Immunohistochemical demonstration of [D-Ala2]deltorphin-I in amacrine cells of rat retina

Expression and Localization of TRK-Fused Gene Products in the Rat Brain and Retina

The TRK-fused gene (TFG in human, Tfg in rat) was originally identified in human papillary thyroid cancer as a chimeric form of the NTRK1 gene. It has been reported that the gene product (TFG) plays a role in regulating phosphotyrosine-specific phosphatase-1 activity. However, no information regarding the localization of Tfg in rat tissues is available. In this study, we investigated the expression of Tfg mRNA in normal rat tissues using reverse transcription-polymerase chain reaction (RT-PCR). We also produced an antibody against Tfg gene products and examined the localization of TFG in the rat brain and retina. The RT-PCR experiments demonstrated that two types of Tfg mRNA were expressed in rat tissues: the conventional form of Tfg (cTfg) and a novel variant form, retinal Tfg (rTfg). RT-PCR analyses demonstrated that cTfg was ubiquitously expressed in rat tissues, while rTfg was predominantly expressed in the brain and retina. Western blot analysis demonstrated two bands with molecular weights of about 30 kDa and 50 kDa in the rat brain. Immunohistochemistry indicated that TFG proteins were predominantly expressed by neurons in the brain. In the rat retina, intense TFG-immunoreactivity was detected in the layer of rods and cones and the outer plexiform layer.

Immunohistochemical Mapping of TRK-Fused Gene Products in the Rat Brainstem

The TRK-fused gene (TFG in human, Tfg in rat) was originally identified in human papillary thyroid cancer as a chimeric form of the NTRK1 gene. It was since reported that the gene product (TFG) plays a role in regulating phosphotyrosine-specific phosphatase-1 activity. As shown in the accompanying paper, we produced an antibody to rat TFG and used it to localize TFG to selected neurons in specific regions. In the present study, we mapped the TFG-positive neurons in the brainstem, cerebellum, and spinal cord of rats. In the brainstem, neurons intensely positive for TFG were distributed in the raphe nuclei, the gigantocellular reticular nucleus, the reticulotegmental nucleus of the pons, and some cranial nerve nuclei such as the trigeminal nuclei, the vestibulocochlear nuclei, and the dorsal motor nucleus of the vagus. Purkinje cells in the cerebellum and motor neurons in the spinal anterior horn were also positive for TFG. These results provide fundamental data for studying the functions of TFG in the brain.

Immunoreactive neurons in the brain of two mouse strains after incubation with an antiserum recognizing Asp-Val-Val-Gly.NH2 (DVVG), the C-terminal fragment of (D-Ala2)-deltorphin I

D-Ala(2)-deltorphin I (DADTI) is a heptapeptide amide first extracted from frog skin that displays a high selectivity and affinity for delta opioid receptors. Previous studies using a polyclonal antiserum specific for its C-terminal tetrapeptide-amide (DVVG) have already described in rat and mouse brain the presence of immunoreactive neurons, most of them belonging to the mesencephalic dopaminergic neurons. C57BL/6J (C57) and DBA/2J (DBA) are two inbred strains of mice well known for showing marked genotype-dependent differences for phenotypes related to differential brain dopamine functioning. Brain specimens of both inbred mouse strains were frozen, cut and immunostained using the same antiserum. Some sections were also double immunostained with monoclonal anti-tyrosine hydroxylase (TH). DVVG-immunoreactive neurons were observed among both dopaminergic and non-dopaminergic neurons. DVVG- and TH-immunoreactive neurons were observed among the dopaminergic A8, A9 and A10 mesencephalic nuclei. They were on average 21.9% more numerous in DBA than in C57 mice. DVVG-immunoreactive nerve fibres could be seen in limbic, striatal, cortical and thalamic areas. The distribution patterns of DVVG-IR and TH-IR nerve fibres differed most conspicuously within the infralimbic, prelimbic and cingulate cortices, forming a dense network in DBA but rare in C57 mice. Non-dopaminergic DVVG-immunoreactive neurons did not differ significantly in the two strains. Our finding that the number and distribution pattern of this dopaminergic neuronal subpopulation differed in the two mouse strains could provide morphological support for the known behavioural differences between the DBA and C57 strains under normal and experimental conditions.

Production and immunohistochemical application of antiserum against Tyr-D-Ala-Phe, a N-terminal tripeptide common to dermorphin/deltorphin family

Tyr-D-Ala-Phe is a N-terminal sequence commonly found in a peptide family including dermorphin and deltorphin. The tripeptide was synthesized and conjugated with poly L-lysine. Nuclear magnetic resonance (NMR) indicated that approximately 38 molecules of the tripeptide were bound to each molecule of poly L-lysine. The conjugate was used to immunize rabbits, and high titer antisera were obtained. An IgG fraction was purified by protein G affinity chromatography. A specific antibody to the tripeptide was then obtained by affinity chromatography using formylcellulofine conjugated with Tyr-D-Ala-Phe. On immunospot assay, the best IgG antibody was capable of detecting 125 ng of Tyr-D-Ala-Phe but failed to react even with 2.0 microg of Tyr-L-Ala-Phe or poly L-lysine. Our immunohistochemical examination selectively localized the secretory glands of frog skin.

Production of monoclonal antibody to deltorphin-I and its immunocytochemical application to adult rat brain and cultured rat brain neurons

A monoclonal anti-deltorphin-I antibody specifically recognizing its NH2-terminal region was produced. In the adult rat brain sections, it recognized immunoreactive nerve fibers mainly in the bed nucleus of stria terminalis, central nucleus of amygdala, lateral hypothalamus, hippocampus, substantia nigra, periaqueductal gray and locus ceruleus. Occasionally, positive somata were localized in the bed nucleus of stria terminalis, central nucleus of amygdala, supraoptic and periventricular nuclei. In primarily cultured neurons from various brain regions of new-born rats, the antibody immunostained strongly neuronal somata and processes. The abundant DADTI-immunoreactive substance in the cultured neurons promises to provide an alternative pathway to search for the counterpart of deltorphins in mammals.

Ontogeny of (D-Ala(2))-deltorphin I-like immunoreactive neurones in foetal rat brain

Foetal rat brain from embryonic day (ED) 12-22 was immunohistochemically studied to describe the time of first appearance and further distribution patterns of (D-Ala(2))-deltorphin-I-immunoreactive (DADTI-IR) nerve elements. The primary antiserum used in this study was a polyclonal antibody against DADTI previously used in adult and postnatal rat brain mapping. DADTI-IR nerve elements first appeared in the neuroepithelium of ventral mesencephalon on ED 13. From there, positive cell bodies migrated towards the mantle layer until they invaded the whole ventral mesencephalic tegmentum. They then reached their definitive position, corresponding to a subpopulation of the A8, A9 and A10 dopaminergic neurones that had been constantly observed also in the adult age. From ED 15-17, DADTI-positive nerve fibres appeared in the medial forebrain bundle, the neostriatum anlage, the accumbens nucleus, the olfactory tubercle, the fasciculus retroflexus, and the prefrontal cortex. All these locations have also been found in adult rats. From ED 14 onwards, transient DADTI-IR somata and nerve fibres were observed in retinal neuroepithelium, optic pathways as far as the superior colliculus, CA3 hippocampal field, reticular formation in the medulla oblongata. All these locations gradually disappeared either before birth (medulla oblongata) or within the first 3 weeks after birth. These results suggest that the DADT-like molecule recognised by our antibody has during the embryonic development a regulatory function in neuronal growth and differentiation.

The rat dermorphin-like immunoreactivity is supported by an aminopeptidase resistant peptide

Site-directed antibodies against synthetic related dermorphin peptides were previously produced and characterized. One of them, which specifically recognizes the crucial 'opioid message' (the N-terminal part of the dermorphin molecule (i.e. Tyr-D-Ala-Phe-Gly) was selected in order to detect and locate endogenous dermorphin-like molecules in rat, mouse and guinea pig tissues. Dermorphin-like peptides were found to be present in tissues known to contain peptides such as neurons in the central nervous system, nerve fibers in the gut and B and T immune cells. With all the tissues assayed, the HPLC profile obtained on the immunoreactive material showed the same main peak eluted at a retention time of 32 +/- 1 min. The results of biochemical experiments in which enzymatic treatments were performed on the dermorphin-like immunoreactivity indicate the immunoreactivity is a peptide resistant to aminopeptidase hydrolysis. This finding suggests the presence of a residue conferring resistance to proteolytic processes of this kind, which is likely to be a D-amino acid residue.

Ontogeny of preproenkephalin mRNA expression in the rat retina

Endogenous opioid systems (i.e. opioid peptides and opioid receptors) modulate developmental events in the neonatal mammalian retina. In the present study, the mRNA encoding preproenkephalin A (PPE), the prohormone for the opioid growth factor (OGF), [Met5]-enkephalin, was studied in the developing and the adult retinas of rats. Northern analysis indicated the presence of a 1.4-kb message in the developing and adult retinas corresponding to rat PPE mRNA. Quantitation showed that PPE message was present on postnatal day 1 at 5% of the adult level, and increased during development until the adult quantity was reached by postnatal day 27. In situ hybridization experiments first detected the presence of PPE mRNA in retinal tissues during late gestation. In late prenatal and neonatal retinas, PPE message was associated with areas of the developing retina containing proliferating neuroblasts and postmitotic cells. Later in development, message appeared to be located primarily within the inner retina, with abundant PPE mRNA associated with putative horizontal cells of the inner nuclear layer (INL). The adult retina showed a similar pattern of PPE gene expression in the cells of the INL. These findings document that the gene expression in the retina for PPE begins in the fetus, continues during retinal development, and coincides with the presence of a PPE mRNA derivative ([Met5]-enkephalin) that regulates DNA synthesis during retinal ontogeny. Our results are also the first to show the presence of PPE message in the adult mammalian retina, suggesting transcription of an opioid gene in the mature visual system.

Localization of [D-Ala2]deltorphin I-like immunoreactivity in perinatal rat respiratory system

The localization of [D-Ala2]deltorphin I, a delta-opioid receptor ligand, was studied in the lower respiratory tract of developing rats using an immunohistochemical method. [D-Ala2]-like immunoreactive cells were detected first in the principal bronchus as early as embryonic day 16. As embryos grew, positive cells became gradually visible everywhere from principal bronchi to respiratory bronchioles. The density of positive cells reached the highest level on embryonic day 21, but decreased gradually after birth. Positive cells were no longer seen on postnatal day 30 in any region of the airways. No positive cells were ever found in the trachea or alveoli of rats at any age studied. Ultrastructural examination indicated that the immunoreactive cells possessed a similar morphology to serous or Clara cells of the respiratory epithelium. Immunoreaction products tended to locate at the apical cytoplasm of positive cells. The results suggests that [D-Ala2]-like molecule(s) may be expressed transiently in serous cells or Clara cells, or both, of the rat bronchopulmonary tract. Such a molecule may act as a pulmonary growth-promoting or a differentiation-initiating factor in an early period of lung development.

Demonstration of [D-Ala2]deltorphin I-like immunoreactivity in mucosal epithelial cells of the rat gastrointestinal tract

Using a specific antiserum to [D-Ala2]deltorphin I (DADTI), a delta-opioid receptor ligand, the localization of positive structures was studied in rat gastrointestinal tract by immunocytochemistry. Immunoreactive staining was not detected in the stomach, colon, or neuronal elements of any gastrointestinal tissue. However, positive cells were distributed in the mucosal epithelium of the small intestine, including the duodenum, jejunum, and ileum. The density of positive cells was highest at a proximal part of the jejunum and was gradually decreased toward the duodenum or the distal end of the intestine. These positive cells had spindle-like somata that tended to locate more closely to the lumen compared with nonimmunoreactive cells. Some of the positive cells extended cytoplasmic basal processes toward the lamina propria. Immunoelectron microscopy revealed that positive reaction products occurred within the secretory granules as well as in the cytoplasm. Because these positive granules were frequently observed in the apical cytoplasm beneath the microvilli, it is suggested that the DADTI-like molecule(s) may be secreted to the lumen.