Age-related changes in oxytocin-, arginine vasopressin- and nitric oxide synthase-expressing neurons in the supraoptic nucleus of the rat

Many histochemical investigations indicated that the oxytocin (OXY), the arginine vasopressin (AVP) and the nitric oxide synthase (NOS) have been synthesized in the supraoptic nucleus (SON) neurons. The objective of this study was to examine the age-related expression of the OXY, the AVP and the NOS in the SON of the young adult (2-month-old) and the aged (24-month-old) rats. The histochemistry for reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d; marker for the NOS) and the double labeling histochemistry for the OXY/NADPH-d or the AVP/NADPH-d were employed, and the quantitative analysis was performed with a computer-assisted image processing system. In comparison of the young adult and the aged group, the cell number, the cell size and the reactive density of the NOS-expressing neurons showed a significant increase along with age, and these evidences suggested the age-related increase of the nitric oxide (NO) production. The age-related significant increase was not detected in the number of the OXY/NOS-expressing neurons in the dorsal part, but was detected in the number of the AVP/NOS-expressing neurons in the ventral part. Based on our histochemical findings and reports demonstrated by other authors, we attempted to discuss the physiological role of NOS for the secretion of posterior pituitary hormones along with age.     

Distribution of NADPH-diaphorase and nitric oxide synthase in the trigeminal ganglion and mesencephalic trigeminal nucleus of the cat. A histochemical and immunohistochemical study

The trigeminal ganglion (TrG) and mesencephalic trigeminal nucleus (MTN) neurons are involved in the transmission of orofacial sensory information. The presence of nitric oxide (NO), a putative neurotransmitter substance in the nervous system, was examined in the cat TrG and MTN using nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry and nitric oxide synthase (NOS) immunohistochemistry. In the TrG, where the majority of the trigeminal primary afferent perikarya are located, most of the intensely NADPH-d/ NOS-stained cells were small in size and distributed randomly throughout the ganglion. The medium-sized neurons were moderately stained. A plexus of pericellular varicose arborizations around large unstained ganglion cells and densely stained fibers in-between could also be observed. In the caudal part of the MTN, both NADPH-d activity and NOS immunoreactivity was present in MTN neurons. In addition, a few scattered NADPH-d/NOS-containing neurons were found in the mesencephalic-pontine junction part of the nucleus. In contrast, only nerve fibers and their terminals were present at a more rostral level in the mid- and rostral MTN. MTN neuronal perikarya were enveloped in fine basket-like NADPH-d/ NOS-positive networks. Differential expression patterns of NOS and its marker NADPH-d suggest that trigeminal sensory information processing in the cat MTN is controlled by nitrergic input through different mechanisms. We introduce the concept that NO can act as a neurotransmitter in mediating nociceptive and proprioceptive information from periodontal mechanoreceptors but may also participate in modulating the activity of jaw-closing muscle afferent MTN neurons.     

Differential histochemical localization patterns of reduced nicotinamide adenine dinucleotide phosphate-diaphorase and neuronal nitric oxide synthase during postnatal development of the rat vomeronasal organ

The present study was undertaken to examine the localization patterns of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) by enzyme histochemistry and neuronal nitric oxide synthase (NOS) by immunohistochemistry in the vomeronasal organ of rat from postnatal day 0 for 8 weeks (adult). Nicotinamide adenine dinucleotide phosphate-diaphorase activity was not observed in the sensory epithelium of the vomeronasal organ at postnatal day 0 (the day of birth) and at day 1. At postnatal day 2, NADPH-d activity was observed in several vomeronasal neurons and on the surface of the sensory epithelium. From 25 days through adulthood, the number of vomeronasal neurons having NADPH-d activity increased gradually. On the other hand, neuronal NOS immunoreactivity was not observed in the sensory epithelium of the vomeronasal organ in newborns or in the adult rat. In this study, it is suggested that the nitric oxide pathway in the sensory epithelium of the vomeronasal organ comes into play beyond postnatal day 3. Moreover, it was found that NADPH-d and neuronal NOS are not colocalized in the sensory epithelium of the developing rat vomeronasal organ.     

Distribution of heme oxygenase-2 and NADPH-diaphorase in the spinal trigeminal nucleus of the rat

Heme oxygenase (HO)/carbon monoxide (CO) and nitric oxide synthase (NOS)/nitric oxide (NO) systems are involved in sensory information processing. The present study was undertaken to examine the distribution of HO-2 and NOS in the spinal trigeminal nucleus (STN) of the rat, using histochemistry and immunohistochemistry. Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) staining was found that NADPH-d activity was more prominent in the nucleus caudalis (Vc) and the dorsomedial subdivision of the nucleus oralis (Vo) than in other spinal trigeminal regions. Immunohistochemistry for HO-2 revealed that HO-2 staining neurons distributed extensively, which intensity was higher in the rostral than caudal part of the STN. The colocalization of NADPH-d and HO-2 was mainly confined in the Vc. The expression and distribution of NADPH-d and HO-2 suggest that NO and CO are likely neurotransmitters and might function in the processing orofacial signal in the STN together.     

Localization of nitric oxide synthase in canine ileocolonic and pyloric sphincters

The distribution of neurons containing NADPH-diaphorase (NADPH-d) activity and nitric oxide synthase-like immunoreactivity (NOS-LI) in the canine pyloric and ileocolonic sphincters was studied. Cells within the myenteric and submucosal ganglia were positive for NADPH-d. These cells generally had the morphology of Dogiel type-I enteric neurons, however, there was some diversity in the morphology of NADPH-d-positive neurons in the myenteric plexus of the pylorus. Intramuscular ganglia were observed in both sphincters, and NADPH-d was found in a sub-population of neurons within these ganglia. Dual staining with an antiserum raised against nitric oxide synthase (NOS) demonstrated that almost all cells with NOS-LI were also NADPH-d positive. Varicose fibers within ganglia and within the circular and longitudinal muscle layers also possed NOS-LI and NADPH-d activity. Dual staining with anti-VIP antibodies showed that some of the NADPH-d-positive cells in the myenteric and submucosal ganglia also contained VIP-LI, but all VIP-LI-positive cells did not express NADPH-d activity. These data are consistent with recent physiological studies suggesting that nitric oxide serves as an inhibitory neurotransmitter in the pyloric and ileocolonic sphincters. The data also suggest that VIP is expressed in a sub-population of NADPH-d-positive neurons and may therefore act as a co-transmitter in enteric inhibitory neurotransmission to these specialized muscular regions.     

锌对急性缺氧小鼠海马NOS和nNOS水平的影响

目的：观察锌对急性缺氧小鼠海马一氧化氮合酶（nitric oxide synthase,NOS）和神经元型一氧化氮合酶（neuronal NOS,nNOS）阳性神经元的影响,以探讨锌抗脑缺氧的作用机制。方法：复制小鼠急性缺氧模型,采用NADPH-d组织化学和nNOS免疫组织化学方法,研究给锌组和不给锌组急性缺氧小鼠海马各分区NOS和nNOS阳性神经元数量的变化。结果：给锌组比不给锌组小鼠缺氧耐受时间显著延长,差异有显著性（P〈0．05）;海马及其CA1区NOS和nNOS阳性神经元的数量明显减少,差异有显著性（P〈0．05）。结论：急性缺氧时锌通过减少海马NoS和nNOS水平而发挥其抗脑缺氧作用。     

中缝背核微量注射L-N-硝基精氨酸甲酯抑制大鼠乙状结肠痛

用Fos免疫组织化学、烟酰胺腺嘌呤二核苷酸磷酸黄递酶(nicotinamide adenine dinucleotide phosphate—di—aphorase,NADPH-d)组织化学及微量注射技术,观察大鼠乙状结肠注射甲醛(5％)诱发的大鼠乙状结肠炎性痛过程中中缝背核一氧化氮合酶(nitric oxide synthase,NOS)神经元的变化,同时观察中缝背核微量注射L-N-硝基精氨酸甲酯(LNAME)对乙状结肠痛的调控作用。结果表明,(1)乙状结肠注射甲醛后,大鼠出现明显的内脏痛反应,中缝背核NOS神经元表达明显增多,中缝背核内出现大量Fos蛋白,在整个中缝背核内均有分布,并且出现Fos／NOS双标神经元,约占中缝背核NOS神经元总数的8％,与生理盐水对照组相比差异有显著性;(2)中缝背核注射L-NAME后,可以明显减少乙状结肠炎性痛大鼠的疼痛学评分及脊髓相应节段Fos蛋白。上述结果提示,中缝背核NOS神经元参与调控大鼠乙状结肠痛,NO在中缝背核促进内脏伤害性信息的传递。     

豚鼠小肠神经节丛的NADPH—黄递酶组织化学观察

目前已知,ＮＡＤＰＨ－－黄递酶组化法可选择性地显示－－氧化氮合成酶（ＮＯｓｙｎｔｈａｓｅ,ＮＯＳ）神经元。因此,我们以ＮＡＤＰＨ－黄递酶组化法,观察了豚鼠小肠肌间神经丛和粘膜下神经丛的神经网格以及ＮＯＳ神经元。结果表明,三段小肠肌间神经丛的神经网眼大小和形态有明显差异,与对应的粘膜下神经丛相比,差异更显著。在肌间神经丛中,ＮＡＤＰＨ－黄递酶阳性神经元胞体大小不等;其长突起伸入节间束,而短突起较多,并可见短突起彼此连接．构成节内偶见的局部神经元回路。从小肠上段到下段,ＮＯＳ神经元数量呈下降趋势。在粘膜下神经丛,我们也观察到少数ＮＯＳ神经元。     

In vivo inhibition of inducible nitric oxide and evaluation of the brain tissue damage induced by Toxocara canis larvae in experimentally infected mice

Nitric oxide (NO) is known to be produced by macrophages, endothelial cells and neurons and synthesized by an enzyme called nitric oxide synthase (NOS). Various effector mechanisms and infections can affect the NO production. Excessive amount of NO will lead to biochemical reactions, which cause toxic effects. In this study the role of NO has been evaluated in larval toxocarosis, which is a systemic parasite infection caused by T. canis larvae. Infection was established in the Balb/c mice with or without inducible NOS (iNOS) inhibition and the effects of infection and NOS inhibition were observed according to the results of SOD and LPx measurements in brain tissue and NADPH-diaphorase (NADP-d) histochemistry. Results of NADPH-d histochemistry indicate that iNOS inhibition has protective effect on the brains of infected mice and that larval T. canis infection could be related to oxidative stress, and NO production and iNOS inhibition can protect the tissue from damage in this infection.     

NADPH-diaphorase, nitric oxide synthase, and tyrosine hydroxylase in the diencephalon of the Rhodeus sericeus (Cyprynidae:Teleostei)

The presence and distribution of nitric oxide synthase (NOS)-like neurons as well as tyrosine hydroxylase-immunoreactive (TH) neurons was studied in the diencephalon of the cypriniform teleost Rhodeus sericeus. The anatomical relationships between tyrosine hydroxylase (TH)- and nitric oxide synthase (NOS)-containing cells were visualized both by NOS-immunohistochemistry and NADPH-histochemistry. Immunohistochemical labeling and morphological studies were performed on the same sections. The results reported in this paper show that both a NOS and TH activity are present in the preoptic region, posterior tuberculum, paraventricular organ and hypothalamus of R. sericeus. Putative nitrergic neurons were identified in all major hypophysiotrophic nuclei of the R. sericeus brain using both NADPH-d histochemistry and nNOS immunohistochemistry. In the preoptic region, nitrergic neurons were found in both the parvocellular and the magnocellular nuclei. Within these nuclei, the distribution of NADPH-d reactivity was similar to that of nNOS immunoreactivity. However, we found no evidence of colocalization of NADPH-d and nNOS in consecutive sections. NOS- and TH-containing neurons were observed in all the nuclei under study (hypothalamus, posterior tuberculum, ventral thalamus) and telencephalon (preoptic region), although most neurons showing the coexistence of both substances were mainly located in the preoptic nucleus and hypothalamus, some labelled neurons were found in the posterior tuberculum. Most of the cerebrospinalliquor-contacting cells (LCNs) in diencephalic periventricular area of R. sericeus were TH-immunoreactive. Also, a large number ofnitrergic small LCNs distributed throughout the third ventricle were observed in these regions. The data obtained supports the existence of a nitrergic circumventricular system in teleost. LCNs in R. sericeus are thought to be involved in osmoregulatory functions as osmosensitive neurons. Due to their chemical properties, NO produced by these cells might play an important role in the maintenance and regulation of CSF homeostasis through the modulation of cerebral blood flow.     

Expression of nitric oxide synthase in mucosal cells of the canine colon

The expression of nitric oxide synthase (NOS) in the mucosa of the canine colon was investigated with in situ hybridzation, immunohistochemistry (using isoform specific antibodies), western analysis, and NADPH diaphorase (NADPH-d) histochemistry. In situ hybridization using a common probe for known isoforms of NOS showed that NOS mRNA was strongly expressed in mucosal cells. A gradient in the degree of hybridization was noted from the base of the crypts to the luminal surface. This gradient was also apparent using an endothelial NOS (eNOS)-specific probe. Neural NOS-like immunoreactivity (nNOS-LI) was observed in columnar epithelial cells, and the same population of cells was stained with NADPH-d. Endothelial NOS-like immunoreactivity (eNOS-LI) was also found in mucosal cells; however, this eNOS-LI was confined to mucous cells. These cells were not stained with NADPH-d. The existence of cNOS in mucosal cells was confirmed by in situ hybridization using the probe which specifically hybridized with mRNA of eNOS and by western blots which demonstrated the expression of a 135-kDa protein in mucosal homogenates. The differential expression of NOS isoforms and the gradient in expression along the length of the crypts suggest complex roles for NO in the development of colonic epithelial cells and in secretion and transport functions of the colonic mucosa.     

Capturing the sublimity of a free radical gas

This paper reviews the work related to nitric oxide (NO) done by the author and his postgraduates and colleagues in the past 7 years in the National University of Singapore. Our work shows that (i) NADPH-d and NO synthase (NOS) are often but not always identical; (ii) NO (as indicated by NADPH-d histochemistry and NOS immunohistochemistry) is generated in some endocrine (thyroid, parathyroid and ultimobranchial glands) and immune (thymus and bursa of Fabricius) organs and the cochlea. It is noted from the above studies that NO could possibly regulate blood flow through the various organs via its presence in the vascular endothelial cells and also via nitrergic neurons innervating the blood vessels. It could also regulate the activity of the secretary cells of these organs by being present in them, as well as acting through nitrergic neurons closely related to them. The paper also examines the Janus-faced nature of NO as a neuroprotective and neurodestructive agent, and the apparent non-involvement of peroxynitrite and inducible NOS in neuronal death occurring in the red nucleus and nucleus dorsalis after spinal cord hemisection.     

Expression and colocalization of NADPH-diaphorase and heme oxygenase-2 in trigeminal ganglion and mesencephalic trigeminal nucleus of the rat

Carbon monoxide (CO) and nitric oxide (NO) are two endogenously produced gases that can function as second messenger molecules in the nervous system. The enzyme systems responsible for CO and NO biosynthesis are heme oxygenase (HO) and nitric oxide synthase (NOS), respectively. The present study was undertaken to examine the distribution of HO-2 and NOS of the trigeminal primary afferent neurons of the rat, located in the trigeminal ganglion (TG) and mesencephalic trigeminal nucleus (MTN), using histochemistry and immunohistochemistry. NADPH-d staining was found in most neurons in TG. The intensely NADPH-d-stained neurons were small- or medium-sized, while the large-sized neurons were less intensely stained. Immunocytochemistry for HO-2 revealed that almost all neurons in TG expressed HO-2, but they did not appear cell size-specific pattern. NADPH-d and HO-2 positive neurons appeared the same pattern, which was NADPH-d activity and HO-2 expression progressively declined from the caudal to rostral part of the MTN. A double staining revealed that the colocalization of NADPH-d/HO-2 neurons was 97.3% in TG and 97.6% in MTN. The remarkable parallels between NADPH-d and HO-2 suggest that NO and CO are likely neurotransmitters and mediate the orofacial nociception and sensory feedback of the masticatory reflex arc together.     

Localization of nitric oxide synthase in rat trigeminal primary afferent neurons using NADPH-diaphorase histochemistry

Summary Nitric oxide (NO) is a ubiquitous gaseous neurotransmitter that has been ascribed to a large number of physiological roles in sensory neurons. It is produced by the enzyme nitric oxide synthase (NOS). To identify the NOS-containing structures of rat trigeminal primary afferent neurons, located in the trigeminal ganglion (TrG) and mesencephalic trigeminal nucleus (MTN), histochemistry to its selective marker nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) was applied in this study. In the TrG approximately half of the neuronal population was NADPH-d reactive. Strongly positive were neurons mainly of small-to-medium size. Neuronal profiles of large diameter were less intensely stained. In addition, NADPH-d-positive nerve fibers were dispersed throughout the ganglion. Nitrergic neurons were located in the caudal part and mesencephalic-pontine junction of the MTN. Most of them were large-sized pseudounipolar cells. In a more rostral aspect, the reactive psedounipolar MTN profiles gradually decreased in number and intensity of staining. There, only a fine meshwork of stained thin fibers and perisomatic terminal arborizations, and also some isolated perikarya of NADPH-d stained multipolar MTN neurons, were observed. The predominant NADPH-d localization in smaller in size TrG neurons, which are considered nociceptive, suggests that NO may play a role in the pain transmission in the rat trigeminal afferent pathways. In addition, the wide distribution of NADPH-d activity in large pseudounipolar and certain multipolar MTN neurons provides substantial evidence that NO may also participate in mediating proprioceptive information from the orofacial region. The differential expression patterns of nitrergic fibers in the TrG and MTN suggest that trigeminal sensory information processing is controlled by nitrergic input through different mechanisms.     

Histochemical methods for detecting nitric oxide synthase

Summary The three isoforms of nitric oxide synthase (NOS), neuronal (nNOS), endothelial (eNOS), and inducible (iNOS), can be visualized in cells and tissues by NADPH-diaphorase (NADPH-d) histochemistry, immunocytochemistry and in situ hybridization. Histochemical demonstration of NADPH-d shows the formazan final reaction product as a solid blue deposit. The ultrastructural localization of NADPH-d in the rat hippocampus showed an electron-dense deposit on membranes predominantly of the endoplasmic reticulum. The immunohistochemical demonstration of nNOS, using the nickel enhancement technique, shows positive reaction product over the dendrites and the soma of the nerve cell in the rat brain. Ultrastructural localization of nNOS in whole mount preparations of myenteric plexus and circular smooth muscle from guinea-pig ileum shows that NOS immunoreactivity was patchily distributed in myenteric neurones and was not specifically associated with any intracellular organelles or with plasma membranes. In situ hybridization, using radio-labelled probes, was used to study nNOS mRNA in lumbar dorsal root ganglia after peripheral transection of the sciatic nerve in rats. Labelling of the NOS mRNA-positive neurones is observed as a series of dense granules over the entire cell. NADPH-d histochemistry, immunocytochemistry and in situ hybridization each have a significant role to play in the localization of NOS. NADPH-d detects an enzyme associated with the NOS molecule, immunocytochemistry detects the NOS molecule, and in situ hybridization detects mRNA for NOS. Therefore, if each of these techniques is applied in carefully controlled experiments, consideration of the accumulated data should be valuable in revealing insights into the biology of NOS.     

Neuronal and endothelial nitric oxide synthase immunoreactivity and NADPH-diaphorase staining in rat and human pancreas: influence of fixation

In this study, we wished to clarify the distribution and co-localization of nitric oxide synthase and NADPH-diaphorase (NADPH-d) in nerve cells, nerve fibres and parenchymal cells in exocrine and endocrine pancreas, and to assess the influence of fixation on the staining pattern obtained. For this purpose, we applied nitric oxide synthase immunocytochemistry and NADPH-d histochemistry to rat and human pancreas under different fixation conditions. Antibodies to neuronal and endothelial nitric oxide synthase were similarly applied. We found complete co-localization of neuronal nitric oxide synthase and NADPH-d in ganglion cells, and in nerve fibres around acini, excretory ducts, blood vessels and in islets of Langerhans of rat and human pancreas. Immunoreactivity for endothelial nitric oxide synthase was co-localized with NADPH-d in endothelial cells. However, in NADPH-d reactive islet and ductal epithelial cells we could detect neither brain nor endothelial nitric oxide synthase immunoreactivity with any fixation protocol applied. There were marked differences in NADPH-d staining of both neurons and parenchymal cells under different fixation conditions. These results indicate the existence of different types of NADPH-d, which are associated or not associated with nitric oxide synthase(s), and which are differently influenced by various fixation procedures in rat and human pancreas.     

NADPH-diaphorase activity in the nociceptive pathways of land snail Megalobulimus abbreviatus: the involvement of pedal ganglia

NADPH-diaphorase (NADPH-d) is a histochemical marker for nitric oxide synthase (NOS), widely used to identify nitric oxide (NO) producing cells in the nervous system of both vertebrates and invertebrates. Using NADPH-d histochemistry and semi-quantitative optical densitometry, we characterized the NO-producing neurons in the pedal ganglia of young and adult Megalobulimus abbreviatus, subjected to aversive thermal stimulus. The animals were killed at different times (3, 6, 12 and 24 h) following stimulus. The enzymatic activity was detected in different cellular subsets and neuronal processes. In all the studied pedal ganglia subregions, the optical density of positive neurons (P < 0.05) and neuropilar area 1 (P < 0.01) was significantly different in treated animals when compared to controls. The increase in nitrergic activity induced by nociceptive stimulus suggests the involvement of NO in the nociceptive circuit of M. abbreviatus, which is well maintained throughout evolution, and could be helpful in drawing cellular homologies with other gastropods.     

Heme oxygenase-2 and nitric oxide synthase immunoreactivity of bovine olfactory receptor neurons and a comparison with the distribution of NADPH-diaphorase staining

It has recently been suggested that, in addition to nitric oxide (NO), carbon monoxide (CO) is an important gaseous messenger which might be involved in vertebrate olfactory transduction because its effects include activation of guanylyl cyclase and the formation of cGMP. As there is no information regarding the presence of heme oxygenase-2 – the constitutive isoform of the heme oxygenase system – in olfactory neurons of non-rodent species, we have investigated the distribution pattern of heme oxygenase-2 in the olfactory epithelium of the bovine, a representative of macrosmatics. Localization of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) activity of the olfactory epithelium was compared with heme oxygenase-2 and NO synthase (NOS) immunoreactivities in order to obtain possible hints at functional significance. NADPH-d activity was particularly intense in apical dendrites of receptor neurons. It was also found in Bowman glands and intraepithelial duct cells. Less intense, discrete NADPH-d activity was present also at intermediate and basal levels of the olfactory epithelium, corresponding to the layer of receptor neuron somata and basal cells. While heme oxygenase-2 activity mainly occured in neuronal perikarya, a very intense NOS immunoreactivity, exclusively for the inducible isoform, was detected in the apical dendrites. Ultrastructurally, NADPH-d histochemistry showed distinct labelling of membranes, in particular of endoplasmic reticulum, mitochondria and nucleus. The coincident localization of the moderate NADPH-d activity and heme oxygenase-2 immunoreactivity in receptor cell perikarya suggest a functional association between NADPH-cytochrome P450 reductase and heme oxygenase-2. In contrast, dendritic localization of NADPH-d activity is topically and possibly functionally related to the presence of the inducible isoform of NOS. The results suggest that both CO and NO may be generated in bovine receptor neurons and thus involved in odorant stimulation. Based on immunocytochemical localization of synthesizing enzymes, NO might be regarded as a direct regulator of transduction related processes while CO might act as a modulator of the initial signal.     

Nitric oxide synthase in mating behavior circuitry of male Syrian hamster brain

Chemosensory and hormonal stimuli are essential for mating in the male Syrian hamster. These signals are processed in a neural circuit that includes the medial amygdaloid nucleus (Me), bed nucleus of the stria terminalis (BNST), and medial preoptic area (MPOA). Nitric oxide is implicated in the regulation of male sexual behavior, and nitric oxide synthase (NOS), the enzyme that catalyzes the production of nitric oxide, is present in the limbic system. In this study, the distribution of NOS-containing neurons in mating behavior circuitry of the male Syrian hamster brain was determined using labeling for brain NOS (bNOS) and reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d). bNOS and NADPH-d labeled equivalent populations of neurons. NOS-containing neurons were clustered in specific subnuclei within the Me, BNST, and MPOA. NOS-positive fibers and neurons were seen in the stria terminalis and ventral amygdalofugal pathway, which link the Me with BNST and MPOA. Many NOS-positive neurons in the posterior subdivision of the Me, the medial preoptic nucleus (MPN), and the ventral premammillary nucleus contain androgen receptors. Castration reduced NOS-positive neurons in the MPN, implying a selective regulation of NOS by gonadal steroids. Together, these results suggest that NOS may contribute to the regulation of male sexual behavior by influencing the central neural processing of hormonal and chemosensory signals in the hamster limbic system. © 1996 John Wiley & Sons, Inc.     

Induction of NADPH diaphorase/nitric oxide synthase in the spinal cord motor neurons of rats following a single and multiple non-penetrative blasts

The present study has demonstrated the induction of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) reactivity and nitric oxide synthase-like immunoreactivity (NOS-LI) in the ventral horn motoneurons of the spinal cord in rats subjected to a single or multiple underground, or a single surface blast. Both enzyme activities were first detected in some motoneurons in laminae VIII and IX of Rexed, 3 hours after the blast. Some NADPH-d and NOS-LI positive neurons were also distributed in laminae VI and VII. The number and intensity of the labelled cells appeared to increase progressively, peaking at 2-3 days after the blast but were drastically reduced thereafter, so that at 7 days after the blast only a few positive neurons were observed. In rats killed at 2 weeks and in longer surviving intervals, i.e. up to 1 month, NADPH-d/NOS reactivity in the ventral horn motor neurons had diminished. The functional significance of the transient expression of neuronal NADPH-d/NOS after the blasts remains uncertain, although from a speculative point of view, the induction of these enzymes probably would reflect an increased production of nitric oxide (NO). In view of the lack of atrophic changes in most, if not all, of motor neurons, it is suggested that the increased levels of NO production after the blast injury may be involved in a neuroprotective function.