Immunochemical analysis and immunocytochemical localization of crustacean hyperglycemic hormone from the eyestalk of Macrobrachium rosenbergii

Heptapeptide (YANAVQV-NH2 = T-) and octapeptide (YANAVQTV-NH2 = T+), the putative C-terminus of crustacean hyperglycemic hormone (CHH) from the eyestalk of the giant freshwater prawn Macrobrachium rosenbergii, was synthesized by solid phase peptide synthesis and conjugated to bovine serum albumin, then used for immunization in swiss mice. Specificity of the antisera against both peptides was determined by indirect immunoperoxidase ELISA. The best response of antiserum against each peptide was used to determine the presence of the natural CHH in the eyestalk extract after separation by one step of RP-HPLC using dot-ELISA. The peptide immunoreactive substances were found in fraction 30 using anti-T- antiserum and in fraction 38 using anti-T+ antiserum. However, the CHH activity was found only in fractions 37-39. Immunocytochemical localization of peptide immunoreactive substances in the eyestalk of M. rosenbergii using the anti-T- antiserum did not show any specific staining. In contrast, the anti-T+ antiserum revealed specific staining on a group of 24 +/- 5 neurons in medulla terminalis ganglionic x-organ and their processes through the sinus gland. Similar results were also obtained using the eyestalk of another species, the giant tiger prawn Penaeus monodon, in which 34 +/- 4 neuronal cells were recognized. These results strongly indicate that the anti-T+ antibody can bind to the natural CHH while the anti-T- antibody can not; therefore, this isoform of CHH in M. rosenbergii should consist of 72 residues and threonine is predicted to be present at position 71.     

Immunocytochemical localization of pigment-dispersing hormone (PDH) and its coexistence with FMRFamide-immunoreactive material in the eyestalks of the decapod crustaceans Carcinus maenas and Orconectes limosus

Summary By use of a new antiserum, raised against synthetic pigment-dispersing hormone (PDH) from Uca pugilator, immunoreactive structures were studied at the light-microscopic level in the eyestalk ganglia of Carcinus maenas and Orconectes limosus. PDH-reactivity was mainly found in two types of neurons that were located between the medulla interna (MI) and the medulla terminalis (MT) in both species. Several additional perikarya were located in the distal part of the MI in O. limosus. In C. maenas, two to three PDH-positive perikarya were found in the region of the X-organ (XO) in the MT. Processes from single and clustered cells could be traced into all medullae of the eyestalk. Axons from the immunoreactive perikarya running between MI and MT form a larger tract that traverses the MT. Fibers from this tract give rise to extensive arborizations and plexuses throughout the proximal MT. A plexus containing very fine fibers is located at the surface of the MT in a position distal to the XO-area of C. maenas only. The proximal plexus also receives PDH-positive fibers through the optic nerve. PDH-perikarya in the cerebral ganglion may also project into the more distal regions of the eyestalk. Distal projections of the perikarya between the MI and MT consist of several branches. Most of these are directed toward the MI and ME (medulla externa) wherein they form highly organized, layered plexuses. One branch was traced into the principal neurohemal organ, the sinus gland (SG). In the SG, the tract gives off arborizations and neurosecretory terminals. It then proceeds in a proximal direction out of the SG, adjacent to the MT. Its further course could not be elucidated. The lamina ganglionaris (LG) receives PDH-fibers from the ME and fine processes from small perikarya located in close association with the LG in the distal part of the first optic chiasma. The architecture of PDH-positive elements was similar in both C. maenas and O. limosus. The distribution of these structures suggests that PDH is not only a neurohormone but may, in addition, have a role as a neurotransmitter or modulator. Immunostaining of successive sections with an FMRF-amide antiserum revealed co-localization of FMRFamideand PDH-immunoreactivities in most, but not all PDH-containing perikarya and fibers. The axonal branch leading to the SG and the SG proper were devoid of FMRFamide immunoreactivity.     

Immunolocalization of allatostatin-like neuropeptides and their putative receptor in eyestalks of the tiger prawn, Penaeus monodon

Allatostatin (AST)-like immunoreactivity (IR) was localized in the eyestalk of Penaeus monodon by immunohistochemistry using four anti-AST antibodies. Depending on the antisera, AST-like immunoreactivity was detected in neuronal bodies of the lamina ganglionalis, cell bodies anterior to the medulla externa and cell bodies on the anterior and posterior of the medulla terminalis. Neuronal processes in neuropiles of the medulla externa, medulla terminalis, sinus gland and nerve fibers in the optic nerve were also recognized. No IR in cell bodies or in nerve fibers was found in the medulla interna. Strong AST-like immunoreactivity was found in hundreds of cells of the X organ. The localization of AST-like peptides suggests that they function as neurotransmitters and/or neuromodulators. Antiserum to the Drosophila AST receptor (Dar-2) recognized a single protein in P. monodon eyestalk protein extracts that was identical in size to that found in Drosophila protein extracts. Using this antiserum the putative P. monodon AST receptor was localized to the sinus gland in both juvenile and adult eyestalks. To our knowledge this is the first demonstration of a neuropeptide receptor localized to the crustacean sinus gland. This suggests that ASTs may function directly on the sinus gland as a neuromodulator. In juvenile eyestalks, the putative AST receptor was also localized to neuronal X organ cells of the medulla terminalis in males but not in females. The significance of this sex-specific receptor localization is unclear but emphasizes that ASTs function within the nervous system of the eyestalk.     

Immunocytochemical localization of a substance in the eyestalk of the prawn,Palaemon serratus,reactive with an anti-FMRF-amide rabbit serum

Summary By use of a specific antiserum against the molluscan cardio-excitatory tetrapeptide FMRF-amide in combination with the PAP-method it was possible to obtain positive immunocytochemical reactions in several neurosecretory regions of the eyestalk of the prawn Palaemon serratus. FMRF-amide-like material was found in perikarya and nerve fibers of the medulla terminalis and in neurons in the lamina ganglionaris. The immunoreactivity observed in the glandular tissue located at the basal insertion of the eyestalk muscles must be ascribed to a non-specific reaction. The identification of immunopositive nerve fibers, ending on a nerve bundle in the medulla terminalis, and the fact that immunoreactive material was absent in the neurohemal sinus gland seem to indicate a neurotransmitter/neuromodulator function.     

The endocrine pancreas of Triturus cristatus: an immunocytochemical study

The endocrine pancreas of Triturus cristatus carnifex was studied with the aid of immunocytochemical methods, showing cells immunoreactive to anti-insulin serum (B cells), a small population of cells immunoreactive to anti-glucagon serum only (A cells), rare cells positive to anti-PP serum only (PP or F cells), and a larger population of cells immunoreactive both to anti-glucagon and to anti-PP sera. B cells lied in the core of the islet, while the A/PP cells were located at the periphery, forming digitations extending into the exocrine parenchyma. D cells were present in small number in the islet while they were more numerous scattered in the exocrine parenchyma. A/PP cells as well as D cells showed one or two long cytoplasmic extensions often in contact with blood vessels.     

A comparative immunocytochemical investigation of the crustacean hyperglycemic hormone (CHH) in the eyestalks of some decapod crustacea

The eyestalk of the astacideans Orconects limosus, Nephrops norvegicus, and Homarus gammarus, and the palinuran Palinurus vulgaris, was examined with an antiserum raised against purified crustacean hyperglycemic hormone (CHH) of the astacidean species Astacus leptodactylus. A distinct immunopositive reaction occurs in a group of neurosecretory cells in the medulla terminalis ganglionic X-organ (MTGX), in the MTGX-sinus gland tractus, and in a considerable part of the sinus gland. The immunoreactive sites in the eyestalk of the investigated species correspond to the site of production, storage, and release of the CHH. Preliminary investigations with this antiserum also indicate that a positive immunoreaction can be obtained in the eyestalk of other decapod crustaceans, for example, of the brachyuran Macropipus puber and the caridean Palaemon serratus.     

Molt-inhibiting hormone immunoreactive neurons in the eyestalk neuroendocrine system of the blue crab, Callinectes sapidus

The production of ecdysteroid molting hormones by crustacean Y-organs is negatively regulated by a neuropeptide, molt-inhibiting hormone. It is generally agreed that molt-inhibiting hormone is produced and released by the eyestalk neuroendocrine system. In the present study, immunocytochemical methods were used to detect molt-inhibiting hormone immunoreactive neurons in eyestalk ganglia of the blue crab, Callinectes sapidus. The primary antiserum used was generated against molt-inhibiting hormone of the green shore crab, Carcinus maenas. A preliminary Western blot analysis indicated the antiserum binds molt-inhibiting hormone of Callinectes sapidus. Using confocal and conventional immunofluorescence microscopy, molt-inhibiting hormone immunoreactivity was visualized in whole mounts and thin sections of Callinectes sapidus eyestalk ganglia. Immunoreactivity was detected in 15-25 neurosecretory cell bodies in the medulla terminalis X-organ, their associated axons and collateral branches, and their axon terminals in the neurohemal sinus gland. The cellular organization of molt-inhibiting hormone immunoreactive neurons in blue crabs is generally similar to that reported for other crab species. The combined results suggest the cellular structure of the molt-inhibiting hormone neuroendocrine system is highly conserved among brachyurans.     

Differential expression of CMG peptide and crustacean hyperglycemic hormones (CHHs) in the eyestalk of the giant tiger prawn Penaeus monodon

Mouse antiserum against C-terminal amide of Pem-CMG (a peptide in the family of CHH/MIH/GIH) penta-deca peptide (RPRQRNQYRAALQRLamide=CMG-15) was generated and used for localization of the peptide in tissue and extract of the eyestalk of Penaeus monodon by means of immunohistochemistry and dot-ELISA in comparison with anti-T+ antiserum (T+=YANAVQTVamide : the putative C-terminal amide of crustacean hyperglycemic hormone (CHH) of Macrobrachium rosenbergii). The anti-CMG-15 antiserum did not show cross-reactivity to T+ peptide by dot-ELISA and vice versa for anti-T+ antiserum. In dot-ELISA of eyestalk extract of P. monodon after one step separation by RP-HPLC, anti-CMG-15 antiserum recognized different peptide fractions (F38-39) from those recognized by anti-T+ antiserum (F19, 40-41 and 47-51). Most of the T+ immunoreactive fractions (except F19) show higher hyperglycemic activity than the CMG immunoreactive fractions. In immunohistochemical localization, anti-CMG antiserum recognized only 2-3 neurons in medulla terminalis X-organ complex (MTXO) with long processes terminated in the sinus gland. The CMG-immunoreactive neurons were clearly distinct from CHH containing neurons situated in the same area. This evidence confirms the existing of CMG peptide which may play distinct roles from CHHs in hormonal regulation in P. monodon.     

Cloning and expression of a cDNA encoding human placental protein 11, a putative serine protease with diagnostic significance as a tumor marker

The placental protein 11 (PP11) can act as a tumor marker because of its specific association with various forms of cancer. A lambda gt11 cDNA library prepared from human placenta was screened with a polyclonal anti-PP11 antiserum. Out of 10(6) independent clones, only one clone reacted with the anti-PP11 antiserum. The isolated cDNA coded only for the carboxy-terminal part of PP11 and was subsequently used to rescreen a lambda gt10 placental cDNA library. Two cDNA clones out of 10(6) screened were identified encoding the entire protein of 369 amino acids, including a typical hydrophobic signal sequence of 18 amino acids. Expression of the PP11 cDNA coding sequence in Escherichia coli resulted in the synthesis of a protein with the expected size which can be specifically immunoprecipitated with anti-PP11 antiserum. Fractionation experiments revealed that two forms of the protein are present in the bacterial cell: a higher-molecular-weight form of approximately 42 kD in the cytoplasm and a smaller-molecular-weight form of approximately 42 kD in the periplasm. This result indicates that PP11 can be synthesized in E. coli and is process by removal of the hydrophobic signal sequence. Both the placental and the processed recombinant PP11 protein exhibit a protease activity.     

Seven novel FMRFamide-like neuropeptide sequences from the eyestalk of the giant tiger prawn Penaeus monodon

FMRFamide-like immunoreactivity (FLI) was localized in the eyestalk of Penaeus monodon by immunohistochemistry using a combination of three anti-FMRFamide-like peptide (FLPs) monoclonal antibodies. Approximately 3000 small neuronal cell bodies in the lamina ganglionalis; 100 medium to large size at the ganglion between the medulla interna and the medulla terminalis; and 250 medium size around the medulla terminalis were stained intensely. The neuronal processes in neuropils of the medulla externa, medulla interna, medulla terminalis, sinus gland and some nerve fibers in the optic nerve were also recognized. The small cell bodies, approximately 1500 cells, anterior to the medulla externa were stained inconsistently and the neuronal processes were not observed from these cells. Isolation of FLPs from 9000 eyestalks was performed using methanol/acetic/water (90:1:9) extraction. After the extract was partially purified using C18 cartridges, it was further purified by five to seven steps of RP-HPLC using three kinds of columns: C18; C8; and cyano, and three solvent systems: acetonitrile/trifluoro acetic acid; aceonitrile/heptafluoro butyric acid; and acetonitrile/triethyl ammonium acetate. Dot-ELISA using the combination of the same antibodies was used to monitor FLPs in the fractions during purification processes. Seven new sequences of FLPs were identified which can be divided into four subgroups according to the primary structure of the C-terminus: (1) GDRNFLRFamide; (2) AYSNLNYLRFamide; (3) AQPSMRLRFamide, SQPSMRLRFamide, SMPSLRLRFamide and DGRTPALRLRFamide; and (4) GYRKPPFNGSIFamide. These data indicate the high complexity of this peptide family in which multiple forms are usually exist.     

Peptide tyrosine phenylalanine: a novel neuropeptide F-related nonapeptide from the brain of the squid, Loligo vulgaris.

A novel nonapeptide, sequence YAIVARPRFamide, was isolated from brain extracts of the squid, L. vulgaris. Designated peptide tyrosine phenylalanine (PYF), the peptide shows marked homology with the C-terminal nonapeptides of pancreatic polypeptide and neuropeptide F (NPF) from a number of sources. If PYF is the C-terminal nonapeptide of squid NPF, then it may be derived by a novel processing mechanism involving specific cleavage between two TYR residues. PYF may be a highly truncated, receptor-active variant of NPF.     

Biochemical characterization of enkephalin-like immunoreactive peptides of adrenal glands

The total enkephalin-like immunoreactive peptide content of adrenal glands from dog, cattle, guinea pig and rat was investigated by radioimmunoassay using a (met⁵)-enkephalin antiserum. Dog adrenals contain the highest amount of peptides, cattle and guinea pig adrenals contain lesser amounts, and the rat adrenals had the least amount (0.05% that of the dog). Comparison of the (met⁵)-enkephalin content of the adrenal cortex and medulla with that of whole bovine adrenal gland indicates that the peptides are concentrated in the medulla. Analysis of the chromaffin granules from bovine adrenal medulla indicates this to be the primary storage site for (met⁵)-enkephalin-like peptides. Gel chromatography reveals a molecular heterogeneity of the immunoreactive peptides in all species tested; high molecular weight peptides account for a larger proportion of the immunoreactivity when compared with the low molecular weight peptides.     

Three more novel FMRFamide-like neuropeptide sequences from the eyestalk of the giant freshwater prawn Macrobrachium rosenbergii

In addition to five FMRFamide-like peptides (FLPs) previously isolated from the eyestalk of the giant freshwater prawn Macrobrachium rosenbergii (16), three more new FLPs (Mar-FLP6-8) were identified from minor immunoreactive fractions of 5,000 eyestalk extracted in methanol/acetic acid/water: DGGRNFLRFamide, GYGDRNFLRFamide and VSHNNFLRFamide. These three peptides share 5-6 common residues at the C-terminus with Mar-FLP1,2 and 3. This evidence reveals that the structural diversity and complexity of the FLP family in M. rosenbergii are similar to that found in other invertebrate species.     

Specific inhibition of mouse oocyte nuclear protein phosphatase-1 stimulates germinal vesicle breakdown

Okadaic acid (OA)-induced germinal vesicle breakdown (GVBD) and localization of protein phosphatase-1 (PP1) in oocyte nuclei are suggestive of PP1's role in regulating oocyte GVBD. To explore this possibility, we microinjected protein phosphatase (PP) inhibitors OA, anti-PP1 antibody (anti-PP1), PP1 inhibitor I2, and anti-PP2A antibody (anti-PP2A) into nuclei of roscovitine (ROSC)-arrested mouse oocytes. Oocytes were also injected with recombinant PP1 in the absence of ROSC. Oocytes were assessed for GVBD and metaphase II (MII) development at 2 and 18 hr post-injection. Data were analyzed using Cochran-Mantel-Haenszel Statistics adjusted for time. Microinjection of OA significantly enhanced GVBD in comparison to controls at 2 and 18 hr (P < 0.01), yet had no effect on MII development. Similarly, microinjection of anti-PP1 resulted in significantly higher levels of GVBD compared to controls at 2 and 18 hr (P < 0.01). Interestingly, anti-PP1 microinjection also tended to enhance MII development at 18 hr in comparison to controls (P < 0.09). Microinjection of I2, anti-PP2A, and PP1 had no effect on GVBD or MII development. If reduction of PP1 activity was important for GVBD, one would anticipate an endogenous means of regulating PP1 activity at this developmental stage. In somatic cells, phosphorylation of PP1 at Thr320 causes PP1 inactivation. Germinal vesicle-intact oocytes did not contain phosphorylated PP1, as determined using a specific Thr320-Phospho-PP1 antibody, Western blot analysis, and confocal immunocytochemistry. At or around the time of GVBD, oocyte PP1 became phosphorylated at Thr320, which remained phosphorylated through MII development. These data indicate that inhibition of intra-nuclear PP1, through specific antibody neutralization, mimics OA-stimulated GVBD, providing the first direct evidence that nuclear PP1 is involved in regulation of oocyte nuclear membrane integrity. In addition, phosphorylation of PP1 occurs at/or around GVBD indicating that inactivation of PP1 is an important intracellular event in regulation of nuclear envelope dissolution at GVBD.     

Development of pigment-dispersing hormone-immunoreactive neurons in the American lobster: homology to the insect circadian pacemaker system?

We have examined the development of pigment-dispersing hormone (PDH)-immunoreactive neurons in embryos of the American lobster Homarus americanus Milne Edwards, 1837 (Decapoda, Reptantia, Homarida) by using an antiserum against β-PDH. This peptide is detectable in the terminal medulla of the eyestalks and the protocerebrum where PDH immunoreactivity is present as early as 20% of embryonic development. During ontogenesis, an elaborate system of PDH-immunoreactive neurons and fibres develops in the eyestalks and the protocerebrum, whereas less labelling is present in the deuto- and tritocerebrum and the ventral nerve cord. The sinus gland is innervated by PDH neurites at hatching. This pattern of PDH immunoreactivity has been compared with that found in various insect species. Neurons immunoreactive to pigment-dispersing factor in the medulla have been shown to be a central component of the system that generates the circadian rhythm in insects. Our results indicate that, in view of the position of the neuronal somata and projection patterns of their neurites, the immunolabelled medulla neurons in insects have homologous counterparts in the crustacean eyestalk. Since locomotory and other activities in crustaceans follow distinct circadian rhythms comparable with those observed in insects, we suggest that PDH-immunoreactive medulla neurons in crustaceans are involved in the generation of these rhythms. This study was supported by Deutsche Forschungsgemeinschaft (DFG) grant Ha 2540 and National Science Foundation grant IBN 0344448. S.H. was a Heisenberg Fellow of the DFG during the experimental part of this study. Bill Hansson and the Max Planck Society provided support during the final period of work reported in this paper.     

Immunohistochemical evidence of gastro-entero-pancreatic neurohormonal peptides of vertebrate type in the nervous system of the larva of a dipteran insect, the hoverfly, Eristalis aeneus

Using rabbit and guinea-pig antisera, raised against GEP neurohormonal peptides of mammalian origin, cells were observed in the brain and/or in the fused ventral ganglia of the last (fifth) larval instar of the hoverfly, Eristalis aeneus, being immunoreactive with antisera against insulin, somatostatin, glucagon, PP, secretin, gastrin/CCK/caerulein; substance P, enkephalin and endorphin. Most of these GEP neurohormonal peptides also occurred in nerve fibers. No immunoreactive cells or nerve fibers could be detected with antisera against GIP, VIP, (the central fragments of) CCK, bombesin or neurotensin. The antisera tested failed to reveal any immunoreactive cells or nerves in Weismann's ring (fused corpus allatum/corpus cardiacum and thoracic gland) or in different parts of the alimentary tract. The observations support the hypothesis that neuronal GEP hormonal peptide production in the brain is a genuinely original mechanism and the appearance of endocrine cells in the gut a later feature in evolution.     

Radioimmunologic and radioreceptor studies of the pharmacokinetics of the enkephalin analog dalargin in man

Pharmacokinetics of dalargin, an opioid hexapeptide, was investigated on 7 males by two approaches. Dalargin radioimmunoassay was performed using a highly specific antiserum reacting only with the whole molecule. In radioreceptor assay lyophilized rat brain membranes containing opiate receptors were used. 2-6 min after intravenous introduction of 1-10 mg dalargin, immunoreactive dalargin blood concentration was lower than 0.5 ng/ml. The results of radioreceptor assay were presented as a biexponential curve with a fast main phase of activity changes (90%, characteristic time 1.5-5.0 min) and a slow "clearance" phase (10% of the substance, characteristic time 85-200 min). Prolonged presence of receptor-active substances in the blood can be attributed to the products of dalargin degeneration, namely its N-terminal penta- and tetrapeptides.     

Pancreatic polypeptide-like material in nerves and endocrine cells of the rat

A region-specific antiserum (AbS11) raised against the carboxyl-terminal hexapeptide of pancreatic polypeptide has been employed to measure rat pancreatic polypeptide specifically and to demonstrate apparent immunoreactivity in nerves and in endocrine cells outside the pancreas. The concentration of pancreatic polypeptide in the head of the rat pancreas measured with AbS11 (176 +/- 47 pmol/g) was 750 fold higher than that measured with a conventional anti-bPP antiserum (0.23 +/- 0.08 pmol/g). Column chromatographs of rat pancreatic extracts demonstrated two peaks of immunoreactivity both eluting after the porcine pancreatic polypeptide standard. AbS11 also detected specific immunoreactivity in rat brain (470 fmol/g) which went undetected in convention assays. Although immunohistochemical studies with AbS11 and human pancreatic polypeptide antiserum demonstrated immunoreactivity in the same population of pancreatic endocrine cells, immunoreactive nerve fibres and enteroglucagon cells were only demonstrable with AbS11. These studies demonstrate that the carboxyl terminus of rat pancreatic polypeptide is immunochemically similar to that of higher mammals. Furthermore, neural and extrapancreatic endocrine variants of this peptide share an immunochemical determinant contained within the carboxyl-terminal hexapeptide.     

The complete primary structure of pancreatic polypeptide from the European common frog, Rana temporaria

Using an antiserum directed against the highly-conserved C-terminal hexapeptide amide of mammalian pancreatic polypeptide (PP), numerous immunoreactive endocrine cells were identified within the pancreas of the European common frog, R. temporaria. An acidified ethanolic extract of pancreatic tissue (0.859 g, n = 35) contained 26.2 nmol equivalents/g of tissue. Gel permeation chromatography of the extract resolved a single peak of immunoreactivity co-eluting with synthetic bovine PP standard. Reverse phase HPLC of this material resolved a single peak of immunoreactivity which was purified to homogeneity following chromatography on a semipreparative C-18 column and an analytical C-8 column. Plasma desorption mass spectrometry (PDMS) of the purified peptide resolved a single component with a molecular mass of 4240.9 Da. Direct gas phase sequencing established the sequence of the first 26 residues. Following incubation of the peptide with endopeptidase Asp-N and direct application of the digest to the sequencer, the entire primary structure of the peptide was established as: APSEPHHPGDQATQDQLAQYYSDLYQYITFVTRPRF. The derived molecular mass of this peptide, incorporating a C-terminal amide, was 4240.6 Da which is entirely consistent with that obtained by PDMS.     

白斑迷蛱蝶视觉系统中GABA和5-HT能神经元的分布

采用树脂石蜡(Colophony-Paraffin,CP)组织包埋切片技术和链霉菌抗生物素蛋白一过氧化物酶(Streptavidin—peroxidase,SP)免疫组织化学方法,首次报道了GABA和5-HT两种神经递质在白斑迷蛱蝶视觉系统(复眼及视叶)中的分布。与以往所报道的昆虫不同,白斑迷蛱蝶复眼中部分光感细胞对GABA和5-HT抗血清产生免疫反应。每侧视叶中约有2600多个GABA能阳性神经元,它们共分为6群。其中3群位于外髓附近(M1-3),另外三群位于内髓复合体边缘(LC1-3)。GABA能神经元发出的轴突在整个视叶的3个神经纤维网中都有分布。相比之下,视叶对5-HT抗血清的反应较弱,视叶神经纤维网中不存在代表5-HT阳性反应的粗大静脉曲张状纤维,只有一些排列规则的细小纤维。每侧视叶只有位于外髓附近的25个神经元呈现阳性反应,它们的分布位置与部分M3群的GABA能样神经元相同。本文还探讨了5-HT和GABA在调节视觉信息时可能发挥的作用[动物学报50(5)：770—777,2004]。