Partial colocalization of NADPH-diaphorase and acetylcholinesterase positivity in spinal cord neurons

The freely diffusible radical, nitric oxide (NO), has been assumed to act as a retrograde signaling molecule that modulates transmitter release. Acetylcholine (ACh) is known to function as a typical neurotransmitter. In the present work we have examined the presence of both transmitters (NO and ACh) and their possible relations in the rabbit spinal cord. In our experiments we have used histochemical methods for the visualization of acetylcholinesterase (AChE) and NADPH diaphorase (NADPH-d) which label neurons that express nitric oxide synthase (NOS). Both histochemical methods were performed separately or together on the same sections of the thoracic spinal cord. NADPH-d positive dark blue stained neurons were seen mostly in superficial and deep layers of the dorsal horn, preganglionic autonomic neurons and pericentral area. The presence of AChE positive amber yellow neurons was confirmed mostly in motoneurons located in the ventral horns and in neurons of the pericentral and intermediate zone. Besides the above mentioned neurons, also double-labeled neurons were found which contained both the yellow and dark blue histochemical product. Their presence was confirmed in the intermediate zone and in the pericentral area. Thus, the co-existence of NADPH-d and AChE occurred in the location of interneurons. Our observations suggest that NO may play a role in the control of cholinergic neuronal activity and that NO can be involved in the modulation of synaptic transmission.     

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.     

Postnatal development of nitrergic and cholinergic structures in rat spinal cord

Nitric oxide (NO) is known to be a freely diffusible gaseous neurotransmitter that is not requiring synaptic connection to exert its effects. Nitric oxide synthase (NOS), the enzyme responsible for NO synthesis can be visualised by nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry. Other neurotransmitter is a classical neurotransmitter acetylcholine (ACh), regulated by enzyme acetylcholinesterase (AChE) that hydrolyses the acetylcholine after its releasing. This work is presenting results of histochemical study of the NADPH-d and AChE expression (nitrergic and cholinergic neurons) in the spinal cord (SC) during various periods in its development. Specimens from Wistar rat pups in the age ranging from 1st to 21st postnatal days (P1-P21) have been compared with those of adult rats (P90). Transverse sections of the SC were evaluated by light microscope. In adults, the NADPH-d positivity was detectable in the neurons of superficial and deep layers of the dorsal horn, pericentral area and in the area of preganglionic autonomic nuclei. AChE positive structures were seen in the same locations as previous ones with the exception of two locations: in superficial layers of the dorsal horn AChE staining was absent, while in the ventral horn the groups of AChE positive motoneurons were found. At the perinatal period both NADPH-d and AChE positive neurons were stained from slight to moderate intensity only. During later developmental periods the staining gradually increased and achieved adult level of intensity on the day P21. Our results confirmed the presence of nitrergic and cholinergic neurons in investigated areas of the SC and indicated their fully functioning of NADPH-d and AChE positive structures in SC from the third postnatal week.     

Fluorocitrate,an Inhibitor of Glial Metabolism,Inhibits the Up-Regulation of NOS Expression,Activity and NO Production in the Spinal Cord Induced by Formalin Test in Rats

Previous experiments have suggested that nitric oxide plays an important role in nociceptive transmission in the spinal cord. In order to explore the involvement of glia in the NO-mediated nociceptive transmission, the present study was undertaken to investigate the effect of fluorocitrate (FC), an inhibitor of glial metabolism, on NOS expression and activity and NO production in the spinal cord during the process of peripheral inflammatory pain and hyperalgesia induced by formalin test in rats. Sixty adult male Sprague–Dawley rats were randomly assigned into sham, formalin, formalin + normal saline (NS), and formalin + FC groups. The NOS expression, NOS activity and NO production was detected by NADPH-d histochemistry staining, NOS and NO assay kit, respectively. It was found that formalin test significantly up-regulated NOS expression and activity and NO production in the laminae I–II of the dorsal horn and the grey matter around the central canal in the lumbar spinal cord at 1 h after the formalin test. Selective inhibition of glia metabolism with intrathecal administration of FC (1 nmol) significantly inhibited the up-regulation in NOS expression and activity and NO production normally induced by the formalin test, which was represented with decreases in the number and density of the NADPH-d positive cells in the dorsal horn and grey matter around the central canal, and decrease in density of NADPH-d positive neuropil in the dorsal horn in formalin + FC group compared with formalin group. The results suggested that glia may be involved in the NO-mediated nociceptive transmission in the spinal cord. X.-C. Sun, W.-N. Chen and S.-Q. Li contributed equally to this work.     

CGRP受体拮抗剂CGRP8-37对甲醛炎性痛大鼠自发痛反应及脊髓后角NOS表达和NO含量的影响

目的:探讨CGRP受体拮抗剂CGRP8-37对甲醛炎性痛大鼠自发痛反应及脊髓后角NOS表达和NO含量的影响.方法:大鼠足底注射甲醛制造炎性痛模型;计数缩足反射次数反映自发痛程度;NADPH-d组织化学法观察脊髓后角NOS表达;硝酸还原酶法测定NO-3/NO-2含量以反映NO含量.结果:足底注射甲醛后,动物出现自发痛反应行为.足底注射甲醛后24 h,双侧脊髓后角NOS表达及NO含量明显增加.预先鞘内注射CGRP8-37可使甲醛诱导的自发性缩足反射次数明显减少,并可明显抑制甲醛炎性痛诱导的脊髓后角NOS表达及NO含量的增加.结论:甲醛炎性痛时,脊髓后角CGRP受体激活可促进NOS活性表达及NO的产生.     

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.     

Spatiotemporal Alterations of the NO/NOS Neuronal Pools Following Transient Abdominal Aorta Occlusion: Morphological and Biochemical Studies in the Rabbit

1. Brief interruption of spinal cord blood flow resulting from transient abdominal aortic occlusion may lead to degeneration of specific spinal cord neurons and to irreversible loss of neurological function. The alteration of nitric oxide/nitric oxide synthase (NO/NOS) pool occurring after ischemic insult may play a protective or destructive role in neuronal survival of affected spinal cord segments.2. In the present study, the spatiotemporal changes of NOS following transient ischemia were evaluated by investigating neuronal NOS immunoreactivity (nNOS-IR), reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry, and calcium-dependent NOS (cNOS) conversion of [³H] l-arginine to [³H] l-citrulline.3. The greatest levels of these enzymes and activities were detected in the dorsal horn, which appeared to be most resistant to ischemia. In that area, the first significant increase in NADPHd staining and cNOS catalytic activity was found immediately after a 15-min ischemic insult.4. Increases in the ventral horn were observed later (i.e., after a 24-h reperfusion period). While the most intense increase in nNOS-IR was detected in surviving motoneurons of animals with a shorter ischemic insult (13 min), the greatest increase of cNOS catalytic activity and NADPHd staining of the endothelial cells was found after stronger insult (15 min).5. Given that the highest levels of nNOS, NADPHd, and cNOS were found in the ischemia-resistant dorsal horn, and nNOS-IR in surviving motoneurons, it is possible that NO production may play a neuroprotective role in ischemic/reperfusion injury.     

MK—801降低炎性痛在鼠脊髓NOS表达和NO含量

用NADPH-d组织化学法,观察鞘内注射NMDA受体拮抗剂MK-801对大鼠右后掌皮下注射甲醛诱发的炎症性痛及痛过敏过程中脊髓后角一氧化氮合酶(NOS)表达的影响,同时测定一氧化氮(NO)代谢终产物     

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.     

Neuronal nitric oxide synthase in the rabbit spinal cord visualised by histochemical NADPH-diaphorase and immunohistochemical NOS methods

The NADPH-diaphorase (NADPH-d) staining method is widely used in the investigation of both the central and peripheral nervous systems. Neuronal nitric oxide synthase (nNOS) has previously been shown to be responsible for the NADPH-d activity in neurons. However, NADPH-d activity does not always fully represent the enzyme nNOS. We investigated the distribution of NADPH-d activity and nNOS protein in the rabbit spinal cord for all groups of neurons and Rexed's laminae. In most laminae the distribution of NADPH-d activity was identical to nNOS immunoreactivity. Both were present in the dorsal horn and in pericentral areas of the spinal cord, but some differences existed. The superficial part of the dorsal horn (laminae I-III) stained more intensely for NADPH-d than for nNOS. However, the most prominent difference was seen in the lateral part of the dorsal horn--the lateral collateral pathway (LCP). The LCP stained strongly for NADPH-d activity, while nNOS staining was absent. Although there is an excellent correlation between NADPH-d staining and nNOS immunohistochemical staining in the spinal cord in general, the presence of staining differences necessitates the use of immunohistochemistry for some specialized applications.     

Cauda equina syndrome and nitric oxide synthase immunoreactivity in the spinal cord of the dog

The development of the cauda equina syndrome in the dog and the involvement of spinal nitric oxide synthase immunoreactivity (NOS-IR) and catalytic nitric oxide synthase (cNOS) activity were studied in a pain model caused by multiple cauda equina constrictions. Increased NOS-IR was found two days post-constriction in neurons of the deep dorsal horn and in large, mostly bipolar neurons located in the internal basal nucleus of Cajal seen along the medial border of the dorsal horn. Concomitantly, NOS-IR was detected in small neurons close to the medioventral border of the ventral horn. High NOS-IR appeared in a dense sacral vascular body close to the Lissauer tract in S1-S3 segments. Somatic and fiber-like NOS-IR appeared at five days post-constriction in the Lissauer tract and in the lateral and medial collateral pathways arising from the Lissauer tract. Both pathways were accompanied by a dense punctate NOS immunopositive staining. Simultaneously, the internal basal nucleus of Cajal and neuropil of this nucleus exhibited high NOS-IR. A significant decrease in the number of small NOS immunoreactive somata was noted in laminae I-II of L6-S2 segments at five days post-constriction while, at the same time, the number of NOS immunoreactive neurons located in laminae VIII and IX was significantly increased. Moreover, high immunopositivity in the sacral vascular body persisted along with a highly expressed NOS-IR staining of vessels supplying the dorsal sacral gray commissure and dorsal horn in S1-S3 segments. cNOS activity, based on a radioassay of compartmentalized gray and white matter regions of lower lumbar segments and non-compartmentalized gray and white matter of S1-S3 segments, proved to be highly variable for both post-constriction periods.     

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.     

Age-related changes in nitric oxide synthase in the lateral geniculate nucleus of rats

Age-related changes in nitric oxide production in the visual system have not been well characterized. Therefore, we used staining and image-processing approaches to describe changes in levels of neuronal nitric oxide synthase (nNOS), the NADPH-diaphorase (NADPH-d) histochemical marker, and 3-nitrotyrosine in the lateral geniculate nucleus (LGN) of young and aged rats. The LGN plays an important role in the visual system, as it acts as a visual relay nucleus. Quantitative analysis of NADPH-d-positive and nNOS-immunoreactive neurons revealed significant optical density increases in the dorsal LGN and ventral LGN of aged rats; however, no significant changes were observed in the number of neurons with age. 3-Nitrotyrosine immunoreactivity was increased in the dorsal LGN and ventral LGN of aged rats. These results indicate that increased nitric oxide production and peroxynitrite may be associated with alterations in visual function during aging.     

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.     

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。     

Differential localization of neuronal nitric oxide synthase immunoreactivity and NADPH-diaphorase activity in the cat spinal cord

The distributions of neuronal nitric oxide synthase immunoreactivity (NOS-IR) and NADPH-diaphorase (NADPH-d) activity were compared in the cat spinal cord. NOS-IR in neurons around the central canal, in superficial laminae (I and II) of the dorsal horn, in the dorsal commissure, and in fibers in the superficial dorsal horn was observed at all levels of the spinal cord. In these regions, NOS-IR paralleled NADPH-d activity. The sympathetic autonomic nucleus in the rostral lumbar and thoracic segments exhibited prominent NOS-IR and NADPH-d activity, whereas the parasympathetic nucleus in the sacral segments did not exhibit NOS-IR or NADPH-d activity. Within the region of the sympathetic autonomic nucleus, fewer NOS-IR cells were identified compared with NADPH-d cells. The most prominent NADPH-d activity in the sacral segments occurred in fibers within and extending from Lissauer's tract in laminae I and V along the lateral edge of the dorsal horn to the region of the sacral parasympathetic nucleus. These afferent projections did not exhibit NOS-IR; however, NOS-IR and NADPH-d activity were demonstrated in dorsal root ganglion cells (L7-S2). The results of this study demonstrate that NADPH-d activity is not always a specific histochemical marker for NO-containing neural structures.     

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.     

NO nerves in trematodes, too! NADPH-diaphorase activity in adult Fasciolopsis buski

The free radical nitric oxide (NO) is a unique molecule with an avidity to react with other molecules and is known to function as a neuronal messenger. This nitrergic transmitter with diverse functions in signal transduction, being a gas, is not stored in synaptic vesicles but is generated in various neuronal cells by a family of nitric oxide synthases (NOSs). The NADPH-d histochemical reaction is regarded as a selective marker for NOS in the neuronal tissue. With histochemical detection of NADPH-d, the presence of NOS is demonstrated in the digenetic trematode, Fasciolopsis buski. Strong NADPH-d staining was observed in the neuronal cell bodies in the two cerebral ganglia, the brain commissure and the nerve fibers in the main nerve cords. NADPH-d staining was also detectable in the innervation of the pharynx, the cirrus sac and the ventral sucker besides being observable sporadically in the nerve tributaries in the general parenchyma. NO released by the whole worm kept in PBS at 37 degrees C could also be measured biochemically. The NOS activity was assayed in the whole worm homogenate and also in the tissue homogenate containing only the anterior pre-acetabular part of the parasite body. The presence of NOS in this digenean parasite confirms that a nitrergic innervation occurs in the trematode group also as in other groups of exclusively parasitic helminths and that NO represents an old signal molecule in evolutionary scale.     

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.     

The vulnerability of nitrergic neurons to transient spinal cord ischemia: a quantitative immunohistochemical and histochemical study

Spinal cord ischemia belongs to serious and relatively frequent diseases of CNS. The aim of the present study was to find out the vulnerability of nitrergic neurons to 15 min transient spinal cord ischemia followed by 1 and 2 weeks of reperfusion. We studied neuronal nitric oxide synthase (nNOS) and nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) in structural elements of lumbosacral spinal cord along its rostrocaudal axis. In addition, a neurological deficit of experimental animals was evaluated. Spinal cord ischemia, performed on the rabbit, was induced by abdominal aorta occlusion using Fogarty catheter introduced into the right femoral artery for a period of 15 min. After surgical intervention the animals survived for 7 and 14 days. nNOS-immunoreactivity (nNOS-IR) was measured by immunohistochemical and NADPHd-positivity by histochemical method, and both immunohistochemical and histochemical stainings were quantified by densitometric analyses. Neurological deficit was evaluated according Zivin′s criteria. The number of nNOS-IR and/or NADPH-d positive neurons and the density of neuropil were markedly increased in superficial dorsal horn (laminae I–III) after 15 min ischemia and 7 days of reperfusion. However, ischemia followed by longer time of survival (14 days) returned the number of nNOS-IR and NADPH-d positive neurons to control. In the pericentral region (lamina X) containing interneurons and crossing fibers of spinal tracts, than in lamina VII and in dorsomedial part of the ventral horn (lamina VIII) we recorded a decreased number of nNOS-IR and NADPH-d positive neurons after both ischemia/reperfusion periods. In the medial portion of lamina VII and dorsomedial part of the ventral horn (lamina VIII) we observed many necrotic loci. This area was the most sensitive to ischemia/reperfusion injury. Fifteen minute ischemia caused a marked deterioration of neurological function of hind limbs, often developing into paraplegia. A quantitative immunohistochemical and histochemical study have shown a strong vulnerability of nitrergic neurons in intermediate zone to transient spinal cord ischemia.