Distribution and characterization of pedal peptide immunoreactivity in Aplysia

Pedal peptide (Pep) is a very abundant neuropeptide in Aplysia. A radioimmunoassay (RIA) was developed to quantify Pep-like immunoreactivity (IR-Pep) in tissue extracts. IR-Pep was present in very high concentrations in the central nervous system (CNS) and two peripheral tissues: the large hermaphroditic duct (LHD) and the foot. RIA of fractions from high-pressure liquid chromatography (HPLC) indicated that Pep itself was the predominant immunoreactive species in each of these tissues. Lower concentrations of Pep were found in a number of other peripheral tissues. Incorporation of labelled amino acid indicated that Pep was synthesized in the LHD, whereas Pep in the foot was synthesized primarily in central neurons and transported to the foot. IR-Pep was further localized by immunocytology. All peripheral IR-Pep appeared to be associated with neuronal fibers, most commonly varicose axons. Immunoreactive innervation of the LHD and foot was particularly dense but positive staining was also observed in other tissues including tegument, gill, gut, and heart. IR-Pep innervation in all tissues including the LHD appeared to be localized predominantly in muscular portions of the tissue. Spontaneous contractions of isolated LHD were accelerated by the application of Pep. Pep appears to act as a transmitter or neuromodulator at a number of different sites in Aplysia.     

Involvement of pedal peptide in locomotion in Aplysia: modulation of foot muscle contractions

Pedal peptide (Pep) is a 15-amino-acid neuropeptide that is localized within the Aplysia central nervous system (CNS) predominantly to a broad band of neurons in each pedal ganglion. Pep-neurons were identified by intracellular staining and immunocytology or by radioimmunoassay (RIA) of extracts from identified neurons. RIA reveals that 97% of all Pep-like immunoreactivity (IR-Pep) in pedal nerves is found in the three nerves that innervate the foot. Nearly every Pep-neuron sends an axon out at least one of these three nerves. Application of Pep to foot muscle causes an increase in the amplitude and relaxation rate of contractions driven by nerve stimulation or intracellular stimulation of pedal motor neurons. The increase in relaxation rate was the predominant effect. Intracellular recording in "split-foot" preparations reveals that Pep-neurons increase their overall firing rates and fire in bursts with each step during locomotion. Recovery of IR-Pep from foot perfusate following pedal nerve stimulation increases in a frequency-dependent fashion. Thus it appears that one function of Pep-neurons is to modulate foot muscle contractility during locomotion in Aplysia.     

Release of pedal peptide from Aplysia neurons in primary culture

Pedal peptide (Pep) is a modulatory neuropeptide that is predominantly synthesized in a group of neurons on the dorsal surfaces of the pedal ganglia of Aplysia. Following the determination that Pep is the major peptide selectively present in these neurons in situ, primary cell culture of single Pep-neurons was used to study the release of this neuropeptide. Individual Pep-neurons were grown in culture where they extended many branched neurites with large varicosities. Immunocytology revealed that these newly grown varicosities were intensely Pep immunoreactive. Cultured Pep-neurons, grown in a medium containing radiolabeled methionine, synthesized labeled Pep and transported it into their regenerated neurites. Finally, these neurons released radiolabeled Pep in a calcium- and stimulation-dependent fashion. These results, taken together with previous findings, strongly support the proposition that Pep is a transmitter in Aplysia.     

Differential Effects of Chemical Sympathectomy on Expression and Activity of Tyrosine Hydroxylase and Levels of Catecholamines and DOPA in Peripheral Tissues of Rats

Tyrosine hydroxylase (TH) mRNA and activity and concentrations of 3,4-dihydroxyphenylalanine (DOPA) and catecholamines were examined as markers of sympathetic innervation and catecholamine synthesis in peripheral tissues of sympathectomized and intact rats. Chemical sympathectomy with 6-hydroxydopamine (6-OHDA) markedly decreased norepinephrine and to a generally lesser extent TH activities and dopamine in most peripheral tissues (stomach, lung, testis, duodenum, pancreas, salivary gland, spleen, heart, kidney, thymus). Superior cervical ganglia, adrenals and descending aorta were unaffected and vas deferens showed a large 92% decrease in norepinephrine, but only a small 38% decrease in TH activity after 6-OHDA. Presence of chromaffin cells or neuronal cell bodies in these latter tissues, indicated by consistent expression of TH mRNA, explained the relative resistance of these tissues to 6-OHDA. Stomach also showed consistent expression of TH mRNA before, but not after 6-OHDA, suggesting that catecholamine synthesizing cells in gastric tissue are sensitive to the toxic effects of 6-OHDA. Tissue concentrations of DOPA were mainly unaffected by 6-OHDA, indicating that much of the DOPA in peripheral tissues is synthesized independently of local TH or sympathetic innervation. The differential effects of chemical sympathectomy on tissue catecholamines, DOPA, TH mRNA and TH activity demonstrate that these variables are not simple markers of sympathetic innervation or catecholamine synthesis. Other factors, including presence of neuronal cell bodies, parenchymal chromaffin cells, non-neuronal sites of catecholamine synthesis and alternative sources of tissue DOPA, must also be considered when tissue catecholamines, DOPA and TH are examined as markers of sympathetic innervation and local catecholamine synthesis.     

Serotonergic innervation of the foot of the pond snail Lymnaea stagnalis (L.)

The aminergic innervation of the foot of Lymnaea stagnalis was investigated using electron microscopy, immunocytochemistry, and HPLC. The foot was found to contain large amounts of serotonin and dopamine, though at lower concentrations than are found in nervous tissue. Serotonin containing tissue was concentrated in the ventral surface of the foot, under ciliated areas of the epidermis where it occurred in varicosities, with fine tracts joining these varicosities. Varicosities also occurred in deeper tissues, probably adjacent to mucus cells. Positive fluorescence for serotonin in axons was found in nerves innervating the foot, but few neuronal cell bodies containing serotonin were detected, indicating that most of the innervation was coming from the central ganglia. Axon varicosities were found using TEM on ciliated cells, mucus cells, and muscle cells as well as interaxonal junctions (possibly non-synaptic) within nerves. The neuronal varicosities contacting the ciliated cells and mucus cells contained mostly dense-cored vesicles of between 60 and 100 nm in diameter. Smaller, lucent vesicles also occurred in these terminals. The origin and significance of this innervation is discussed. It is suggested that both serotonin and dopamine may play a large role in controlling ciliary gliding by the foot.     

Tissue distribution of pneumadin immunoreactivity in the rat

Pneumadin (PNM) is a decapeptide, originally isolated from mammalian lungs, which exerts a potent stimulating effect on arginine-vasopressin (AVP) release, thereby evoking an antidiuretic effect. We have established a specific radioimmunoassay (RIA) method for rat PNM determination, the sensitivity of which is sufficient for measuring tissue content of the peptide. Moreover, raised antibodies have been used for the immunocytochemical detection of PNM in several rat organs. As expected, high concentrations of PNM were detected by RIA in newborn and adult rat lungs and immunocytochemistry (ICC) localized PNM immunoreactivity (IR) in the bronchial and bronchiolar epithelium. Very high concentrations of PNM were measured by RIA in the prostate, and ICC showed that PNM-IR is contained in the epithelial cells. RIA and ICC demonstrated the presence of low amounts of PNM in the thymus. The highest content of radioimmunoassayable PNM was found in the kidneys and intestinal tract, but dilution test suggested the presence of some interfering substances in these tissues. Accordingly, ICC-detectable PNM-IR was absent in the kidneys and present only in the duodenal criptae and Brunner's glands of the intestinal tract. RIA did not measure sizeable PNM concentrations in the thyroid gland, but ICC showed PNM-IR in C-cells. RIA and ICC did not detected PNM in testes, seminal vesicles, ovaries, uterus, pancreas, liver, spleen, adrenal glands, and heart. Taken together, our findings suggest that PNM, in addition to its role as hypothalamo-pituitary AVP secretagogue, may be involved in the autocrine-paracrine functional regulation of other peripheral organs, like lungs and prostate and perhaps duodenum, thymus and thyroid gland.     

Ca(2+)-ATPase and Mg(2+)-ATPase in Aplysia glial and interstitial cells: an EM cytochemical study.

The localization of Ca(2+)- and Mg(2+)-ATPases was determined in Aplysia central and peripheral nervous system, using an electron microscopic cytochemical method. The enzyme activity appeared localized to the membrane of glial granules (gliagrana), particularly in the peripheral nervous system of the esophagus, and on the plasma membrane of central glial cells adjacent to neuronal cell bodies. No calcium- and/or magnesium-ATPase activity was detectable on the plasma membrane of glial cells surrounding nerve axons in the pleuro-visceral connectives. These findings are discussed along two main lines: (a) the calcium-ATPase of the gliagrana coincides with a high intragranular calcium and/or proton concentration; and (b) the presence of a calcium-ATPase activity at the glio-neuronal interface around the neuronal cell bodies coincides with the use of calcium ions as charge carriers of the action potential, and its absence at the level of the axon with the concurrent functional use of sodium ions.     

A vasotocin-like peptide in Aplysia kurodai ganglia: HPLC and RIA evidence for its identity with Lys-conopressin G.

The presence of a vasopressin (VP)- or vasotocin (VT)-like peptide in the central nervous system of the gastropod mollusc Aplysia has been indicated previously. In the case of Aplysia californica, HPLC and RIA evidence suggested the peptide was VT-like but not identical with the nonmammalian vertebrate peptide [Arg8]VT (AVT). In the present study, anterior ganglia extracts from the related species Aplysia kurodai were analyzed by HPLC followed by RIA. Further analysis of the major AVT-IR peak showed it to be indistinguishable, in three distinct solvent systems, from the sea snail venom peptide Lys-conopressin G, but to be different from the vertebrate peptides [Arg8]VP (AVP), [Lys8]VP (LVP), AVT, oxytocin (OT), mesotocin, isotocin, aspargtocin, glumitocin, and valitocin, from the sea snail venom peptide Arg-conopressin S, and from the peptides [Lys8]VT and [Gln8]OT. In addition, the carboxymethylated (CM) A. kurodai peptide had the same HPLC retention time as CM-Lys-conopressin G. The HPLC/RIA results suggest that (i) based on the properties of the solvent systems used, the A. kurodai peptide has two basic amino acids (like the conopressins but unlike the vertebrate peptides), and (ii) there is a high probability that the A. kurodai peptide is identical with Lys-conopressin G.     

Delta sleep-inducing peptide (DSIP)-like material exists in peripheral organs of rats in large dissociable forms

The presence of delta sleep-inducing peptide (DSIP) in brain has been shown by radioimmunoassay (RIA) and by immunocytochemistry. We now describe the occurrence of DSIP-like material in the peripheral organs of the rat as measured by RIA. Tissue from 12 areas was extracted with water, and the amounts of immunoreactive material found to be between 86 pg/mg tissue (muscle) and 849 pg/mg (stomach). Recoveries of about 80% of added DSIP were achieved at tissue concentrations of 1 mg/ml or less. This percentage was reduced in liver at higher concentrations. The percentage of small peptide adsorbed by charcoal was greatly increased at lower tissue concentrations in all organs. This effect was significant and linear. Chromatography on columns of Sephadex G-15 and G-25 showed immunoreactive material mostly larger than DSIP. Digestion with trypsin, however, produced small immunoreactive peptides with only a minimal reduction in total immunoreactivity. Thus, DSIP-like material is widespread in peripheral tissues and appears to exist mainly in a large form, probably bound to protein, that can be reduced in size by tryptic digestion and can be dissociated at lower concentrations of tissue to yield small immunoreactive peptides.     

Mytilus inhibitory peptides (MIP) in the central and peripheral nervous system of the pulmonate gastropods, Lymnaea stagnalis and Helix pomatia: distribution and physiological actions

The distribution and neuroanatomy of Mytilus inhibitory peptides (MIP)-containing neurons in the central nervous system and their innervation pattern in the peripheral nervous system of the pulmonate snail species, Lymnaea stagnalis and Helix pomatia, have been investigated immunocytochemically, by applying an antibody raised to GSPMFVamide. A significant number of immunoreactive neurons occurs in the central nervous system of both species (Lymnaea: ca 600-700, Helix: ca 400-500), but their distribution is different. In Lymnaea, labeled neurons are found in all central ganglia where a number of large and giant neurons, previously identified physiologically, reveal MIP immunoreactivity. In Helix, most of the immunolabeled neurons are small (12-30 microm) and concentrated in the buccal and cerebral ganglia; the parietal ganglia are free of labeled cells. In both species, the ganglionic neuropils, peripheral nerves, connectives, and commissures are richly supplied with immunolabeled fibers. The MIP-immunoreactive innervation pattern in the heart, intestine, buccal mass and radula, and foot is similar in both species, with labeled axonal bundles and terminal-like arborizations (buccal mass, foot) or a network of varicose fibers (heart, intestine). Intrinsic neurons are not present in these tissues. The application of GSPYFVamide inhibits the spontaneous contractions of the esophageal longitudinal musculature in Helix, indicating the bioactivity of the peptide. An outside-out patch-clamp technique has demonstrated that GSPYFVamide opens the K+ channels in central nerve cells of Helix. Injection of GSPYFVamide into the body cavity inhibits the feeding of starved Helix. A wide modulatory role of MIP at central and peripheral levels is suggested in Lymnaea and Helix, including the participation in intercellular signalling processes and remote neurohormonal-like control effects.     

Catecholamine neurons in Aplysia: improved light-microscopic resolution and ultrastructural study using paraformaldehyde and glutaraldehyde (FaGlu) cytochemistry

We have modified the formaldehyde-glutaraldehyde (FaGlu) histofluorescence method of Furness, Costa, and Blessing (1977a) and Furness, Costa, and Wilson (1977b) to examine wholemounts and sections of both juvenile and adult ganglia as well as peripheral tissues of Aplysia californica. FaGlu fluorescence is the result of a reaction between formaldehyde and tissue catecholamines to produce water-insoluble (fixed) fluorophores. In serially sectioned cerebral ganglia, 70-80 positive neurons were observed (many in clusters of 10-20 cells), many more than were found using the glyoxylic acid technique. Catecholamine-containing varicosities were densely packed in localized portions of the neuropil of all central ganglia. Exclusive localization in the neuropil of presumed dopamine release sites is similar to that previously found for the neuropeptide SCP but differs from the widespread ramification of varicose neurites containing 5-HT, FMRFamide, and ELH. The FaGlu technique also enabled us to study the ultrastructure of catecholamine-containing neurons. In contrast to the larger vesicles found in serotonergic and histaminergic neurons, these dopaminergic neurons contain 70 nm dense-cored vesicles.     

Metabolism of acetylcholine in the nervous system of Aplysia californica. I. Source of choline and its uptake by intact nervous tissue

Although acetylcholine is a major neurotransmitter in Aplysia, labeling studies with methionine and serine showed that little choline was synthesized by nervous tissue and indicated that the choline required for the synthesis of acetylcholine must be derived exogenously. Aanglia in the central nervous system (abdominal, cerebral, and pleuropedals) all took up about 0.5 nmol of choline per hour at 9 muM, the concentration of choline we found in hemolymph. This rate was more than two orders of magnitude greater than that of synthesis from the labeled precursors. Ganglia accumulated choline by a process which has two kinetic components, one with a Michaelis constant between 2-8 muM. The other component was not saturated at 420 muM. Presumably the process with the high affinity functions to supply choline for synthesis of transmitter, since the efficiency of conversion to acetylcholine was maximal in the range of external concentrations found in hemolymph.     

ProCNP and CNP are expressed primarily in male genital organs

Lack of knowledge about the cellular origin of C-type natriuretic peptides (CNP) in the body has hampered the understanding of their biology. We examined the tissue specific expression of proCNP and CNP in the pig. The concentration of the CNP precursor, proCNP, was measured in extracts of 32 different tissues using a newly developed RIA. In 22 tissue extracts, we also measured CNP using a commercial RIA. In selected tissues, CNP mRNA was quantified by PCR, and the cellular CNP and proCNP localization was visualized by immunocytochemistry. Extracts from selected tissues were examined by gel chromatography. The highest peptide concentrations were found in extracts from the epididymis, seminal vesicles and prostate. CNP mRNA in the seminal vesicles and epididymis was 125-fold higher than in the other tissues examined. Gel chromatography showed that a CNP-53-like peptide is the dominant CNP tissue-form. Immunocytochemistry confirmed the pattern of peptide expression measured by RIA. In conclusion most proCNP-derived peptides are synthesized in epithelial cells in the epididymis, the prostate gland and in the seminal vesicles. The expression in male genital organs suggests a role of CNP in reproduction.     

SCN efferents to peripheral tissues: implications for biological rhythms.

The suprachiasmatic nucleus (SCN) is the principal generator of circadian rhythms and is part of an entrainment system that synchronizes the animal with its environment. Here, we review the possible communication of timing information from the SCN to peripheral tissues involved in regulating fundamental physiological functions as revealed using a viral, transneuronal tract tracer, the pseudorabies virus (PRV). The sympathetic nervous system innervation of the pineal gland and the sympathetic outflow from brain to white adipose tissue were the first demonstrations of SCN-peripheral tissue connections. The inclusion of the SCN as part of these and other circuits was the result of lengthened postviral injection times compared with those used previously. Subsequently, the SCN has been found to be part of the sympathetic outflow from the brain to brown adipose tissue, thyroid gland, kidney, bladder, spleen, adrenal medulla, and perhaps the adrenal cortex. The SCN also is involved in the parasympathetic nervous system innervation of the thyroid, liver, pancreas, and submandibular gland. Individual SCN neurons appear connected to more than one autonomic circuit involving both sympathetic and parasympathetic innervation of a single tissue, or sympathetic innervation of two different peripheral tissues. Collectively, the results of these PRV studies require an expansion of the traditional roles of the SCN to include the autonomic innervation of peripheral tissues and perhaps the modulation of neuroendocrine systems traditionally thought to be controlled solely by hypothalamic stimulating/inhibiting factors.     

Expression of basic fibroblast growth factor in the nervous system of early avian embryos

Basic fibroblast growth factor (bFGF) promotes the survival of a subpopulation of non-neuronal cells developing from trunk neural crest. It was therefore important to determine whether this factor is present in the nervous system at early developmental stages. Immunocytochemistry using specific polyclonal and monoclonal antibodies was combined with three highly sensitive assays: bFGF-induced proliferation of bovine adrenal cortex-derived capillary endothelial cells (ACE), a radioimmunoassay for bFGF (RIA) and Western blot analysis. bFGF immunoreactivity was localized to the cytoplasm of neuroepithelial cells derived from embryonic day 2 (E2) quail neural tubes and cultured for one day in a chemically defined medium. Specific staining was observed in young sensory neurons in cultures of neural crest clusters as well as in a subpopulation of non-neuronal cells. In cultured E7 dorsal root ganglia, immunostaining was confined to neuronal cell bodies and fibers. In situ, staining of spinal cord and ganglionic neurons appeared on E6 and increased in intensity towards E10. Various mesoderm-derived structures such as the limb buds, the mesenchyme dorsal to the neural tube, the vertebral muscles and cartilage showed specific staining patterns in addition to neural tissue. In agreement with the results of immunocytochemical studies, 1.4ng bFGF per mg protein was detected in spinal cord extracts by RIA as early as E3, its concentration increased to 8.0 ng mg-1 on E5 and then to a maximum of 18.0 ng mg-1 protein on E10, this was followed by a subsequent decrease in concentration in older embryos. On the other hand, high levels of bFGF were present in vertebral tissues from E10 onwards. Extracts of immunopositive tissues were subjected to heparin-Sepharose affinity chromatography and eluted in a stepwise salt gradient. Fractions that eluted from the columns at 2 M NaCl contained a bFGF-like protein as revealed by their ability to stimulate the proliferation of ACE cells and by Western blot analysis. These data demonstrate that bFGF is expressed during early nervous system development in both central and peripheral neurons.     

Measurement of plasma and tissue relaxin concentrations in the pregnant hamster and fetus using a homologous radioimmunoassay

A homologous hamster relaxin RIA was developed to evaluate plasma and tissue concentrations of relaxin in the latter half of pregnancy in this species. Relaxin protein and mRNA were localized using antibodies developed to synthetic hamster relaxin and gene-specific molecular probes, respectively. Molecular weight and isoelectric point of the synthetic and native hormones were identical by electrophoretic methods, and synthetic hamster relaxin was active in the mouse interpubic ligament bioassay. Synthetic hormone was used as tracer and standard with rabbit antiserum to the synthetic hormone in the RIA. Relaxin was assayed in blood samples recovered from the retro-orbital plexus on Days 6, 8, 10, 12, 14, 15, and 16 of gestation and on Days 1 and 5 postpartum. Relaxin was first detected on Day 8 of gestation (3.7 +/- 0.6 ng/ml), increased to reach a maximum in the evening of Day 15 (826.0 +/- 124.0 ng/ml), and decreased by Day 16 (day of parturition). Relaxin concentrations were assayed in aqueous extracts of implantation sites (Days 6, 8, and 10) and chorioallantoic placentae (Days 12, 14, and 15). Concentrations were low on Day 6 (0.02 +/- 0.001 microg/g tissue), increased to Day 15 (6.96 +/- 0.86 microg/g tissue), and subsequently declined by the evening of Day 15. Relaxin protein and mRNA were localized to primary and secondary giant trophoblast cells in the chorioallantoic placental trophospongium. However, relaxin protein was not localized in ovaries of pregnant animals or oviductal tissues of cycling animals. Significant quantities of relaxin were detected in the serum of fetal hamsters recovered on Day 15.     

Characterization of phosphonoglycosphingolipids containing pyruvate: localization in Aplysia nerve bundles

A phosphonoglycosphingolipid, designated as FGL-IIb, was first identified in nerve fibers of Aplysia kurodai by two-dimensional TLC (Abe, S. et al. (1986) Biomed. Res. 7, 47-51), and its chemical structure has been determined to be 3,4-O-(1-carboxyethylidene)]Gal beta 1----3GalNac alpha 1----3(Fuc alpha 1----2)(2-aminoethylphosphonyl----6)Gal beta 1----4Glc beta 1----1ceramide (Araki, S. et al., submitted). Cryostat and paraffin sections of the nervous tissue and skin of Aplysia were examined immunohistochemically with antiserum against FGL-IIb. With this antiserum, only nerve bundles were stained distinctly: nerve cells in ganglia and in subcutaneous and muscular tissues and other cell elements were not stained. From histochemical findings in cryostat sections pretreated with chloroform-methanol (2 : 1, v/v) and from the results of Western blot analysis of the nervous tissue, the staining was concluded to be due to glycolipid antigens. The antiserum reacted with FGL-IIb and other phosphonoglycosphingolipids named FGL-I, FGL-IIa, FGL-V, and F-9 on TLC plates. This reactivity of FGL-IIb was abolished by mild acid-methanol treatment, and the lost reactivity was recovered by alkaline hydrolysis. These findings suggest that the free carboxyl group of the pyruvic acid of FGL-IIb is essential for the immunological reaction and that all the glycolipids listed above have the same epitope as that of FGL-IIb. Immunohistochemical findings indicated that these glycolipids including FGL-IIb are localized specifically in nerve bundles of Aplysia.     

Distribution of the Aplysia cardioexcitatory peptide,NdWFamide, in the central and peripheral nervous systems of Aplysia

NdWFamide is an Aplysia cardioexcitatory tri-peptide containing D-tryptophan. To investigate the roles of this peptide, we examined the immunohistochemical distribution of NdWFamide-positive neurons in Aplysia tissues. All the ganglia of the central nervous system (CNS) contained NdWFamide-positive neurons. In particular, two left upper quadrant cells in the abdominal ganglion, and the anterior cells in the pleural ganglion showed extensive positive signals. NdWFamide-positive processes were observed in peripheral tissues, such as those of the cardio-vascular system, digestive tract, and sex-accessory organs, and in the connectives or neuropils in the CNS. NdWFamide-positive neurons were abundant in peripheral plexuses, such as the stomatogastric ring. To examine the NdWFamide contents of tissues, we fractionated peptidic extracts from the respective tissues by reversed-phase high-pressure liquid chromatography and then assayed the fractions by competitive enzyme-linked immunosorbent assay. A fraction corresponding to the retention time of synthetic NdWFamide contained the most immunoreactivity, indicating that the tissues contained NdWFamide. The prevalence of the NdWFamide content was roughly in the order: abdominal ganglion >heart >gill >blood vessels >digestive tract. In most of the tissues containing NdWFamide-positive nerves, NdWFamide modulated the motile activities of the tissues. Thus, NdWFamide seems to be a versatile neurotransmitter/modulator of Aplysia and probably regulates the physiological activities of this animal.     

NPY样免疫反应在蝾螈发育过程中神经系统的定位研究

By immuno-cytochemical method the localization of neuropeptide Y (NPY) in the nervous system during embryonic development of Cynops orientalis was studied. The results revealed that NPY was first localized in the peripheral nervous system (late tail-bud stage), and later appeared in the central nervous system (larval stage) where it appeared with the appearance of glial cells. Very probably with the migration of neural crest cells NPY appeared first in the peripheral nervous system and then distributed to the central nervous system.     

Distribution and molecular forms of brain natriuretic peptide in the central nervous system, heart and peripheral tissue of rat

The amino acid sequence of rat brain natriuretic peptide (rBNP) precursor has recently been deduced by the cDNA cloning method (1). In the present study, a radioimmunoassay (RIA) system for rBNP was newly established, and regional distribution of rBNP in the central nervous system, heart and other peripheral tissue of rat was investigated. In heart, especially in cardiac atrium, a high concentration of immunoreactive (ir-) rBNP was detected and identified as rBNP-45 and gamma-rBNP. No significant amount of ir-rBNP was found in other tissues examined including the central nervous system. Especially in brain, no ir-rBNP was detected, while ir-rat atrial natriuretic peptide (rANP) was observed at a relatively high concentration. These results demonstrate a sharp contrast between rat and porcine brains in ir-BNP distribution.