Nitrergic Neurons in the Spinal Cord of the Bottlenose Dolphin (Tursiops truncatus)

Nitric oxide (NO) is a freely diffusible gaseous neurotransmitter generated by a selected population of neurons and acts as a paracrine molecule in the nervous system. NO is synthesized from l ‐arginine by means of the neuronal nitric oxide synthase (nNOS), an enzyme requiring nicotine adenine dinucleotide phosphate (NADPH) as cofactor. In this study, we used histochemical and immunohistochemical techniques to investigate the distribution of NADPH‐diaphorase (NADPH‐d) and nNOS in the spinal cord of the bottlenose dolphin (Tursiops truncatus). Cells with a fusiform‐shaped somata were numerous in the laminae I and II. The intermediolateral horn showed darkly‐stained cells with a multipolar morphology. Neurons with a multipolar or fusiform morphology were observed in the ventral horn. Multipolar and fusiform neurons were the most common cell types in lamina X. Nitrergic fibers were numerous especially in the dorsal and intermediolateral horns. The presence of nitrergic cells and fibers in different laminae of the spinal cord suggests that NO may be involved in spinal sensory and visceral circuitries, and potentially contribute to the regulation of the complex retia mirabilia. Anat Rec, 296:1603–1614, 2013. © 2013 Wiley Periodicals, Inc.     

The morphology and distribution of peptide-containing neurons in the adult and developing visual cortex of the rat. I. Somatostatin

Summary Using conventional immunocytochemical techniques, we have examined the morphology and distribution of somatostatin-like immunoreactive neurons in the visual cortex of albino rats between the first postnatal day and maturity. In the adult, somatostatin-immunoreactive neurons were observed in layers II to VI but were concentrated in layers II and III. These cells displayed morphological features characteristic of the multipolar and bitufted varieties of cortical non-pyramidal neurons as described in Golgi preparations of rat visual cortex.On the first postnatal day and in the subsequent few days, immunoreactivity was confined to immature bipolar and multipolar neurons concentrated in layers V and VI. Labelled cells first appeared in the more superficial layers at the beginning of the second postnatal week and attained a distribution similar to that observed in adult animals at the end of this week. At this time they closely resembled their adult counterparts from which they appeared indistinguishable by the end of the third postnatal week. The late appearance of labelled cells in the superficial layers, where they are predominantly located in adult animals, suggests that the somatostatin immunoreactivity exhibited by most of these neurons develops several days after they have completed their migration and assumed their positions in the visual cortex.     

The morphology and distribution of peptide-containing neurons in the adult and developing visual cortex of the rat. IV. Avian pancreatic polypeptide

Summary Immunocytochemical techniques were used to investigate the morphology and distribution of avian pancreatic polypeptide-like immunoreactive neurons in the visual cortex of albino rats at various ages from the first postnatal day to adulthood. In the adult, immunoreactive neurons were located in layers II to VI but were somewhat concentrated in the deeper cortical layers. The overwhelming majority of labelled cells exhibited morphologies characteristic of multipolar, bitufted and bipolar varieties of non-pyramidal neurons as described in Golgi preparations of rat visual cortex. However, a few immunoreactive pyramidal neurons were also observed.On the first postnatal day, a small number of immature non-pyramidal neurons were observed in the subplate region. Labelled cells appeared in the more superficial layers at the beginning of the second postnatal week and attained a distribution similar to that observed in adult animals during the third week. The morphological maturation of immunoreactive neurons occurred gradually during the first two postnatal weeks and at day 21, they appeared qualitatively indistinguishable from their adult counterparts.     

大鼠心肌氮能神经元及纤维的分布

目的　观测大鼠心脏各部心肌一氧化氮合酶 (nNOS)免疫阳性神经元的形态及分布 ,为探讨氮能神经在心肌的作用提供形态学资料。方法　采用免疫组织化学SABC法显示大鼠心脏nNOS免疫阳性神经元及神经纤维的形态与分布。结果　在大鼠各部心肌内均有氮能神经元和神经纤维分布 ,胞体呈多种形状。nNOS免疫阳性神经纤维呈串珠状、条索状、细线状及不定形状 ,其走行多与肌纤维长轴平行。氮能神经元及纤维的数密度和面密度心房高于心室 ,6月龄高于 1月龄组 (P <0 .0 1)。结论　各部心肌均有氮能神经元及神经纤维 ,心房的含量高于心室。     

Prenatal effects of retinoic acid on lumbar spinal cord development and liver antioxidants in rats

During embryonic and early postnatal development, retinoic acid (RA) regulates genes that control neuronal differentiation and neurite outgrowth from the neural tube. The effects of high levels of RA on the CNS can be detected via nitric oxide (NO), which plays a crucial role in neural transmission. The aim of the study was to investigate the prenatal influence of high levels of RA on postnatal development of nitrergic structures in lumbar spinal cord and antioxidant status. RA was administered orally at a dose of 10 mg/kg body weight to pregnant female Wistar rats during days 8–10 of gestation. Neuronal nitric oxide synthase (nNOS) of lumbar spinal cord sections was processed for visualization via nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry on postnatal day one, day twenty-one and in adults. The results suggest that prenatal administration of high levels of RA is not associated with postnatal morphological changes in nNOS-positive neurons in the rat lumbar spinal cord. An estimation of the activity of enzymes related to the storage of retinoid in the liver showed possible side effects. Suppression and deepening of superoxide dismutase activity persisted into adulthood, and a concurrent downregulation of glutathione reductase was noted. A decrease in reduced glutathione persisted until adulthood when other compensatory mechanisms were probably active to maintain an appropriate level.     

Anatomical evidence of non-parasympathetic cardiac nitrergic nerve fibres in rat

Neuronal nitric oxide synthase (nNOS)-derived nitric oxide (NO) plays a major role in the neural control of circulation and in many cardiovascular diseases. However, the exact mechanism of how NO regulates these processes is still not fully understood. This study was designed to determine the possible sources of nitrergic nerve fibres supplying the heart attempting to imply their role in the cardiac neural control. Sections of medulla oblongata, vagal nerve, its rootlets and nodose ganglia, vagal cardiac branches, Th₁-Th₅ spinal cord segments, dorsal root ganglia of C₈-Th₅ spinal nerves, and stellate ganglia from 28 Wistar rats were examined applying double immunohistochemical staining for nNOS combined with choline acetyltransferase (ChAT), peripherin, substance P, calcitonin gene-related peptide, tyrosine hydroxylase or myelin basic protein. Our findings show that the most abundant population of purely nNOS-immunoreactive (IR) neuronal somata (NS) was observed in the nodose ganglia (37.4 ± 1.3%). A high number of nitrergic NFs spread along the vagal nerve and entered its cardiac branches. All nitrergic neuronal somata (NS) in the nucleus ambiguus were simultaneously immunoreactive (IR) to ChAT and composed only a small subset of neurons (6%). In the dorsal nucleus of vagal nerve, biphenotypic nNOS-IR/ChAT-IR neurons composed 7.0 ± 1.0%, while small purely nNOS-IR neurons were scarce. Nitrergic NS were plentifully distributed within the nuclei of solitary tract. In the examined dorsal root and stellate ganglia, a few nitrergic NS were sporadically present. The majority of sympathetic NS in the intermediolateral nucleus were simultaneously immunoreactive for nNOS and ChAT. In conclusion, an abundant population of nitrergic NS in the nodose ganglion implies that neuronal NO is involved in afferent cardiac innervation. Nevertheless, nNOS-IR neurons identified within vagal nuclei may play a role in the transmission of preganglionic parasympathetic nerve impulses.     

Cytochemical correlates of the sleep-wake interface: concerted expression of brain-derived nitric oxide synthase (bNOS) and the nicotinic acetylcholine receptor (nAChR) in a columnoid organization of the primate prefrontal cortex

Nitric oxide (NO) was recently proposed to be involved in the sleep-wake cycle and cortical spreading depression. As a structural correlate of these functions, we found that bNOS IR was expressed by three cell types in the prefrontal cortex, viz. bipolar, multipolar, and stellate cells. Dendrites of bipolar cells established bundles resulting in a columnoid organization; in addition, the monoclonal antibody mAb 35 which labels subunits alpha1, alpha3 and alpha5 of nAChR, also visualized apical axons proceeding alongside the columnoids. In contrast, alpha-bungarotoxin which labels the alpha7-subunit of nAChR, visualized only perikarya of interneurons from where the apical axons arose. In the prefrontal cortex of monkeys which were anesthetized for 6-24 hours, only traces of the columnoid organization were found, while perikaryal bNOS and nAChR were invariably expressed. It is suggested that interactions between NO and presynaptically released ACh might be involved in cortical functions such as the sleep/wake cycle.     

大鼠视觉中枢生后发育过程中的一氧化氮合酶阳性神经元的形态及分布变化

本文用NADPH-黄递酶组织化学技术研究了生后不同年龄段（0、7、14、21、28、35、60、120d）Wistar大鼠视皮层（17区）和上丘表层中一氧化氮合酶阳性神经元的形态及分布的变化。结果表明：视皮层17区中的一氧化氮合酶阳性神经元在生后7d时开始出现，但胞体小，树突分枝少而短，以双极细胞为主，占68.0％;14d时数量达到高峰;且14～21d中，该神经元胞体截面积明显增大，树突分枝复杂化，长度增加，多极细胞占64％;28d后一氧化氮合酶阳性神经元胞体面积，树突分枝长度明显减小，分枝简单化;35d后接近成年动物水平（120d）.生后7d时，一氧化氛合酶阳性神经元主要位于视区的白质和皮层的5、6层中，7d后该神经元及神经纤维在第2／3及4层中明显增多，这种分布状态在35d后趋于稳定。上丘表层中的一氧化氮合酶阳性细胞在生后第2周逐渐出现，第3周迅速增加，第4周达最大值，以后下降并趋于稳定水平。结果提示：大鼠生后发育过程中视觉中枢的一氧化氮合酶阳性神经元数量及形态变化与视觉发育的可塑性有关。     

Histochemical demonstration of NADPH-diaphorase activity, a marker for nitric oxide synthase, in neurons of the rat pancreas.

To clarify the role of nitric oxide (NO) in the pancreas, we histochemically investigated NADPH-diaphorase, a marker for NO synthase, in the rat pancreas. NADPH-diaphorase activity was localized in the neurons and endothelium of vessels. The nerve fibers with NADPH-diaphorase activity were observed in both the exocrine and the endocrine pancreas associated chiefly with the vascular systems. Most nerve cell bodies (98.5%) within the pancreatic parenchyma showed strong activity for this enzyme. These results suggest that NO may participate in the hemodynamic control of the pancreas and in the neuronal regulation of pancreatic exocrine and endocrine functions.     

Chronic Alcohol Consumption Affects Gastrointestinal Motility and Reduces the Proportion of Neuronal NOS‐Immunoreactive Myenteric Neurons in the Murine Jejunum

Alcohol consumption interferes with gastrointestinal transit causing symptoms in alcoholic patients. Nitric oxide (NO), synthesized by neuronal nitric oxide synthase (nNOS) plays an important role in the control of gastrointestinal motility. Our aim was to investigate whether chronic alcohol intake in a murine model induces gastrointestinal motility disturbances and affects the nitrergic myenteric neurons in the stomach and jejunum. Gastric emptying, small intestinal transit and geometric centre were measured in vivo after intragastric gavage of Evans blue. Nitrergic relaxations to electrical field stimulation (EFS) and exogenous NO were recorded in jejunal muscle strips in vitro. The proportion of nNOS‐immunopositive myenteric neurons was assessed using PGP9.5 and nNOS immunostaining. After chronic alcohol consumption, gastric emptying and small intestinal transit were delayed compared with control mice, and the nitrergic nerve‐mediated relaxations to EFS in the jejunum were decreased, whereas relaxations to exogenous NO did not differ. The proportion of nNOS‐immunoreactive neurons did not change in the stomach, whereas in the jejunum the percentage decreased from 33% to 27% (P < 0.001) after chronic alcohol intake. The total number of myenteric neurons remained unchanged. These results suggest that chronic alcohol consumption disturbs gastric and small intestinal motility in vivo and in vitro and is associated with a decrease in the proportion of nNOS‐immunoreactive myenteric neurons in the murine jejunum. Anat Rec 293:1536–1542, 2010. © 2010 Wiley‐Liss, Inc.     

Developmental changes of nitric oxide synthase expression in the rat hypothalamoneurohypophyseal system

The present study investigated the immunohistochemical localization of neuronal nitric oxide synthase (nNOS) in the hypothalamoneurohypophyseal system (HNS) of the developing rats on postnatal day 1 (PN1), 7 (PN7), 14 (PN14), 21 (PN21), and the adult rats. The nNOS-positive neurons were not discernable in the supraoptic nucleus (SON), the paraventricular nucleus (PVN), and the median eminence (ME) at PN1 and PN7. A few neurons positive for nNOS were first detected at PN14. At PN21, the nNOS-positive cells in SON and PVN rapidly increased in number. The pattern of nNOS expression at this stage approached that of the adult. Moreover, the increase of nNOS expression in the SON and PVN during the postnatal period was accompanied by the maturation of arginine vasopressin (AVP) and oxytocin (OT) neurons as indicated by the number and size of OT or AVP neurons in the SON and PVN. The patterns of AVP versus OT expression also reached that of the adult by the end of the third postnatal week. The time course of the change in nNOS expression coincided with the maturation of AVP and OT neurons in the HNS and suggested that NO synthesized by conversion of NOS is involved in the modulation of activity of neurons in the SON and PVN of the HNS.     

Low and infrequent expression of nitric oxide synthase/NADPH-diaphorase in neurons of the human supraoptic nucleus: a histochemical study

The gas nitric oxide is a messenger in brain signaling. In the hypothalamo-hypophyseal system nitric oxide is involved in the control of the expression and/or release of peptide hormones (corticotropin-releasing hormone, gonadotropin-releasing hormone, vasopressin and oxytocin). Nitric oxide synthase (NOS), the enzyme generating nitric oxide, is abundantly present in the magnocellular nuclei of the rat hypothalamus. Its localization in the human hypothalamus is less well studied. Hence, we investigated the anatomical distribution of neuronal nitric oxide synthase in the human supraoptic nucleus by use of immunohistochemical and enzyme histochemical techniques. The immunohistochemical localization of NOS was studied in 31 matched human hypothalami (13 control cases, eight depressed patients and ten schizophrenics). NADPH-diaphorase studies were carried out on seven additional hypothalami (three normal brains, four schizophrenics). Apparent inter-individual differences exist with regard to the occurrence of the enzyme in supraoptic neurons. In a majority of cases no immunostaining or histochemical reaction for the enzyme was observed. In seven cases (three controls, two schizophrenics, two depressives) a population of nitrergic nerve cells was seen in the dorsomedial part of the nucleus. This group of cells also stained for NADPH-diaphorase. Also, there were a few NOS-immunopositive neurons scattered throughout the nucleus. Additionally, thin NADPH-diaphorase positive fibers were observed to cross the nucleus. Our data show that, unlike the rat, the human supraoptic nucleus contains only a small number of nitrergic neurons. No correlation was found between the expression of the enzyme in supraoptic neurons and the psychiatric status of the patients.     

Nitrergic and peptidergic innervation in the developing rat heart

The phenotypic expression and anatomic distribution of nitrergic and peptidergic innervation in the developing rat heart was localized by reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry and immunohistochemistry using antibodies against neuronal isoform of nitric oxide synthase (nNOS), neuropeptide Y (NPY) and calcitonin-gene-related peptide (CGRP). NPY-immunoreactive nerve fibers showed the earliest expression by 16 days of gestation, with preferential innervation of the nodal and perinodal areas, followed by the innervation of the valves and ventricles by postnatal day 7. NPY immunoreactivity was also localized to a large proportion of the intrinsic cardiac ganglia from 16 days of gestation onwards with a progressive increase in the number of neuronal cell bodies per ganglia with age. CGRP-positive nerve fibers appeared by 19 days of gestation and were less dense during the gestational and early postnatal periods, and showed a quantitative increase in density by 7 days, followed by a decrease by 3 weeks postnatal. None of the intrinsic ganglia were stained positive for CGRP, indicating the extrinsic sensory origin of these stained fibers. Nitrergic innervation paralleled the sensory innervation, with the cardiac ganglia and nerve fibers showing a positive labeling from 19 days of gestation onwards. NADPH-d and nNOS were partially co-localized. Double-label immunohistochemistry showed that a considerable proportion of sensory CGRP-immunopositive fibers were also immunoreactive for NOS. The results of the present study show that neuropeptides and nitric oxide are expressed by the late gestational period and that autonomic efferent innervation precedes sensory and nitrergic innervation in the developing heart. Accepted: 4 January 2000     

人胎舌内氮能神经元发育的形态学研究

目的：探讨人胎舌内氮能神经元的发育。方法：用NADPH－d组织化学法对人胎舌内氮能神经元的分化、迁移和生长发育进行观察。结果：T经4个月胎龄时,舌上皮组织中层圆形细胞分化形成酸的氮能神经细胞,并从上皮细胞向上皮下层和肌组织迁移。神经细胞体较小,NOS阳性反应较弱,其生长发育过程可分为两个时期,从第4－7个月龄末为生长发育期,神经元胞体由小逐渐增,数目增加,NOS阳性反应逐渐增强,至第7个月龄时,处于生长发育的高峰。其形态特征：由酸形发育成蝌蚪形,之后形成多样性形态,第8－10个月龄为成熟期,表现为氮能神经元胞体较大,NOS呈强阳性反应。在上皮下 支和肌组织内氮能神经元呈散在分布,有的部位聚集成明显的舌内神经节,结论：舌内氮能神经元来源于胚胎早期舌的上皮组织,通过分化,迁移,增殖和生长发育形成氮能神经元。     

Developmental regulation of brain nitric oxide synthase expression in the ferret thalamic reticular nucleus

We have found that cells in the ferret thalamic reticular nucleus (TRN) express brain nitric oxide synthase (bNOS) in a transient pattern during early postnatal development. Similar to our previous findings in the lateral geniculate nucleus (LGN), bNOS expression in the TRN is first observed at postnatal day 7 (P7) and continues to P35. Quantitative measures show a significant change in the relative numbers of bNOS+ cells from P7–P35, and suggest there is a transition in morphology from a bipolar shape with two primary dendrites, to a more complex, multipolar arrangement. During TRN development, the pattern of bNOS expression shifts from the somatodendritic localization seen during the first postnatal month to expression within axon fibers in the adult. Expression of bNOS within TRN cells demonstrates an additional source of nitric oxide in the developing visual thalamus, perhaps indicating a common function for thalamic nitergic neurons as cellular mediators in the establishment of central topography both in the LGN and the TRN.     

大鼠食管肌间神经元nNOS与calbindin的共存及其与衰老关系的研究(英文)

本实验通过观察一氧化氮合酶(nNOS)与细胞内钙结合蛋白(calbindin, CB)共存情况,旨在研究大鼠食管内NO类神经元的神经化学特性并试图寻找出引起食管NO类神经元在衰老过程中丢失的可能原因。取自不同年龄组及种系(Wistar和S-D)大鼠的食管组织,制成肌间神经丛铺片,经nNOS与CB免疫组化双重染色后在荧光显微镜下观察。结果显示,nNOS与CB的免疫阳性反应物均见于大鼠食管肌间神经元胞体内。根据二者共存情况,大鼠食管内nNOS免疫阳性神经元可分为两大亚类:nNOS+/CB+及nNOS+/CB-。而且我们首次发现在大鼠食管腹腔段含有大量nNOS+/CB+神经元,约占NO类神经元总体的30% ~40%,与食管其它部位相比有显著差异(P<0.001)。另外,大鼠食管腹腔段绝大多数CB免疫阳性神经元同时也为nNOS免疫阳性(约占95% ~100%)。上述特征均见于本实验所观察的所有不同年龄及不同种系的大鼠食管内。在大鼠衰老过程中,nNOS+/CB+神经元的相对百分比的变化具有种系特异性。线形回归实验分析表明:年轻SD大鼠食管内nNOS+/CB+神经元的百分比含量与衰老过程中NO类神经元丢失数量的百分比之间存在显著负相关性(correlation coefficient 0.99;P<0.05)。结果提示在S-D大鼠衰老过程中其食管内NO类神经元的丢失可能与其细胞内钙结合蛋白含量的变化有关。但nNOS/CB共存神经元在分布上有明显差异的生物学意义尚有待于进一步研究。     

NANC nerves in the respiratory air sac and branchial vasculature of the Indian catfish,Heteropneustes fossilis

Gill and air sac of the Indian catfish Heteropneustes fossilis harbour a nerve network comprising an innervated system of neuroepithelial endocrine cells; the latter cells are found especially in the gill. A series of antibodies was used for the immunohistochemical detection of neurotransmitters of the neural non-adrenergic, non-cholinergic (NANC) systems such as the sensory neuropeptides (enkephalins), the inhibitory neuropeptide VIP and neuronal nitric oxide synthase (nNOS) responsible for nitric oxide (NO) production which is an inhibitory NANC neurotransmitter. NADPH-diaphorase (NADPH-d) histochemistry was used as marker of nNOS although it is not a specific indicator of constitutively-expressed NOS in gill and air sac tissues. A tyrosine hydroxylase antibody was used to investigate adrenergic innervation. Nitrergic and VIP-positive sensory innervation was found to be shared by gill and air sac. Immunohistochemistry revealed the presence of enkephalins, VIP, NOS and NADPH-d in nerves associated with branchial and air sac vasculature, and in the neuroendocrine cell systems of the gill. Adrenergic nerve fibers were found in some parts of the air sac vasculature. The origin of the nerve fibers remains unclear despite previous findings showing the presence of both NADPH-d and nNOS in the sensory system of the glossopharyngeal and vagus nerves including the branchial structure. Scarce faintly stained nNOS-positive neurons were located in the gill but were never detected in the air sac. These findings lead to the conclusion that a postganglionic innervation of the airways is absent. Mucous goblet cells in the gill were found to express nNOS and those located in the non-respiratory interlamellar areas of the air sac were densely innervated by nNOS-positive and VIP-positive nerve fibers. Our immunohistochemical studies demonstrate that most arteries of the gill and air sac share a NANC (basically nitrergic) innervation which strongly suggests that they are homologous structures.     

The morphology and distribution of peptide-containing neurons in the adult and developing visual cortex of the rat. II. Vasoactive intestinal polypeptide

Summary Using immunocytochemistry, we have examined the morphology and distribution of vasoactive intestinal polypeptide-like immunoreactive neurons in the visual cortex of albino rats whose ages were closely spaced in time between the first postnatal day and adulthood. In the adult, immunoreactive neurons were located in layers II to VI but were concentrated in layers II and III. All labelled neurons had the morphological characteristics of cortical non-pyramidal cells with the majority being of the bipolar variety as described in Golgi preparations. Some multipolar forms were also present.Vasoactive intestinal polypeptide-immunoreactivity appeared to develop in postnatal life. Labelled cells were first seen in layers V and VI at day 4. During the subsequent few days, some labelled cells were observed in the more superficial layers and by day 8 they were predominantly present in layers II and III. Although the distribution of immunoreactive cells at this time resembled that of adult animals, their morphology displayed immature features. The size and extent of their dendritic branching appeared to increase considerably during the second and third weeks and their morphological maturation was attained by the middle of the fourth postnatal week.     

Co-localization of corticotropin-releasing hormone with glutamate decarboxylase and calcium-binding proteins in infant rat neocortical interneurons

 Corticotropin releasing hormone (CRH) has been localized to interneurons of the mammalian cerebral cortex, but these neurons have not been fully characterized. The present study determined the extent of co-localization of CRH with glutamate decarboxylase (GAD) and calcium-binding proteins in the infant rat neocortex using immunocytochemistry. CRH-immunoreactive (ir) neurons were classified into two major groups. The first group was larger and consisted of densely CRH-immunostained small bipolar cells, predominantly localized to layers II and III. The second group of CRH-ir cells was lightly labeled and included multipolar neurons mainly found in deep cortical layers. Co-localization studies indicated that the vast majority of CRH-ir neurons, including both bipolar and multipolar types, was co-immunolabeled for GAD-65 and GAD-67. Most multipolar, but only some bipolar, CRH-ir neurons also contained parvalbumin, while CRH-ir neurons rarely contained calbindin or calretinin. These results indicate that virtually all CRH-ir neurons in the rat cerebral cortex are GABAergic. Furthermore, since parvalbumin is expressed by cortical basket and chandelier cells, the colocalization of CRH and parvalbumin suggests that some cortical CRH-ir neurons may belong to these two cell types. Received: 15 April 1998 / Accepted: 16 June 1998     

The neuronal nitric oxide synthase (nNOS) gene contributes to the regulation of tyrosine hydroxylase (TH) by cocaine

Recently, we demonstrated that intact nitric oxide (NO) signaling is essential for the development of cocaine behavioral sensitization in adulthood [M.A. Balda, K.L. Anderson, Y. Itzhak, Differential role of the nNOS gene in the development of behavioral sensitization to cocaine in adolescent and adult B6;129S mice, Psychopharmacology (Berl) 200 (2008) 509–519]. Given the requirement of dopamine (DA) transmission in cocaine-induced behavioral sensitization and the interactions between NO and DA systems, the present study investigated the role of the neuronal nitric oxide synthase (nNOS) gene and the effect of cocaine on the expression of tyrosine hydroxylase (TH)-immunoreactive (-ir) neurons. Adult (postnatal day 80) wild type (WT) and nNOS knockout (KO) mice received saline or a sensitizing regimen of cocaine (20 mg/kg) for 5 days. After 24 h, TH immunoreactivity was assessed in the ventral tegmental area (VTA) and the dorsal striatum (dST) using stereology and Western blotting, respectively. We report that (a) nNOS KO mice express lower levels of TH-ir neurons in the VTA compared to WT counterparts, (b) cocaine administration to WT mice significantly increased striatal TH expression, and (c) the same cocaine administration to nNOS KO mice significantly decreased striatal TH expression. Thus, the nitrergic system may contribute to cocaine-induced behavioral sensitization by regulating dopaminergic neurotransmission.