[Gastroesophageal reflux disease in patients receiving chemotherapy: clinical, endoscopic, morphological and immunohistochemical features]

THE PURPOSE OF THE STUDY

Determine the pathogenetic significance of express molecules PCNA, Bcl-2, NF-Kb and tachykinins (substance P, neurokinin A) in patients with gastroesophageal reflux disease (GERD), receiving polychemotherapy (PCT).

MATERIALS AND METHODS

In total 60 patients were examined with GERD time-divided into 2 equal groups on the receiving PCT Leukemia over standard dose for at least one year. The first group consisted of 30 subjects with non-erosive GERD (NEGERD) endoscopically positive form receiving PCT. The second group consisted of 30 subjects with erosive form of GERD (EFGERD) receiving PCT. Patients underwent endoscopy, morphological and immunohistochemical examination of the esophageal mucosa to the definition expression of molecules PCNA, Bcl-2, neurokinin A, substance P and factor Nf-Kb. In patients with refractory form of GERD to proton pump inhibitors therapy (PPIs), additionally imposed ursodeoxycholic acid.

THE RESULTS

Patients with NEGERD receiving PCT in 33.3% of cases formed refractory to PPIs form of the disease, when EFGERD refractoriness occurs in 46.7% of patients, which is associated with slowing the proliferation of epithelial cells of the esophagus due to decreased expression of PCNA. Reduced expression of neurokinin A in patients receiving PCT is associated with less activity and intensity of inflammation of esophageal mucosa. Against the background of a high degree of PCT expression of Bcl-2 and factor Nf-Kb, which may explain the frequent detection of atrophic and meta- plastic changes in the esophageal mucosa. Appointment of ursodeoxycholic acid in the complex therapy of GERD can overcome resistance to PPIs and improve the performance of cell renewal.

CONCLUSION

Due to the frequent development of GERD refractory to PPIs in patients suffering from diseases requiring the appointment of long-term courses of PCT requires the appointment of cytoprotective therapy, as that can be used ursodeoxycholic acid.

An indirect role for oncomir-519b in the expression of truncated neurokinin-1 in breast cancer cells

Neurokinin 1 (NK1) encodes full-length (NK1-FL) and truncated (NK1-Tr) receptors, with distinct 3' UTR. NK1-Tr exerts oncogenic functions and is increased in breast cancer (BC). Enhanced transcription of NK1 resulted in higher level of NK1-Tr. The 3' UTR of these two transcripts are distinct with NK1-Tr terminating at a premature stop codon. NK1-Tr mRNA gained an advantage over NK1-FL with regards to translation. This is due to the ability of miR519B to interact with sequences within the 3' UTR of NK1-FL, but not NK1-Tr since the corresponding region is omitted. MiR519b suppressed the translation of NK1-FL in T47D and MDA-MB-231 resulting in increased NK1-Tr protein. Cytokines can induce the transcription of NK1. However, our studies indicated that translation appeared to be independent of cytokine production by the BC cells (BCCs). This suggested that transcription and translation of NK1 might be independent. The findings were validated in vivo. MiR-519b suppressed the growth of MDA-MB-231 in 7/10 nude BALB/c. In total, increased NK1-Tr in BCCs is due to enhanced transcription and suppressed translation of NK1-FL by miR-519b to reduced tumor growth. In summary, we report on miRNA as a method to further regulate the expression of a spiced variant to promote oncogenesis. In addition, the findings have implications for therapy with NK1 antagonists. The oncogenic effect of NK1-Tr must be considered to improve the efficacy of current drugs to NK1.

Sputum neurokinin A in Egyptian asthmatic children and adolescents: relation to exacerbation severity

BACKGROUND

Neurogenic inflammation may participate in the development and progression of bronchial asthma. The molecular mechanisms underlying neurogenic inflammation are orchestrated by a large number of neuropeptides including tachykinins such as neurokinin A (NKA) and substance P. Tachykinins are secreted from sensory airway nerves and inflammatory cells after allergens exposure. In clinical practice, assessment of airway inflammation is difficult. Therefore, detection of biological markers of airway inflammation in sputum might offer help for proper monitoring of asthma severity.

AIM OF THE STUDY

We aimed to measure sputum NKA in relation to acute asthma exacerbations of varying severity.

METHODS

Sputum NKA was measured by enzyme-linked immunosorbent assay in 24 children and adolescents during and after acute asthma exacerbation and 24 healthy matched controls.

RESULTS

Sputum NKA was significantly higher in asthmatic patients during acute exacerbation than controls [217.5 (284) vs 10 (7) ng/ml, P < 0.001]. When patients with acute asthma exacerbation were followed-up till remission, sputum NKA levels decreased significantly, but they remained significantly higher than controls. Sputum NKA levels were significantly higher in severe than moderate and in moderate than mild exacerbations, and was negatively correlated to peak expiratory flow rate (r = -0.9, P < 0.001). Sputum NKA had significant positive correlations to eosinophil counts in blood and sputum (r = 0.6, P < 0.001 and r = 0.7, P < 0.001 respectively).

CONCLUSIONS

Sputum NKA is up-regulated during acute asthma exacerbation and it positively correlates to its severity. Thus, NKA may aid in objective classification of the exacerbation severity. In addition, NKA may be a target for new asthma therapy.

Stromal Derived Growth Factor-1α: Another Mediator in Neural-Emerging Immune System throughTac1Expression in Bone Marrow Stromal Cells

Stromal cell-derived growth factor-1alpha (SDF-1alpha) is a member of the CXC chemokines and interacts with the G protein, seven-transmembrane CXCR4 receptor. SDF-1alpha acts as a chemoattractant for immune and hemopoietic cells. The Tac1 gene encodes peptides belonging to the tachykinin family with substance P being the predominant member. Both SDF-1alpha and Tac1 peptides are relevant hemopoietic regulators. This study investigated the effects of SDF-1alpha on Tac1 expression in the major hemopoietic supporting cells, the bone marrow stroma, and addresses the consequence to hemopoiesis. Reporter gene assays with the 5' flanking region of Tac1 showed a bell-shaped effect of SDF-1alpha on luciferase activity with 20 ng/ml SDF-1alpha acting as stimulator, whereas 50 and 100 ng/ml SDF-1alpha acted as inhibitors. Gel shift assays and transfection with wild-type and mutant IkappaB indicate NF-kappaB as a mediator in the repressive effects at 50 and 100 ng/ml SDF-1alpha. Northern analyses and ELISA showed correlations among reporter gene activities, mRNA (beta-preprotachykinin I), and protein levels for substance P. Of relevance is the novel finding by long-term culture-initiating cell assays that showed an indirect effect of SDF-1alpha on hemopoiesis through substance P production. The results also showed neurokinin 1 and not neurokinin 2 as the relevant receptor. Another crucial finding is that substance P does not regulate the production of SDF-1alpha in stroma. The studies indicate that SDF-1alpha levels above baseline production in bone marrow stroma induce the production of substance P to stimulate hemopoiesis. Substance P, however, does not act as autocrine stimulator to induce the production of SDF-1alpha. This study adds SDF-1alpha as a mediator within the neural-immune-hemopoietic axis.

[A qualitative and quantitative analysis on the development of NKA-immunoreaction in duodenum of rats]

OBJECTIVE

To explore the expression and change of neurokinin A (NKA) in rat duodenum during development.

METHODS

PAP immunocytochemistry method and image analysis were used to detect systematically the expression of NKA in rat duodenum from day 13 of embryo to adult stage.

RESULTS

In rat duodenum, the NKA-IR was first found in the myenteric plexus at day 14 of embryo, and then was found in the longitudinal muscle layer, circular muscle layer, intestinal villus, mucosa plexus, intestinal gland, muscularis mucosae, submucosa, submucosal plexus and deep muscular plexus. At day 30 after birth, the distribution feature of adult rat was seen. The results of quantitative analysis were in accord with the developmental change of NKA-IR in duodenum. The NKA-IR positive cells showed the typical feature of morphology and distribution of gastrointestinal endocrine cells.

CONCLUSION

The ontogeny and development of NKA in rat duodenum mainly appear at 1 week before birth and at 4 weeks after birth, whereas the density of positive fiber in villus is not the same as adulthood until 60 days after birth. There are two key periods during the development of NKA in rat duodenum. The first crucial stage is from 1 week before birth to 1 week after birth. The second important stage is in the end of the 4th week after birth. The NKA-IR cells may be the endocrine cells that produce NKA in rat digestive tract. NKA may play an important role in the development of rat duodenum, and may be closely related to the functional establishment of duodenum.

Tachykinin neuropeptides in cerebellar granule neurons: an immunocytochemical study

We previously demonstrated that exogenously administered neurokinin A and neurokinin B, but not substance P, increased the sensitivity of cultured cerebellar granule neurons (CGNs) to glutamate. In the present study, the presence of tachykinin neuropeptides in CGNs was tested by confocal-based immunofluorescence. We found that neurokinin A and neurokinin B are present in CGNs but absent in astrocytes while substance P is abundant in astrocytes but absent in CGNs. It is postulated that the different localization of tachykinin neuropeptides in CGNs and astroglial cells has a physiological role in the modulation of excitatory transmission.

Effect of social isolation on ethanol consumption and substance P/neurokinin expression in Wistar rats

Environmental factors, such as adverse life experiences and family/peer influences have a substantial influence on the development of disorders related to alcohol use. In animals, maternal or peer separation/isolation has been used as an environmental intervention that has been shown to alter neurodevelopment and influence drinking behaviors in rodents and primates. In this study, the effects of adult peer isolation on subsequent ethanol intake were investigated in Wistar rats. Because central tachykinin levels have been reported to differ between rats selected for enhanced ethanol preference, neuropeptide [neurokinin A (NKA), substance P (SP)] concentrations were also estimated. Lower levels of ethanol intake, in a two-bottle free-choice model, were observed on the first day of forced ethanol drinking in the single-housed animals. However, overall ethanol consumption was unaffected by peer isolation. Peer isolation significantly lowered SP and NKA levels in the hypothalamus, but this effect was not related to ethanol consumption or body weight. These data indicate that endogenous SP and neurokinin levels are reduced by isolation housing, but this was not associated with alterations in drinking levels using a two-bottle choice procedure.

Immunohistochemical distribution of tachykinins in the CNS of the lamprey Petromyzon marinus

The presence of tachykinins in the CNS of vertebrates has been known for many decades, and numerous studies have described their distribution in mammals. Tachykinins were also reported in the CNS of lampreys using immunohistochemistry, chromatography, and radioimmunoassay methods, but the use of substance P (SP)-specific antibodies to reveal those tachykinins could have led to an underestimation of their number in this genus. Therefore, we carried out a new immunohistochemical study on Petromyzon marinus using a commercial polyclonal antibody that binds not only to mammalian SP, but also to other neurokinins. This antibody labeled all previously described lamprey tachykinin-containing neuronal populations, but more important, labeled new populations in several parts of the brain. These include the dorsal gray of the rostral spinal cord, the dorsal column nuclei, the octavolateral area, the nucleus of the solitary tract, the medial rhombencephalic reticular formation, the lateral tegmentum of the rostral rhombencephalon, the torus semicircularis, the optic tectum, the habenula, the mammillary area, the dorsal thalamic area, the lateral hypothalamus, and the septum area. Preabsorption experiments confirmed the binding of the antibody to neurokinins and allowed us to propose that the CNS of P. marinus contains at least two different tachykinins.

Mapping of neurokinin-like immunoreactivity in the human brainstem

BACKGROUND

Using an indirect immunoperoxidase technique, we have studied the distribution of immunoreactive fibers and cell bodies containing neurokinin in the adult human brainstem with no prior history of neurological or psychiatric disease.

RESULTS

Clusters of immunoreactive cell bodies and high densities of neurokinin-immunoreactive fibers were located in the periaqueductal gray, the dorsal motor nucleus of the vagus and in the reticular formation of the medulla, pons and mesencephalon. Moreover, immunoreactive cell bodies were found in the inferior colliculus, the raphe obscurus, the nucleus prepositus hypoglossi, and in the midline of the anterior medulla oblongata. In general, immunoreactive fibers containing neurokinin were observed throughout the whole brainstem. In addition to the nuclei mentioned above, the highest densities of such immunoreactive fibers were located in the spinal trigeminal nucleus, the lateral reticular nucleus, the nucleus of the solitary tract, the superior colliculus, the substantia nigra, the nucleus ambiguus, the gracile nucleus, the cuneate nucleus, the motor hypoglossal nucleus, the medial and superior vestibular nuclei, the nucleus prepositus hypoglossi and the interpeduncular nucleus.

CONCLUSION

The widespread distribution of immunoreactive structures containing neurokinin in the human brainstem indicates that neurokinin might be involved in several physiological mechanisms, acting as a neurotransmitter and/or neuromodulator.

An animal model to assess aversion to intra-oral capsaicin: increased threshold in mice lacking substance p

Despite the widespread consumption of products containing chemicals that irritate the oral mucosa, little is known about the underlying neural mechanisms nor is there a corresponding animal model of oral irritation. We have developed a rodent model to assess aversion to capsaicin in drinking water, using a paired preference paradigm. This method was used to test the hypothesis that the neuromodulator substance P (SP) plays a role in the detection of intra-oral capsaicin. 'Knockout' (KO) mice completely lacking SP and neurokinin A due to a disruption of the preprotachykinin A gene and a matched population of wild-type (WT) mice had free access to two drinking bottles, one containing water and the other capsaicin at various concentrations. Both KO and WT mice showed a concentration-dependent aversion to capsaicin. KO mice consumed significantly more capsaicin than WT at a single near threshold (1.65 microM) concentration, indicating that SP plays a limited role in the detection and rejection of oral irritants.

Transgenic mice overexpressing the growth-hormone-releasing hormone gene have high concentrations of tachykinins in the anterior pituitary gland

According to recent reports, substance P (SP) is localized in the anterior pituitary gland within subsets of thyrotropes and somatotropes, although earlier electron-microscopic studies described the presence of this tachykinin in mammotropes and gonadotropes. Transgenic mice overexpressing the growth-hormone-releasing hormone (GHRH) gene have markedly enlarged pituitary glands, due to hyperstimulation of the somatotropes. Therefore, we speculated that if somatotropes are able to synthesize tachykinins, these peptides should be greatly increased in the anterior pituitary of transgenic GHRH mice. We found that, in accordance with our working hypothesis, both SP and neurokinin A (NKA) were markedly increased in the anterior pituitary gland of male and female transgenic mice, compared with their respective normal controls. In male transgenic mice, NKA was 13.6- and SP 20.2-fold higher than in the anterior pituitary from normal mice. In female transgenic mice, NKA was 40- and SP 100-fold higher than in the anterior pituitary from normal female mice. In male transgenic mice, NKA and neuropeptide K (NPK) contents in the anterior pituitary showed no significant changes between 26 and 50 days of age but significantly increased between 50 days and 5 months of age. The concentration of NKA in the anterior pituitary did not show significant differences between 26 days and 5 months of age, but NPK concentrations in the anterior pituitary significantly decreased with age. In female transgenic mice, NKA content and concentration in the anterior pituitary increased after 35 days of age, but NPK concentrations significantly decreased after 26 days of age. Triiodothyronine markedly decreased anterior pituitary tachykinins, but ovariectomy and estrogen administration failed to significantly affect tachykinin concentrations in the anterior pituitary of transgenic mice. Tachykinin immunostaining was detected in some somatotropes, but tachykinins were also present in cells that were not GH positive. These findings indicate that hyperstimulated somatotropes contain increased stores of tachykinins and that these cells are a source of tachykinins in the anterior pituitary. Tachykinin stores in the anterior pituitary of transgenic mice were affected by thyroid hormones but seem to be insensitive to estrogens. The GHRH transgenic mice may be an interesting model to study the regulation of tachykinin stores in the anterior pituitary gland.

Hypoalgesia in mice with a targeted deletion of the tachykinin 1 gene

The tachykinin neuropeptides, substance P and substance K, are produced in nociceptive primary sensory neurons and in many brain regions involved in pain signaling. However, the precise role and importance of these neuropeptides in pain responses has been debated. We now show that mice that cannot produce these peptides display no significant pain responses following formalin injection and have an increased pain threshold in the hotplate test. On the other hand, the mutant mice react normally in the tail flick assay and acetic acid-induced writhing tests. These results demonstrate that substance P and/or substance K have essential functions in specific responses to pain.

Induction of tachykinin gene and peptide expression in guinea pig nodose primary afferent neurons by allergic airway inflammation

Substance P (SP), neurokinin A (NKA), and calcitonin gene-related peptide (CGRP) have potent proinflammatory effects in the airways. They are released from sensory nerve endings originating in jugular and dorsal root ganglia. However, the major sensory supply to the airways originates from the nodose ganglion. In this study, we evaluated changes in neuropeptide biosynthesis in the sensory airway innervation of ovalbumin-sensitized and -challenged guinea pigs at the mRNA and peptide level. In the airways, a three- to fourfold increase of SP, NKA, and CGRP, was seen 24 h following allergen challenge. Whereas no evidence of local tachykinin biosynthesis was found 12 h after challenge, increased levels of preprotachykinin (PPT)-A mRNA (encoding SP and NKA) were found in nodose ganglia. Quantitative in situ hybridization indicated that this increase could be accounted for by de novo induction of PPT-A mRNA in nodose ganglion neurons. Quantitative immunohistochemistry showed that 24 h after challenge, the number of tachykinin-immunoreactive nodose ganglion neurons had increased by 25%. Their projection to the airways was shown. Changes in other sensory ganglia innervating the airways were not evident. These findings suggest that an induction of sensory neuropeptides in nodose ganglion neurons is crucially involved in the increase of airway hyperreactivity in the late response to allergen challenge.

The effects of interleukin 1 beta on the hypothalamic tachykinin, neurokinin A

Interleukin-1 beta (IL-1 beta) is a pleiotropic cytokine that appears to be an integral component of the bidirectional signalling between the immune and central nervous systems. It is produced in the hypothalamus and has been shown to inhibit the hypothalamo-pituitary-gonadal axis and to activate the hypothalamo-pituitary-adrenal axis. IL-1 beta is reported to up-regulate the tachykinin, substance P (SP), in the peripheral nervous system. We have recently observed that members of the hypothalamic tachykinin family including SP, neurokinin A (NKA) and two N-terminal extended forms of NKA (neuropeptides kappa and gamma), inhibit hypothalamic LHRH and pituitary LH release and stimulate adrenal corticosterone secretion. The similarity in the endocrine effects of the tachykinins and the cytokine prompted us to test the hypothesis that IL-1 beta may stimulate the hypothalamic tachykinins, which would then mediate the neuroendocrine effects of IL-1 beta. First, the effects of IL-1 beta on the in vitro release of NKA-like immunoreactivity (NKA-li) from the hypothalamus was examined. Addition of 10 nM IL-1 beta significantly increased NKA-li release from the hypothalami of castrated rats, but not from the hypothalami of intact rats. To identify the site of IL-1 beta action, the effects of intraventricular IL-1 beta (100 ng) on NKA-li levels in various hypothalamic sites of intact and castrated rats were examined. The results showed that IL-1 beta increased NKA-li selectively in the median eminence (ME) and arcuate nucleus (ARC) of castrated rats only.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation, identification, and culture of normal mouse colonic glia

We have developed a novel method of isolating and culturing murine colonic mucosal glial cells. Two morphologies are appreciated, a small flat bi or tri polar cell and a larger multipolar cell. The glial cultures have been freed of contaminating fibroblasts and epithelial cells and have been passaged by trypsinization. By intermediate filament (IF) typing, the glial cells have been further characterized as astrocyte-like. All cells expressed glial fibrillary acid protein but not neurofilament 160 protein. The glial cultures expressed the neuropeptides, substance P and substance K. Central nervous system astrocytes synthesize neuropeptides, prostaglandins and cytokines, and can express major histocompatibility class II antigens. It is likely that enteric mucosal glia will also prove to have varied functions. These cultures can now be used to define the role of enteric mucosal glia and to further study their complex interaction with other cells of the colonic mucosa.

Nerve growth factor (NGF) regulates tachykinin gene expression and biosynthesis in rat sensory neurons during early postnatal development

The regulatory effects of nerve growth factor (NGF) on tachykinin biosynthesis in rat primary sensory neurons during the period of postnatal development were examined under in vivo and in vitro conditions. Administration of NGF to neonatal rats led to a significant increase in protein levels of substance P (SP) and neurokinin A (NKA) in trigeminal and dorsal root ganglia (DRG). In addition, Northern blot analysis revealed that preprotachykinin mRNA was upregulated in sensory ganglia of neonatal animals after treatment with NGF. Using a well-defined in vitro system for neonatal rat DRG and trigeminal ganglia neurons, we found that addition of NGF induced SP and NKA protein levels in a dose-dependent manner. Furthermore, preprotachykinin mRNA was markedly increased in cultured DRG and trigeminal ganglia neurons in the presence of NGF. Thus, our results clearly demonstrate that NGF regulates tachykinin gene expression and biosynthesis both in vivo and in vitro during the developmental period of rat sensory neurons.

Structural characterization of tachykinins (neuropeptide gamma, neurokinin A, and substance P) from a reptile, Alligator mississipiensis

An extract of the whole brain of the alligator (Alligator mississipiensis) contained very high concentrations of substance P-like immunoreactivity (405 pmol/g wet tissue) and neurokinin A-like immunoreactivity (514 pmol/g), as measured with antisera raised against the mammalian peptides. The primary structure of alligator substance P was established as: Arg-Pro-Arg-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2. This sequence is the same as that of chicken substance P and shows one substitution (Arg for Lys3) as compared with mammalian substance P. The neurokinin A-like immunoreactivity was separated into two components. Neuropeptide gamma was the most abundant peptide and its primary structure was established as Asp-Ala-Gly-Tyr-Gly-Gln-Ile-Ser-His-Lys-Arg-His-Lys-Thr-Asp-Ser- Phe-Val-Gly-Leu-Met-NH2. This sequence shows one substitution (Tyr for His4) compared with mammalian neuropeptide gamma. The second component was identical to mammalian neurokinin A. A peptide with the chromatographic properties of mammalian neuropeptide K was not identified in the extract.

Gene expression for peptides in neurons of the petrosal and nodose ganglia in rat

In situ hybridization was used to determine whether genes for neuropeptides [substance P/neurokinin A (SP/NKA), calcitonin gene-related peptide (CGRP), somatostatin (SOM), neuropeptide tyrosine (NPY) and cholecystokinin (CCK)] are expressed in inferior ganglia of the vagus (nodose) and glossopharyngeal (petrosal) nerves. Synthetic oligodeoxyribonucleotides, complementary to the cognate, mRNAs were labeled with [32P] or [35S], and hybridized to 10 microns thick sections of unperfused tissue which were then processed for film and emulsion autoradiography. We found numerous, clustered neuronal perikarya throughout the nodose and petrosal ganglia that expressed preprotachykinin A (SP/NKA) and CGRP mRNAs to varying degrees. Neurons expressing preproSOM mRNA were less abundant and more scattered throughout both ganglia. Notably, we found mRNA for NPY in cells (usually 5-10 per section) in both ganglia. To our knowledge, this is first evidence for NPY in these sensory ganglia. In contrast to previous immunohistochemical findings, we found no evidence for expression of preproCCK in either the nodose or petrosal ganglia. The present findings demonstrate that cells of the nodose and petrosal ganglia express the genes for a number of neuropeptides that are presumably involved with transmission of visceral sensory afferent information to higher order neurons of the central nervous system.

Expression and cellular localization of substance P/neurokinin A and neurokinin B mRNAs in the rat retina

The mammalian tachykinin peptides, substance P (SP), neurokinin A (NKA), and neurokinin B (NKB) are encoded by distinct mRNAs derived from separate preprotachykinin (PPT) genes. The SP/NKA-encoding PPT gene generates three mRNAs by alternative RNA processing: alpha-PPT mRNA, which encodes SP only, and beta- and gamma-PPT mRNAs, which encode both SP and NKA. The NKB-encoding PPT gene generates mRNAs that produce NKB. The distribution and cellular localization of SP, NKA and NKB mRNAs in the rat retina were studied by RNA blot and in situ hybridization techniques. Blot hybridization analysis of retinal RNA extracts with [32P]-labeled RNA probes complementary to SP/NKA and NKB mRNAs demonstrated single bands of hybridization at 1300 and 900 bases, respectively. Solution hybridization-nuclease protection experiments showed multiple SP/NKA-encoding transcripts with relative levels of gamma-PPT mRNA greater than beta-PPT mRNA much greater than alpha-PPT mRNA. In situ hybridization histochemistry with [35S]-labeled antisense RNAs demonstrated that SP/NKA-encoding transcripts are expressed in small-to-medium somata located in the proximal inner nuclear, inner plexiform, and ganglion cell layers, whereas NKB-encoding transcripts are expressed in small-to-medium somata located only in the ganglion cell layer. In this layer, cells containing NKB mRNAs are more numerous than those containing SP/NKA mRNAs. Only background labeling was observed in sections incubated with sense RNA probes, pretreated with RNase A prior to hybridization or incubated in hybridization buffer without the labeled probe. Immunohistochemical studies with a monoclonal antibody directed to the conserved COOH-terminal sequence of the tachykinin peptides revealed tachykinin-like immunoreactive somata with similar size and distribution to those containing SP/NKA- and NKB-encoding transcripts. These results indicate that both SP/NKA and NKB mRNAs are present in the rat retina and that the PPT genes are differentially expressed in specific cell populations. The size and distribution of these cells suggest that they are amacrine and displaced amacrine cells, however, the possibility that tachykinins are present also in ganglion cells in the rat retina cannot be ruled out.