Responses of nitric oxide synthase expression in the gracile nucleus to sciatic nerve injury in young and aged rats

Stimuli-evoked NOergic molecules and neuropeptides at acupuncture points and the gracile nucleus contribute to signal transduction of propagated sensation along the meridian through the dorsal medulla-thalamic pathways

Numerous studies from different international groups have demonstrated that sensations can be propagated along acupuncture channel pathways. The propagated sensation along the channel pathway (PSCP) can be elicited by electroacupuncture (EA), transcutaneous electrical nerve stimulation (TENS), manual acupuncture (MA), and heat applied to distal acupuncture points (acupoints). Nitric oxide (NO) levels were reported to be elevated in the gracile nucleus and skin regions near to the EA sites, with higher levels at acupoints associated with an enhanced expression of NO synthase and transient receptor potential vanilloid type 1. The stimuli, EA, MA, TENS, and heat, have been used to elicit axonal reflexes, which increase local release of NO and neuropeptides such as calcitonin gene related peptide. Furthermore, the sensation of PSCP along the body surface occurs only ipsilaterally to the stimulated acupoints in various human studies, which does not support the involvement of the spinal-thalamic pathway, which would involve cross over transmission of the signals. The gracile nucleus receives ascending input from the sciatic nerve and responds to somatosensory stimulation mainly on the ipsilateral side via the dorsal column pathway. EA at Zusanli (ST36) increases NO release and expression of NO synthase mainly in the ipsilateral side of the gracile nucleus, while the cardiovascular effects and analgesic responses to EA at ST36 are changed by influences of l-arginine-derived NO synthesis in the ipsilateral gracile nucleus in rats. The stimuli-induced release of NOergic molecules and neuropeptides exist high levels in the acupoints, which contain rich neuronal components and blood vessels. Enhanced NOergic molecules at acupoints cause axon reflexes during the stimuli, which elevate cutaneous blood flow. Elevated NOergic molecules and local blood flow may spread over acupoints one after another along the meridian lines differing from nerve pathways following the stimuli to induce PSCP. The same types of stimulation also elicit NO release in the gracile nucleus, which contributes to the somatosensory signal transduction of PSCP through the dorsal medulla-thalamic pathways. Other substances such as serotonin and catecholamines are proposed to mediate responses and certain effects of acupuncture-like stimulation but their mechanisms are poorly-understood. In this review we summarize the current understanding of the neurobiological processes of PSCP research with an emphasis on recent developments of NO mediating stimulation-evoked axon reflexes and somatosensory signal transduction for PSCP perceptions through the dorsal medulla-thalamic pathways. Please cite this article as: Ma SX. Stimuli-evoked NOergic molecules and neuropeptides at acupuncture points and gracile nucleus contribute to signal transduction of propagated sensation along the meridian through the dorsal medulla-thalamic pathways. J Integr Med. 2024; Epub ahead of print.

De novo aging-related NADPH diaphorase positive megaloneurites in the sacral spinal cord of aged dogs

We investigated aging-related changes in nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) in the spinal cord of aged dogs. At all levels of the spinal cord examined, NADPH-d activities were observed in neurons and fibers in the superficial dorsal horn (DH), dorsal gray commissure (DGC) and around the central canal (CC). A significant number of NADPH-d positive macro-diameter fibers, termed megaloneurites, were discovered in the sacral spinal cord (S1-S3) segments of aged dogs. The distribution of megaloneurites was characterized from the dorsal root entry zone (DREZ) into the superficial dorsal horn, along the lateral collateral pathway (LCP) to the region of sacral parasympathetic nucleus (SPN), DGC and around the CC, but not in the cervical, thoracic and lumbar segments. Double staining of NADPH-d histochemistry and immunofluorescence showed that NADPH-d positive megaloneurites co-localized with vasoactive intestinal peptide (VIP) immunoreactivity. We believed that megaloneurites may in part represent visceral afferent projections to the SPN and/or DGC. The NADPH-d megaloneurites in the aged sacral spinal cord indicated some anomalous changes in the neurites, which might account for a disturbance in the aging pathway of the autonomic and sensory nerve in the pelvic visceral organs.

[Effectiveness of Non-Pharmacologic Interventions in Chemotherapy Induced Peripheral Neuropathy: A Systematic Review and Meta-Analysis]

PURPOSE

This study was conducted to evaluate the effectiveness of non-pharmacologic interventions in chemotherapy-induced peripheral neuropathy (CIPN).

METHODS

PubMed, Cochrane Library CENTRAL, EMBASE, CINAHL, and several Korean databases (Until August 2017) were searched. The main search strategy combined terms for peripheral neuropathy and presence of neoplasms. The risk of bias was assessed using the Cochrane's Risk of Bias tool for randomized studies and the Risk of Bias Assessment tool for non-randomized studies. To estimate the effect size, a meta-analysis of the studies was performed using the Rev Man 5.3 program of the Cochrane Library random-effects models were used in the analyses.

RESULTS

Twenty-two studies with a total of 954 participants met the inclusion criteria. Of the 22 studies, 12 were used to estimate the effect size of the non-pharmacologic interventions. The non-pharmacologic interventions used in patients with CIPN were exercise, acupuncture, massage, and foot bath. The acupuncture significantly reduced CIPN symptoms and signs (d=-0.71) and CIPN pain (d=-0.73) (p<.001). Massage and foot bath were also effective in reducing CIPN symptoms (d=-0.68; 95% CI=-1.05, -0.30; p<.001; I²=19%).Exercises were effective in improving muscle strength and endurance(d=-0.55) and quality of life (d=-2.96), but they were not significantly effective in improving CIPN.

CONCLUSION

Although these results provide little evidence of the effectiveness of acupuncture, massage, and foot bath in the treatment of CIPN, they suggest that these interventions can reduce CIPN symptoms in patients with cancer. However, the findings of this study should be interpreted with caution as there is a relative lack of data in this field, and additional well-designed studies are needed. PROSPERO registration: CRD42017076278.

Impaired expression of neuronal nitric oxide synthase in the gracile nucleus is involved in neuropathic changes in Zucker Diabetic Fatty rats with and without 2,5-hexanedione intoxication

These studies examined the influence of 2,5-hexanedione (2,5-HD) intoxication on expression of neuronal nitric oxide synthase (nNOS) in the brainstem nuclei in Zucker Diabetic Fatty (ZDF) vs. lean control (LC) rats. Functional neuropathic changes were also investigated following axonal damage and impaired axonal transport induced by the treatment. Animals were intoxicated by i.p. injection of 2,5-HD plus unilateral administration of 2,5-HD over the sciatic nerve. The mechanical thresholds and withdrawal latencies to heat and cold stimuli on the foot were measured at baseline and after intoxication. The medulla sections were examined by nNOS immunohistochemistry and NADPH-diaphorase histochemistry at the end of the treatments. The mechanical thresholds and withdrawal latencies were significantly decreased while nNOS immunostained neurons and NADPH-diaphorase positive cells were selectively reduced in the gracile nucleus at baseline in ZDF vs. LC rats. NADPH-diaphorase reactivity and nNOS positive neurons were increased in the ipsilateral gracile nucleus in LC rats following 2,5-HD intoxication, but its up-regulation was attenuated in ZDF rats. These results suggest that diabetic and chemical intoxication-induced nNOS expression is selectively reduced in the gracile nucleus in ZDF rats. Impaired axonal damage-induced nNOS expression in the gracile nucleus is involved in neuropathic pathophysiology in type II diabetic rats.

Efficacy of contact needle therapy for chemotherapy-induced peripheral neuropathy

Cancer chemotherapy-induced peripheral neuropathy (CIPN) often results in discontinuation of treatment with potentially useful anticancer drugs and may deteriorate the patient's quality of life. This study investigated the effect of contact needle therapy (CNT) on CIPN caused by responsible chemotherapeutic agents as taxanes and oxaliplatin. Six patients with CIPN were treated with CNT. The severity of CIPN was evaluated using the Common Terminology Criteria for Adverse Events (CTCAE) version 4 and FACT/GOG-Ntx before and after CNT. After the treatment, all of the patients showed some improvement. Four patients showed apparent improvement in breakthrough pain. One of the cases had difficulty in walking because of CIPN in lower extremities, but after 2 times of CNT, he could walk without pain and could continue the chemotherapy. Although its putative mechanisms remain elusive, CNT has strong potential as an adjunctive therapy in CIPN. Well-designed clinical trials with adequate sample size and power are necessary to confirm the findings of this study.

Acupuncture for chemotherapy-induced peripheral neuropathy (CIPN): a pilot study using neurography

OBJECTIVES

Chemotherapy-induced peripheral neuropathy (CIPN) can produce severe neurological deficits and neuropathic pain and is a potential reason for terminating or suspending chemotherapy treatments. Specific and effective curative treatments are lacking.

METHODS

A pilot study was conducted to evaluate the therapeutic effect of acupuncture on CIPN as measured by changes in nerve conduction studies (NCS) in six patients treated with acupuncture for 10 weeks in addition to best medical care and five control patients who received the best medical care but no specific treatment for CIPN.

RESULTS

In five of the six patients treated with acupuncture, NCS improved after treatment. In the control group, three of five patients did not show any difference in NCS, one patient improved and one showed impaired NCS.

CONCLUSION

The data suggest that acupuncture has a positive effect on CIPN. The encouraging results of this pilot study justify a randomised controlled trial of acupuncture in CIPN on the basis of NCS.

Infrared heat treatment reduces food intake and modifies expressions of TRPV3-POMC in the dorsal medulla of obesity prone rats

PURPOSE

Infrared heat, a transient receptor potential vanilloid type-3 (TRPV3) sensitive stimulus, may have potential physiological effects beneficial to treating metabolic syndrome.

MATERIALS AND METHODS

Obesity prone (OP) and obesity resistant (OR) rats were fed for seven days on a high-fat diet. Heat treated OP rats were exposed twice daily to infrared light for 20 min each, separated by 80 min of rest. Food intake, blood pressure, blood glucose, and body weight measurements were taken daily and compared between treated OP rats, untreated OP rats, and OR controls. The animals were perfused with 4% paraformaldehyde, and immunohistochemistry was performed on the coronal brainstem sections with polyclonal antibodies against TRPV3 and pro-opiomelanocortin (POMC). The positive-staining cells in the medulla nuclei were quantified using a microscope with reticule grid.

RESULTS

Food intake, body weight, and mean arterial blood pressure (MAP) were higher in OP rats, a diet-induced metabolic syndrome model, accompanied by a reduced expression of POMC, an anorectic agent, in the hypoglossal nucleus (HN) and medial nucleus tractus solitarius (mNTS). Food intake in heat-treated OP rats was significantly decreased. POMC positive neuron count was increased in the HN and mNTS of OP rats following treatment. TRPV3 positive staining neurons were increased in the HN and mNTS of OP control rats and decreased following the heat treatments.

CONCLUSION

Lowered POMC and heightened TRPV3 expressions in the HN and mNTS are involved in development of hyperphagia and obesity in OP rats. Exposure to infrared heat modifies TRPV3 and POMC expression in the brainstem, reducing food intake.

Nitric oxide implicates c-Fos expression in the cuneate nucleus following electrical stimulation of the transected median nerve

In this study, we investigated whether nitric oxide (NO) modulated injury-induced neuropeptide Y (NPY) releasing and c-Fos expression in the cuneate nucleus (CN) after median nerve transection (MNT). We first examined the temporal changes of neuronal nitric oxide synthase (nNOS) expression in the dorsal root ganglion (DRG) and CN after MNT. Following MNT, the amounts of nNOS-like immunoreactive (nNOS-LI) neurons in the DRG and CN significantly increased as compared with those of the sham-operated rats. Furthermore, 4 weeks after MNT, the increases of nNOS-LI neurons in the DRG and CN were attenuated by pre-emptive lidocaine treatment in a dose-dependent manner. Finally, 4 weeks after MNT, pre-stimulation administration of L-NAME (N (ω)-Nitro-L: -arginine methyl ester) or 7-NI (7-nitroindazole) suppressed the amount of NPY release from the stimulated terminals and thus attenuated c-Fos expression in the CN. Our data implied that NO would modulate neuronal activity in the DRG and CN both after MNT.

Electroacupuncture Zusanli (ST36) on Release of Nitric Oxide in the Gracile Nucleus and Improvement of Sensory Neuropathies in Zucker Diabetic Fatty Rats

The purpose of these studies was to examine the effects of electroacupuncture (EA) Zusanli (ST36) on release of nitric oxide (NO) in the gracile nucleus (GN) and determine if functional neuropathic changes were modified by EA ST36-induced NO in the nucleus in Zucker diabetic fatty (ZDF) rats. The foot withdrawal responses to mechanical, thermal and cold stimuli were measured before and after EA stimulation. A microdialysis probe was implanted in the GN and dialysate samples were collected 20 min before, during and after EA ST36. Total nitrate and nitrite (NO_x⁻) concentrations in the samples were quantified by using chemiluminescence. The baseline dialysate NO_x⁻ concentrations in the GN were decreased in ZDF rats compared to lean control (LC) rats (P < .05). In ZDF rats, dialysate NO_x⁻ releases in the GN were markedly increased during EA ST36, whereas in LC rats, the releases were moderately enhanced at 20–40 min after EA ST36. The withdrawal latencies to mechanical, cold and thermal stimuli were significantly improved 20 min after EA ST36 both in LC and ZDF rats, but not altered by non-acupoint stimulation. The withdrawal latencies to EA ST36 were further potentiated by 3-morpholinyl-sydnoneimine and inhibited by N^G-Propyl-l-arginine infused into the GN in ZDF rats (P < .05). These results show that EA ST36 increases NO release in the GN, and NO in the nucleus modifies withdrawal latencies to mechanical, cold, and thermal nociception stimuli. Data suggest that EA ST36 induces NO release in the GN, which contributes to improvement of sensory neuropathies in rats.

TRPV1 expression in acupuncture points: response to electroacupuncture stimulation

The present study was to examine the distribution of transient receptor potential vanilloid type-1 (TRPV1) receptor immunoreactivity in the acupuncture points (acupoint), and determine the influences of electroacupuncture (EA) stimulation on TRPV1 expression. EA stimulation of BL 40 was conducted in two sessions of 20 min separated by an 80 min interval in anesthetized rats. Sections of skin containing BL 40, and its non-meridian control were examined by immunolabeling with antibodies directed against TRPV1. Without EA, the number of subepidermal nerve fibers expressing TRPV1 was higher in the acupoint than in non-acupoint control skin (p<0.01). The subepidermal nerve fibers showed the co-localization of TRPV1 with peripherine, a marker for the C-fibers and A-δ fibers. The expression of TRPV1 in nerve fibers is significantly increased by EA stimulation in acupoints (p<0.01). However the upregulation in the non acupoint meridian and the non-meridian control skin was short of statistical significance. Double immunostaining of TRPV1 and neuronal nitric oxide synthase (nNOS) revealed their co-localization in both the subepidermal nerve fibers and in the dermal connective tissue cells. These results show that a high expression of TRPV1 endowed with nNOS in subepidermal nerve fibers exists in the acupoints and the expression is increased by EA. We conclude that the higher expression of TRPV1 in the subepidermal nerve fibers and its upregulation after EA stimulation may play a key role in mediating the transduction of EA signals to the CNS, and its expression in the subepidermal connective tissue cells may play a role in conducting the local effect of the EA.

Age-related NADPH-diaphorase positive bodies in the lumbosacral spinal cord of aged rats

In the course of a morphological investigation of age-related changes in the rat spinal cord, using nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry, we found abundant NADPH-d positive bodies, which were characteristically expressed in the aged lumbosacral spinal cord. Together with a normally stained fiber network and a few neurons, the dense, spheroidal NADPH-d positive bodies occurred in portions of the sacral dorsal spinal cords, such as the dorsal commissural nucleus, intermediolateral nuclei, and superficial dorsal horn, and were scattered throughout the dorsal white column. These NADPH-d positive bodies were occasionally observed in a fibrous structure. Two morphologically distinctive subsets of NADPH-d positive bodies were noted in the spinal cord of rats aged 8 to 36 months: 1) highly-dense spheroidal shapes with sharp edges; 2) moderately-dense spheroidal or multiangular shapes with a central "core" and a peripheral "halo". The quantitative analysis, particularly the stereological measurement, confirmed a gradual increase in the incidence and size of NADPH-d positive bodies with increasing age. With nNOS immunohistochemistry, no corresponding structures to NADPH-d positive bodies were detected in aged rats; thus NADPH-d activity is not always specific to the NO-containing neural structures. The major distribution of the NADPH-d positive bodies in the aged lumbosacral spinal cord indicates some anomalous changes in the neurite, which might account for a disturbance in the aging pathway of the autonomic and sensory nerve in the pelvic visceral organs.

Acupuncture treatment improves nerve conduction in peripheral neuropathy

The etiology of peripheral neuropathy (PN) often remains elusive resulting in a lack of objective therapeutic strategies. We conducted a pilot study to evaluate the therapeutic effect of acupuncture on PN as measured by changes in nerve conduction and assessment of subjective symptoms. One hundred and ninety-two consecutive patients with PN as diagnosed by nerve conduction studies (NCS) were evaluated over a period of 1 year. Of 47 patients who met the criteria for PN of undefined etiology, 21 patients received acupuncture therapy according to classical Chinese Medicine as defined by the Heidelberg Model, while 26 patients received the best medical care but no specific treatment for PN. Sixteen patients (76%) in the acupuncture group improved symptomatically and objectively as measured by NCS, while only four patients in the control group (15%) did so. Three patients in the acupuncture group (14%) showed no change and two patients an aggravation (10%), whereas in the control group seven showed no change (27%) and 15 an aggravation (58%). Importantly, subjective improvement was fully correlated with improvement in NCS in both groups. The data suggest that there is a positive effect of acupuncture on PN of undefined etiology as measured by objective parameters.

Involvement of the nitric oxide pathway in synaptic dysfunction following amyloid elevation in Alzheimer's disease

Amyloid-beta (Abeta), a peptide thought to play a crucial role in Alzheimer's disease (AD), has attracted scientific interest with the aim of characterizing the mechanisms by which it is involved in AD pathogenesis. Abeta has been found to markedly impair hippocampal long-term potentiation (LTP), a widely studied cellular model of synaptic plasticity that is thought to underlie learning and memory. The overall purpose of this review is to define the role of the nitric oxide (NO)/cGMP/cAMP-regulatory element binding (CREB) pathway in beta-amyloid-induced changes of basal neurotransmission and synaptic plasticity in the hippocampus, a structure within the temporal lobe of the brain critical for memory storage.

Responses of neuronal nitric oxide synthase expression in the brainstem to electroacupuncture Zusanli (ST 36) in rats

Recent studies have reported that l-arginine-derived nitric oxide (NO) in the gracile nucleus modifies the hypotensive responses to electroacupuncture (EA) stimulation of Zusanli (ST 36). The purpose of this study was to examine the influence of EA stimulation of ST 36 on neuronal NO synthase (nNOS) expression in the brainstem nuclei in rats. EA stimulation of ST 36 and a non-acupoint was performed using 3 Hz of stimulation for 10 s every 2 min for a period of 120 min in rats anesthetized with ketamine. Rats in the sham-treated group received surgery and EA needles were placed into the acupoints without performing the stimulation. After 2-h stimulation and sham treatment, animals were perfused with 4% paraformaldehyde. Sections of rat medulla were examined by immunolabeling with a polyclonal antibody directed against nNOS. The brainstem nuclei were also visualized by NADPH-diaphorase histochemistry, a marker of nNOS activity. nNOS expression and NADPH-diaphorase reactivity were quantified by using a microscope with reticule grid to count the number of positive cells over a nucleus. Unilateral EA stimulation of ST 36 in rats caused increases in nNOS immunostained cells in the rostral region of the ipsilateral gracile nucleus, but was not altered in the contralateral gracile nucleus compared with sham-treated rats (P < 0.05, n = 6-7). NADPH-diaphorase-positive cells were also increased in the ipsilateral gracile nucleus of rats with EA stimulation. nNOS immunostaining and NADPH-diaphorase-positive neurons were significantly increased in both ipsilateral and contralateral sides of the medial nucleus tractus solitarius (mNTS) in rats receiving EA ST 36 compared with sham-treated animals (P < 0.05). nNOS immunostaining and NADPH-diaphorase reactivity was neither altered in the gracile nucleus and mNTS of non-acupoint stimulated rats nor other brainstem nuclei in rats with EA ST 36. These results show that nNOS immunoreactivity and NADPH-diaphorase reactivity are consistently increased in the gracile nucleus and the mNTS by EA ST 36. We conclude that EA ST 36 induces nNOS expression in the gracile nucleus and mNTS, and enhanced nNOS-NO in the nuclei may modify central cardiovascular regulation, which contribute to hypotensive effects of acupuncture.

Neurobiology of Acupuncture: Toward CAM

It has long been accepted that acupuncture, puncturing and scraping needles at certain points on the body, can have analgesic and anesthetic effects, as well as therapeutic effects in the treatment of various diseases. This therapy, including acupuncture anesthesia, has drawn the attention of many investigators and become a research subject of international interest around the world. Numerous studies have demonstrated that the nervous system, neurotransmitters, endogenous substances and Jingluo (meridians) may respond to needling stimulation and electrical acupuncture. An abundance of information has now accumulated concerning the neurobiological mechanisms of acupuncture, in relation to both neural pathways and neurotransmitters/hormonal factors that mediate autonomic regulation, pain relief and other therapeutics. Early studies demonstrated that the analgesic effects of electroacupuncture (EA) are mediated by opioid peptides in the periaqueductal gray. Recent evidence shows that nitric oxide plays an important role in mediating the cardiovascular responses to EA stimulation through the gracile nucleus-thalamic pathway. Other substances, including serotonin, catecholamines, inorganic chemicals and amino acids such as glutamate and alpha-aminobutyric acid (GABA), are proposed to mediate certain cardiovascular and analgesic effects of acupuncture, but at present their role is poorly understood. The increased interest in acupuncture health care has led to an ever-growing number of investigators pursuing research in the processes of the sense of needling touch, transduction of needling stimulation signals, stimulation parameters and placebos. In this Review, the evidence and understanding of the neurobiological processes of acupuncture research have been summarized with an emphasis on recent developments of nitric oxide mediating acupuncture signals through the dorsal medulla-thalamic pathways.

Enhanced nitric oxide concentrations and expression of nitric oxide synthase in acupuncture points/meridians

OBJECTIVES

The objectives of this study were to examine the distributions of nitric oxide (NO) in the skin points (acupoints)/meridian regions and determine whether neuronal nitric oxide synthase (nNOS) protein levels were associated with NO concentrations in the areas.

DESIGN

Low skin resistance points (LSRP) on the skin surface in response to electrical stimuli were performed in anesthetized adult rats. The skin together with subcutaneous tissue was isolated in meridian regions from PC 2 to 6, BL 36 to 57, CV 3 to 22, and GV 2 to 14. Control skin tissues were obtained in the areas close to related meridians without containing LSRP. Concentrations of nitrite (NO(2)(-)), nitrate (NO(3)(-)), and total NO(2)(-) plus NO(3)(-) (NO(x)(-)) were quantified in the skin tissues, micropunches of brain nuclei, and blood vessels in a blinded fashion. Western blots were also conducted using polyclonal anti-nNOS and anti-endothelial nitric oxide synthase (eNOS) antibody in the skin tissues.

RESULTS

NO(x)(-) and NO(3)(-) concentrations were higher (45 +/- 8% and 43 +/- 7% in the CV, 47 +/- 7% and 51 +/- 9% in the BL, and 47 +/- 8% and 45 +/- 6% in the PC) than those in control regions (p < 0.05, n = 6). NO(x)(-) concentrations are 2- to 3-fold greater in skin tissues than those in brain regions and blood vessels (p < 0.05, n = 6-8). nNOS protein levels were consistently increased in the skin regions of BL, PC, and GV meridians compared with their controls (p < 0.05, n = 5-7) but endothelial NO synthase expression was not changed.

CONCLUSION

This is the first evidence showing that NO contents and nNOS expression are consistently higher in the skin acupoints/meridians associated with low electric resistance. The results suggest that enhanced NO in the acupoints/meridians is generated from multiple resources including neuronal NOergic system, and NO might be associated with acupoint/meridian functions including low electric resistance.

Reversal of biochemical and behavioral parameters of brain aging by melatonin and acetyl L-carnitine

The potential utility of dietary supplementation in order to prevent some of the oxidative and inflammatory changes occurring in the brain with age, has been studied. The cerebral cortex of 27-month-old male B6C3F1 mice had elevated levels of nitric oxide synthase 1 (EC 1.14.13.39) (nNOS) and peptide nitrotyrosine relative to cortices of younger (4-month-old) animals. After 25-month-old mice received basal diet together with 300 mg/l acetyl L-carnitine in the drinking water for 8 weeks, these levels were fully restored to those found in younger animals. A partial restoration was found when old animals received basal diet supplemented with 200 ppm melatonin in the diet. Levels of mRNA (messenger RNA) for nNOS were unchanged following these treatments implying translational regulation of nNOS activity. Behavioral indices indicative of exploratory behavior were also depressed in aged animals. Dietary supplementation with melatonin or acetyl L-carnitine partially reversed these changes. These findings suggest that dietary supplementation cannot merely arrest but indeed reverse some age-related increases in markers of oxidative and inflammatory events occurring with the cortex.

Nitric oxide synthase in the frog cerebellum: response of Purkinje neurons to unilateral eighth nerve transection

When vestibular damage occurs, nitric oxide synthase (NOS) expression in rat cerebellar flocculus is affected. Since compensation for postural symptoms occurs and Purkinje cells play an important role in movement coordination and motor learning, we analyzed in situ the induction of NOS in the Purkinje cell population of the cerebellum (corpus cerebelli) of frog after unilateral transection of the eighth statoacoustic nerve to gain insight into the role of NO in neural plasticity after injury. Three days after neurectomy, the early effects induced NADPH diaphorase reactivity in most of the Purkinje cells on the ipsilateral side, while on the contralateral side the highest labeling was observed at 15 days. This finding can give information on the dynamics of vestibular compensation, in which NOS involvement was investigated. At 30 days, NADPH diaphorase reactivity was present in a large number of Purkinje cells of the whole cerebellum, while at 60 days a down-regulation for NADPH diaphorase reactivity was evident. A similar trend was observed for NOS-immunoreactivity, which was still present at 60 days in a high percentage of Purkinje cells, mainly on the ipsilateral side. On the basis of cell density evaluations, it was proposed that the early induction of NOS after neurectomy was linked to the degeneration of a part of the Purkinje neurons, while the permanence of NOS labeling might be due to a neuroprotective role of NO in the restoration phase of the vestibular compensation process.

Plastic changes and nitric oxide synthase induction in neurons which innervate the regenerated tail of the lizard Gekko gecko. II. The response of dorsal root ganglion cells to tail amputation and regeneration

The lizard tail regenerates after amputation, which severs the spinal cord and spinal nerves. Dorsal root ganglia (DRGs) do not regenerate in the regrowing tail, which is innervated by DRGs rostral to the amputation. With Nissl staining, NADPH-diaphorase histochemistry and nitric oxide synthase (NOS) immunohistochemistry, we investigated NOS expression and its relationship with structural changes in DRG neurons of caudotomized lizards. First, by horseradish peroxidase retrograde tracing we here provided evidence that the sensory innervation of the regenerated tail derives only from the three pairs of DRGs rostral to the amputation plane. These ganglia were then analyzed in control animals with original intact tail, at 5, 15 and 30 days after caudotomy, and at 8 months in lizards with mature regenerates. Caudotomy elicited in DRG neurons marked hypertrophy that persisted after tail regeneration. In control ganglia, most neurons were lightly NADPH-diaphorase-positive, a few were unstained or intensely stained. Tail transection elicited marked staining up-regulation, and an increase in the proportion of intensely positive neurons. The staining intensity peaked in DRG neurons at 15 days and was still significantly increased in respect to controls several months after complete tail regeneration. NOS immunoreactivity in DRGs matched the histochemical findings. NADPH-diaphorase positivity was also enhanced in the dorsal horn superficial laminae of the corresponding spinal segments. We demonstrate that transection of the lizard spinal nerves, provoked by tail loss, elicits in the axotomized primary sensory neurons marked NOS enhancement, which accompanies axon elongation in the regrowing tail and persists after the end of this process.