Mixed venous oxygen saturation is a prognostic marker after surgery for aortic stenosis.

BACKGROUND: Adequate monitoring of the hemodynamic state is essential after cardiac surgery and is vital for medical decision making, particularly concerning hemodynamic management. Unfortunately, commonly used methods to assess the hemodynamic state are not well documented with regard to outcome. Mixed venous oxygen saturation (SvO(2)) was therefore investigated after cardiac surgery. METHODS: Detailed data regarding mortality were available on all patients undergoing aortic valve replacement for isolated aortic stenosis during a 5-year period in the southeast region of Sweden (n=396). SvO(2) was routinely measured on admission to the intensive care unit (ICU) and registered in a database. A receiver operating characteristics (ROC) analysis of SvO(2) in relation to post-operative mortality related to cardiac failure and all-cause mortality within 30 days was performed. RESULTS: The area under the curve (AUC) was 0.97 (95% CI 0.96-1.00) for mortality related to cardiac failure (P=0.001) and 0.76 (95% CI 0.53-0.99) for all-cause mortality (P=0.011). The best cutoff for mortality related to cardiac failure was SvO(2) 53.7%, with a sensitivity of 1.00 and a specificity of 0.94. The negative predictive value was 100%. The best cutoff for all-cause mortality was SvO(2) 58.1%, with a sensitivity of 0.75 and a specificity of 0.84. The negative predictive value was 99.4%. Post-operative morbidity was also markedly increased in patients with a low SvO(2). CONCLUSION: SvO(2), on admission to the ICU after surgery for aortic stenosis, demonstrated excellent sensitivity and specificity for post-operative mortality related to cardiac failure and a fairly good AUC for all-cause mortality, with an excellent negative predictive value.

A substance P antagonist, [D-Pro2, D-Trp7,9]SP, inhibits inflammatory responses in the rabbit eye.

Neurogenic factors released by antidromic nerve stimulation are thought to be in part responsible for the vasodilation and breakdown of the blood-aqueous barrier that follows trauma to the eye. Substance P is one candidate for the mediation of the inflammatory response since it is thought to be a neurotransmitter in sensory afferents and since exogenous substance P is capable of eliciting a response characteristic of inflammation. In rabbits, intravitreal or topical application onto the eye of a specific substance P antagonist, [d-Pro2, D-Trp7,9]SP, inhibited not only the irritant effects of exogenous substance P but also the inflammatory response to a standardized trauma (infrared irradiation of the iris). These observations suggest that substance P, or a related peptide, is a neurogenic mediator of the inflammatory response in the eye.

Tachyphylaxis of the ECL-cell response to PACAP: receptor desensitization and/or depletion of secretory products.

BACKGROUND AND PURPOSE: Rat stomach ECL cells secrete histamine and pancreastatin in response to gastrin and pituitary adenylate cyclase-activating peptide-27 (PACAP). This study applies microdialysis to explore how ECL cells in situ respond to PACAP and gastrin. EXPERIMENTAL APPROACH: Both peptides were administered by microinfusion into the gastric submucosa. The microdialysate was analysed for histamine and pancreastatin (ECL-cell markers) and for somatostatin (D-cell marker). KEY RESULTS: Microinfusion of PACAP (0.01-0.3 nmol microl(-1)) raised microdialysate histamine and pancreastatin dose-dependently. The response was powerful but short-lived. The response to gastrin was sustained at all doses tested. It is unlikely that the transient nature of the histamine response to PACAP reflects inadequate histamine synthesis, since the pancreastatin response to PACAP was short-lived too, and both gastrin and PACAP activated ECL-cell histidine decarboxylase. Unlike gastrin, PACAP mobilized somatostatin. Co-infusion of somatostatin abolished the histamine-mobilizing effect of PACAP. However, pretreatment with the somatostatin receptor type-2 antagonist (PRL-2903) did not prolong the histamine response to PACAP, suggesting that mobilization of somatostatin does not explain the transient nature of the response. Repeated administration of 0.1 nmol microl(-1) of PACAP (1 h infusions, 1 h intervals) failed to induce a second histamine response. Pretreatment with a low dose of PACAP (0.03 nmol microl(-1)) abolished the response to a subsequent near-maximal PACAP challenge (0.3 nmol microl(-1)). CONCLUSION: The transient nature of the histamine response to PACAP reflects desensitization of the PACAP receptor and/or exhaustion of a specific storage compartment that responds to PACAP but not to gastrin.

Neuropeptide Y effector systems: perspectives for drug development.

Neuropeptide Y was isolated in 1982 and has since attracted considerable interest. It is widely distributed in central and peripheral neurones and can produce a multitude of biological effects in the brain and the periphery. For example, the peptide has been associated with stimulation of food and water intake, control of mood, and regulation of central autonomic functions. In the periphery, sympathetic neuropeptide Y plays a role as a vasopressor and vasoconstrictor. Neuropeptide Y acts on at least three distinct receptor types, referred to a Y1, Y2 and Y3. This review by Lars Grundemar and Rolf Håkanson focuses on some neuropeptide Y-dependent mechanisms that may be implicated in certain disorders and may be promising targets for drugs active at neuropeptide Y receptors.

Production and characterization of rabbit antibodies against histamine.

Antisera were raised in rabbits against histamine conjugated to human serum albumin (HSA) by the carbodiimide (ECDI) method. The specificity of the antisera was studied in a radioimmunoassay using 125I-protein A for detection of IgG binding. The HIS-HSA antisera reacted with histamine-HSA conjugates prepared by either the carbodiimide or diisocyanate coupling procedure, as well as with carbodiimide-prepared histamine-ferritin and histamine-ovalbumin conjugates. On the contrary, the antisera were unreactive with unconjugated HSA, ECDI-reacted HSA, or HSA conjugated to ethanolamine or pentylamine. Free unconjugated histamine significantly inhibited antibody binding to histamine-HSA and 50% inhibition of antibody binding (IC50) was recorded at 3 mM histamine concn. On a histamine molar concn basis a much lower inhibitory potency of free histamine was recorded, as compared to histamine-protein conjugates (IC50 = 3 X 10(-6) mM). This probably reflected amplification of antibody binding to the multivalent ligand, but possibly also that the protein carrier adds some common features to the antigenic determinant. Histidine, ornithine, glutamine, asparagine, sterylamine and several other amino acids lacked inhibitory effects. Histamine H1 and H2 receptor antagonists inhibited histamine binding to the histamine antibodies. The antagonists varied in their affinity for the histamine antibodies and 50% inhibition of antibody binding was recorded in the range of 1-50 mM concn of the antagonists. Comparing one H1 and one H2 antagonist (diphenhydramine and cimetidine, respectively) two of the sera were preferentially inhibited by cimetidine whereas the third serum seemed to be more prone to inhibition by diphenhydramine.

Neurokinin A and galanin in the thyroid gland: neuronal localization.

The distribution of neurokinin A (NKA) and galanin (GAL) in the thyroid gland of several species was examined with immunocytochemistry. NKA-immunoreactive fibers were observed around blood vessels and follicles in all species examined, whereas GAL-immunoreactive fibers were found in mice and rats only. NKA-containing fibers were more numerous than GAL-containing fibers. All thyroid NKA-containing fibers harbored substance P (SP), and the majority of them stored calcitonin gene-related peptide (CGRP) as well. Most thyroid GAL-immunoreactive fibers contained NKA, SP, and CGRP; in a minor population GAL coexisted instead with vasoactive intestinal peptide. Cervical vagotomy (extirpation of the nodose ganglion) reduced the number of NKA- and GAL-containing fibers in the thyroid by approximately 50%. The jugular ganglion and cervical dorsal root ganglia are fairly rich in GAL-, NKA/SP-, and CGRP-containing cell bodies, which presumably represent the source of GAL-, NKA/SP-, and CGRP-containing fibers in the thyroid. The thyroid ganglion is rich in vasoactive intestinal peptide nerve cell bodies, which presumably project to the thyroid gland; a minor proportion of these cell bodies was found to contain GAL as well. Although the distribution of NKA and GAL fibers in the thyroid suggests that the two peptides are involved in the regulation of local blood flow and follicular cell activity, neither NKA nor GAL had any influence on thyroid hormone release as tested in conscious mice.

Neuropeptide Y in the thyroid gland: neuronal localization and enhancement of stimulated thyroid hormone secretion.

Nerve fibers displaying neuropeptide Y (NPY) immunoreactivity occurred around blood vessels and follicles in the thyroid gland of several mammals, including man. Removal of the superior cervical ganglia or chemical sympathectomy (6-hydroxydopamine treatment) markedly reduced the number of NPY-containing nerve fibers in the thyroid and eliminated norepinephrine-containing fibers. NPY-immunoreactive nerve cell bodies were numerous in the superior cervical ganglia of mouse, rat, and guinea pig. Not unexpectedly, therefore, immunocytochemistry involving sequential staining with antibodies against dopamine-beta-hydroxylase (an enzyme marker for adrenergic neurons) and NPY revealed that most of the NPY fibers were adrenergic. As tested in mice in vivo, NPY did not affect basal or norepinephrine-stimulated thyroid hormone secretion, but enhanced isoprenaline-, TSH-, and vasoactive intestinal polypeptide-induced iodothyronine release. These findings suggest a modulatory role for NPY in the control of thyroid hormone secretion.

Radioimmunoassay of pro-gamma-melanotropin, the amino-terminal fragment of proopiolipomelanocortin.

A RIA has been developed for natural porcine pro-gamma MSH, the 103-amino acid peptide that represents the amino-terminal part of proopiolipomelanocortin. Rabbits were immunized with the purified peptide polymerized with glutaraldehyde. The antiserum is directed against the amino-terminal end of the antigen and does not cross-react with corticotropin, beta-lipotropin, beta-endorphin, gamma 3MSH, or gamma 2MSH. The minimum detectable concentration is 0.15 ng/ml standard pro-gamma MSH (15 pg/tube). Pro-gamma MSH-like immunoreactivity was detected in plasma and extracts of the hypothalamus and pituitary of pigs. Gel chromatography of these extracts revealed at least three immunoreactive peaks in the anterior and neurointermediate lobes of the pituitary, whereas two immunoreactive peaks were found in extracts of the hypothalamus.

Effects of gastrin on calcium homeostasis in chickens.

As in the rat, gastrin and an extract of the acid-producing part of the stomach (proventriculus) were found to lower the blood Ca2+ concentration in the chicken. Furthermore, gastrin enhanced the uptake of 45Ca into the femur. It has been suggested previously that gastrin causes hypocalcemia in the rat by releasing gastrocalcin, a hypothetical hormone thought to reside in the acid-producing part of the stomach. The results of the present study in the chicken are in agreement with this concept. Not only exogenous, but also endogenous gastrin lowered blood calcium levels. Thus, the serum gastrin concentration was increased in response to ranitidine-evoked blockade of the gastric acid output; the rise in gastrin was associated with a transient drop in blood calcium. Also, food intake produced a rise in the serum gastrin concentration and a transient drop in blood calcium. However, injection of ranitidine or food intake in proventriclectomized (acid-producing part of the stomach extirpated) chickens failed to lower blood calcium, supporting the view that the gastrin-evoked hypocalcemia depends upon an agent in the gastric (proventriculus) mucosa. We suggest that endogenous and exogenous gastrin evoke hypocalcemia in the chicken by the same mechanism as that which has been postulated in the rat, i.e. by mobilization of the candidate hormone gastrocalcin from endocrine cells in the acid-producing gastric mucosa.

Neuropeptides in the thyroid gland: distribution of substance P and gastrin/cholecystokinin and their effects on the secretion of iodothyronine and calcitonin.

Previously, vasoactive intestinal polypeptide was localized to intrathyroidal nerve fibers. It stimulates iodothyronine secretion in mice. In the present study two populations of nerve fibers containing substance P and gastrin/cholecystokinin (CCK)-like immunoreactivity, respectively, were demonstrated in the thyroid gland of several mammals. The substance P fibers occurred around blood vessels and follicles, whereas the gastrin/CCK fibers occurred mainly around follicles. In the chicken thyroid and ultimobranchial glands only substance P-containing fibers could be demonstrated. Such fibers were particularly numerous in the ultimobranchial gland. CCK-4, CCK-8, and substance P did not increase thyronine secretion measured as release of radioiodine into the circulation of mice pretreated with Na125I and T4. The TSH-induced release of radioiodine was also unaffected. Calcitonin secretion in rats was stimulated by CCK-4, CCK-8, substance P, and vasoactive intestinal polypeptide.

Peptide histidine isoleucine amide stimulates thyroid hormone secretion and coexists with vasoactive intestinal polypeptide in intrathyroid nerve fibers from laryngeal ganglia.

Peptide histidine isoleucine amide (PHI) and vasoactive intestinal polypeptide (VIP) are fragments of the same precursor molecule, prepro-VIP, and coexistence of the two peptides is, therefore, to be expected. Nerve fibers displaying PHI and VIP immunoreactivity occurred around blood vessels and follicles in the thyroid gland of several species. Sequential staining with antibodies against PHI and VIP revealed coexistence of the two peptides in the same population of nerve cell bodies in ganglia situated along the laryngeal nerves and in intrathyroid nerve fibers. Chemical sympathectomy (6-hydroxydopamine treatment), surgical sympathectomy (removal of the superior cervical ganglia), and unilateral cervical vagotomy (removal of the nodose ganglion) failed to affect the number and distribution of PHI/VIP fibers in the thyroid gland. Taken together, the findings suggest that both the perivascular and interfollicular PHI/VIP fibers originate in laryngeal ganglia. PHI weakly stimulated basal thyroid hormone secretion in mice in vivo, but did not influence the response to TSH or VIP. PHI had no effect on calcitonin secretion in rats. Like VIP, PHI may play a physiological role in the regulation of thyroid hormone secretion.

Calcitonin gene-related peptide in thyroid nerve fibers and C cells: effects on thyroid hormone secretion and response to hypercalcemia.

Calcitonin gene-related peptide (CGRP) in the thyroid has a dual localization to nerve fibers around blood vessels and follicles and to parafollicular (C) cells. CGRP was found to coexist with substance P (SP) in most of the nerve fibers; a few CGRP fibers seemed to lack SP, and a few SP fibers seemed to be devoid of CGRP. In the C cells, CGRP coexisted with calcitonin (CT). Cervical vagotomy (extirpation of the nodose ganglion) eliminated approximately 50% of the CGRP/SP fibers in the thyroid without any overt influence on CGRP/CT in the C cells. Removal of the superior cervical ganglion or chemical sympathectomy (6-hydroxydopamine treatment) affected neither thyroid CGRP/SP nerve fibers nor CGRP/CT-storing C cells. CGRP nerve cell bodies were numerous in the jugular-nodose ganglionic complex (notably in the jugular portion); in many of them, CGRP coexisted with SP. A few scattered CGRP nerve cell bodies also occurred in the laryngeal ganglion, whereas none was found in the thyroid ganglion. Hypercalcemia evoked by vitamin D2 treatment, which is known to degranulate thyroid C cells, reduced the thyroid content of both CGRP and CT. As tested in mice in vivo, CGRP and SP alone or together had no effect on basal or TSH- or isoprenaline-induced thyroid hormone secretion. Vasoactive intestinal peptide-stimulated iodothyronine release, on the other hand, was enhanced by CGRP, but not by SP. SP had no effect on combined vasoactive intestinal peptide-CGRP-stimulated iodothyronine release. These findings suggest that CGRP participates in the control of thyroid hormone secretion and that, like CT, CGRP in the C cells is under control of the serum calcium level.

Differential changes in the 5-hydroxytryptamine and insulin content of guinea-pig B-cells.

In the guinea-pig pancreas, 5-hydroxy-tryptamine (5-HT) occurs in the B-cells as well as in enterochromaffin cells scattered in the exocrine parenchyma. In the present study we examined the effects on the pancreatic 5-HT and insulin content of drugs known to affect the B-cells. For this purpose a radioimmunoassay of guinea-pig insulin was developed. Streptozotocin reduced the number of detectable B-cells and partially degranulated those that remained. It also lowered the insulin content of the pancreas and the 5-HT content of the B-cells but did not affect the 5-HT content of the enterochromaffin cells. Reserpine lowered the 5-HT content of both B-cells and enterochromaffin cells. The number and ultrastructure of the B-cells and the pancreatic insulin content was not affected. Streptozotocin + reserpine seemed to have additive effects of B-cell 5-HT. The results with these 2 drugs indicate that roughly 50% of pancreatic 5-HT is contained in the B-cells. Diazoxide markedly increased the pancreatic insulin content without affecting pancreatic 5-HT. Despite the fact that 5-HT and insulin are stored together in the cytoplasmic granules of the B-cells, 5-HT was differentially depleted from this store by reserpine. A marked disproportionality between 5-HT and insulin content was also induced by diazoxide.

Y1 and Y2 receptors for neuropeptide Y.

By using monoiodinated radioligands of both intact neuropeptide Y (NPY) and of a long C-terminal fragment, NPY13-36, two subtypes of binding sites, which differ in affinity and specificity, have been characterized. The Y1 type of binding site, characterized on a human neuroblastoma cell line, MC-IXC, and a rat pheochromocytoma cell line, PC-12, binds NPY with a dissociation constant (Kd) of a few nanomolar but does not bind NPY13-36. The Y2 type of binding site, characterized on porcine hippocampal membranes and on another human neuroblastoma cell line, SMS-MSN, is of higher affinity and binds both NPY and NPY13-36. None of the binding sites distinguish between NPY and the homologous peptide YY (PYY). It is concluded that NPY/PYY-binding sites occur in two subtypes which may represent two types of physiological receptors.

Return of nerve fibers containing gastrin-releasing peptide in rat small intestine after local removal of myenteric ganglia.

Gastrin-releasing peptide is a neuropeptide with a wide distribution in the rat small intestine. Most of the GRP-containing fibers are intramural in origin. Local severing of myenteric GRP neurons by circumferential removal of the outer longitudinal muscle layer together with the adherent myenteric ganglia (myectomy) in a segment of the rat jejunum resulted in the disappearance of GRP fibers from the myectomized circular muscle and from myenteric ganglia and both muscle layers for approximately 10 mm anally to the lesion. As examined at different time intervals up to 60 weeks postoperatively fine-varicose GRP fibers of a normal appearance were found to return gradually to the portion anal to the lesion beginning at 20 weeks, first in the more distal portions and then (after 40-60 weeks) also in the more proximally located portions. Also the circular muscle in the myectomized segment became reinnervated during this time period. These fibers were notably coarse, more numerous than in control circular muscle, and arranged in thick bundles (hyperinnervation). Such nerve bundles were particularly frequent 40 weeks after the operation. The results indicate a remarkable plasticity of enteric neurons.

Neuronal pathways to the rat thyroid revealed by retrograde tracing and immunocytochemistry.

The distribution and origin of the nerve fibres innervating the rat thyroid were studied by immunocytochemistry, retrograde tracing and denervation experiments. Immunocytochemistry revealed nerve fibres containing noradrenaline, neuropeptide Y, vasoactive intestinal peptide, peptide histidine-isoleucine, galanin, substance P, neurokinin A and calcitonin gene-related peptide around blood vessels and follicles. Many of these transmitter candidates were found to co-exist with each other in different combinations in different subpopulations of neurons. Sympathectomy eliminated all noradrenaline- and noradrenaline/neuropeptide Y-containing fibres in the thyroid. Cervical vagotomy eliminated about 50% of the galanin-, substance P- and calcitonin gene-related peptide-containing fibres. Local denervation (removal of the thyroid ganglion and the thyroid nerve) eliminated all galanin- and substance P-immunoreactive fibres and the majority of noradrenaline-, noradrenaline/neuropeptide Y-, vasoactive intestinal peptide- and calcitonin gene-related peptide-containing fibres in the thyroid gland. Injection of True Blue into the thyroid gland labelled cell bodies in the thyroid ganglion, the laryngeal ganglion, the superior cervical ganglion, the jugular-nodose ganglionic complex, the dorsal root ganglia (C2-C5) and the trigeminal ganglion. Judging from the number of labelled nerve cell bodies, the superior cervical ganglion and the thyroid ganglion contribute most to the thyroid innervation, while the laryngeal ganglion and the trigeminal ganglion contribute least. The True Blue-labelled ganglia were examined for the presence of various populations of nerve cell bodies (only major populations are listed). The thyroid ganglion harboured neuropeptide Y, vasoactive intestinal peptide and galanin/vasoactive intestinal peptide cell bodies (in order of predominance); the laryngeal ganglion galanin/vasoactive intestinal peptide, vasoactive intestinal peptide and calcitonin gene-related peptide cell bodies; the superior cervical ganglion noradrenaline/neuropeptide Y and noradrenaline cell bodies; the jugular ganglion calcitonin gene-related peptide, substance P/calcitonin gene-related peptide and galanin/substance P/calcitonin gene-related peptide cell bodies; the nodose ganglion vasoactive intestinal peptide and vasoactive intestinal peptide/galanin cell bodies; the dorsal root ganglia (C2-C5) and the trigeminal ganglion calcitonin gene-related peptide, substance P/calcitonin gene-related peptide and galanin/substance P/calcitonin gene-related peptide cell bodies.(ABSTRACT TRUNCATED AT 400 WORDS)

Galanin nerve fibers in the rat gut: distribution, origin and projections.

Galanin, a 29 amino acid peptide, was recently isolated from the porcine gut. Immunocytochemistry revealed a dense network of galanin-immunoreactive nerve fibers in the submucosa, smooth muscle layers and intramural ganglia throughout the rat gastrointestinal tract. In the smooth muscle the density of innervation was lower in the colon than in the small intestine. In the mucosa galanin-immunoreactive fibers were quite numerous in the small intestine, less numerous in the large intestine and rare in the stomach. A moderate number of galanin-immunoreactive nerve cell bodies could be detected in the myenteric ganglia throughout the digestive tract and in the submucous ganglia of the intestines. Enteric galanin-immunoreactive fibers seem to be intrinsic to the gastrointestinal tract since their distribution and frequency were unaffected after extrinsic denervation (chemical sympathectomy, vagal denervation or clamping of nerves running within the mesenterium). Myectomy at the mid-jejunal level resulted in a total loss of galanin-immunoreactive nerve fibers 5 mm anally to the lesion with a gradual return of galanin-immunoreactive fibers up to 15-20 mm further anally; there was no overt loss of fibers orally. The findings indicate that myenteric galanin-immunoreactive neurones issue long descending projections that terminate either within the myenteric ganglia or in the smooth muscle.

Projections of peptide-containing neurons in rat colon.

The distribution, origin and projections of nerve fibers containing vasoactive intestinal peptide, substance P, neuropeptide Y, galanin, gastrin-releasing peptide, calcitonin gene-related peptide, somatostatin or enkephalin were studied in the midcolon of the rat by immunocytochemistry and immunochemistry. Most of these nerve fibers had an intramural origin as was established by extrinsic denervation (serving of mesenterial nerves). Extrinsic denervation eliminated neuropeptide Y-containing fibers of presumably sympathetic origin together with sensory nerve fibers containing both substance P and calcitonin gene-related peptide. Co-existence of two peptides in the same neuron was studied by double immunostaining. This revealed co-existence of neuropeptide Y and vasoactive intestinal peptide in one population of intramural neurons; an additional population of intramural neurons was found to contain vasoactive intestinal peptide but not neuropeptide Y. All somatostatin-containing neurons in the submucous ganglia were found to harbor calcitonin gene-related peptide. A much larger population of submucous neurons containing calcitonin gene-related but not somatostatin was also detected. Some perivascular calcitonin gene-related peptide-containing nerve fibers (of intrinsic origin) harbored vasoactive intestinal peptide while others (of extrinsic origin) harbored substance P. The polarities and projections of the various peptide-containing intramural neurons in the transverse colon were studied by analysing the loss of nerve fibers upon local disruption of enteric nervous pathways (myectomy or intestinal clamping). Myenteric neurons containing vasoactive intestinal peptide, galanin, gastrin-releasing peptide, calcitonin gene-related peptide, somatostatin or vasoactive intestinal peptide/neuropeptide Y gave off 5-10-mm-long descending projections while those containing substance P or enkephalin issued approx. 5-mm-long ascending projections. Submucous neurons containing calcitonin gene-related peptide, somatostatin/calcitonin gene-related peptide or gastrin-releasing peptide issued both ascending (2-6 mm) and descending (2-6 mm) projections, those containing vasoactive intestinal peptide issued ascending (approx. 2 mm) projections, while those containing galanin or vasoactive intestinal peptide/neuropeptide Y lacked demonstrable oro-anal projections. Enkephalin-containing fibers could not be detected in the mucosa and the mucosal substance P-containing nerve fibers were too few to enable us to delineate their projections.

Distribution and effects of pituitary adenylate cyclase-activating peptide in the rabbit eye.

Pituitary adenylate cyclase-activating peptide (PACAP)-like immunoreactivity was demonstrated by immunocytochemistry together with calcitonin gene-related peptide (CGRP)-like immunoreactivity in small to medium-sized neurons in the trigeminal ganglion and in nerve fibers in the iris, ciliary body, cornea, choroid and sclera of the rabbit eye. The regional distribution of PACAP-27- and PACAP-38-like immunoreactivity in the eye was studied by radioimmunoassay: the highest concentrations were found in the iris sphincter and ciliary body. The distribution pattern resembled that of CGRP-like immunoreactivity, which is a well-known constituent of sensory C-fibre neurons. Intravitreal injection of PACAP-27 or PACAP-38 induced conjunctival hyperemia, swelling of the anterior segment of the eye, miosis and breakdown of the blood-aqueous barrier, manifested as a marked aqueous flare response. Tetrodotoxin pretreatment inhibited the conjunctival hyperemia, the swelling of the anterior segment of the eye, and the miosis but not the aqueous flare response. The concentration of PACAP-like immunoreactivity in the aqueous humor was increased greatly following infrared irradiation of the iris, topical application of formaldehyde to the cornea, or intravitreal injection of endotoxin or bovine serum albumin. Also the concentration of CGRP-like immunoreactivity in the aqueous humor was increased greatly. Both in vivo and in vitro studies showed that capsaicin caused a parallel release of PACAP-like immunoreactivity and CGRP-like immunoreactivity from the uvea. Injection of PACAP-27 and PACAP-38 resulted in the release of CGRP-like immunoreactivity (and PACAP-like immunoreactivity) into the aqueous humor and PACAP-27 and PACAP-38 were also found to evoke tachykinin-mediated contractions of the isolated iris sphincter muscle, indicating that PACAP induces positive feedback on C-fibres. Thus, PACAP is a sensory neuropeptide in the eye. Since the PACAP-induced ocular responses mimicked the symptoms of inflammation, and since the PACAP-like immunoreactivity concentration in the aqueous humor was greatly increased following noxious stimulation, we suggest that it takes part in the inflammatory responses of the rabbit eye.

Helodermin- and helospectin-like immunoreactivities in the rat brain: an immunochemical and immunohistochemical study.

Helodermin is an amidated peptide of 35 amino acid residues isolated from the lizard Heloderma suspectum. Homologous peptides, helospectins I and II, peptides of 38 and 37 amino acid residues, respectively, have been isolated from the lizard Heloderma horridum. This group of peptides stimulates the adenylate cyclase activity. Helodermin- and helospectin-like immunoreactivities were studied in the rat brain by using immunohistochemistry and radioimmunoassay in combination with high-performance liquid chromatography. The highest concentrations of helodermin-like immunoreactivity were found in the cerebellum and hypothalamus. The chromatographic analysis of rat brain extract revealed one main immunoreactive peak with elution properties similar to those of authentic lizard helodermin. Helodermin-immunoreactive neurons were located in the supraoptic nucleus, suprachiasmatic nucleus, periventricular nucleus, arcuate nucleus and central gray. Fibers and terminals of varying densities were observed in the bed nucleus of the stria terminalis, medial part of the central nucleus of amygdala, external layer of the median eminence, thalamus and central gray. The highest concentrations of helospectin-like immunoreactivity were found in the cerebral cortex, hypothalamus and medulla. The chromatographic analysis of brain extract revealed one major peak with elution properties similar to those of authentic helospectin I. Helospectin-immunoreactive neurons were located in the suprachiasmatic nucleus, central gray, cerebral cortex, dorsomedial hypothalamic nucleus and supramammillary nucleus. Helospectin-immunoreactive fibers and terminals were found in the bed nucleus of the stria terminalis, medial part of the central nucleus of amygdala, median eminence, lateral parabrachial nucleus, central gray, cerebral cortex, thalamus and nucleus of the solitary tract. The present study has revealed novel neuronal systems in the rat brain by using antisera against the lizard peptides helodermin and helospectin. The patterns of immunostaining suggest a role for the helodermin- and helospectin-like peptides in the hypothalamo-hypophyseal control of endocrine functions.