such as the anterior periventricular hypothalamus, somatostatin cells were never found to contain avian pancreatic polypeptide-like immunoreactivity. Also, within the pancreas these two peptides were never found to coexist in the same cells. The findings represent a further example of the coexistence of more than one neuropeptide within a single neuron.