C-fos expression in the hypothalamo-pituitary system induced by electroacupuncture or noxious stimulation

Neurogenic Hypotension and Bradycardia Modulated by Electroacupuncture in Hypothalamic Paraventricular Nucleus

Electroacupuncture (EA) stimulates somatic median afferents underlying P5-6 acupoints and modulates parasympathoexcitatory reflex responses through central processing in the brainstem. Although decreases in blood pressure and heart rate by the neural-mediated Bezold-Jarisch reflex responses are modulated by EA through opioid actions in the nucleus tractus solitarius and nucleus ambiguus, the role of the hypothalamus is unclear. The hypothalamic paraventricular nucleus (PVN) is activated by sympathetic afferents and regulates sympathetic outflow and sympathoexcitatory cardiovascular responses. In addition, the PVN is activated by vagal afferents, but little is known about its regulation of cardiopulmonary inhibitory hemodynamic responses. We hypothesized that the PVN participates in the Bezold-Jarisch reflex responses and EA inhibits these cardiopulmonary responses through the PVN opioid system. Rats were anesthetized and ventilated, and their heart rate and blood pressures were monitored. Application of phenylbiguanide every 10 min close to the right atrium induced consistent depressor and bradycardia reflex responses. Unilateral microinjection of the depolarization blockade agent kainic acid or glutamate receptor antagonist kynurenic acid in the PVN reduced these reflex responses. In at least 70% of the rats, 30 min of bilateral EA at P5-6 acupoints reduced the depressor and bradycardia responses for at least 60 min. Blockade of the CCK-1 receptors converted the non-responders into EA-responders. Unilateral PVN-microinjection with naloxone reversed the EA inhibition. Vagal-evoked activity of the PVN cardiovascular neurons was reduced by 30 min EA (P5-6) through opioid receptor activation. These data indicate that PVN processes inhibitory cardiopulmonary reflexes and participates in EA-modulation of the neural-mediated vasodepression and bradycardia.

Separation from a bonded partner alters neural response to inflammatory pain in monogamous rodents

Pain experience is known to be modified by social factors, but the brain mechanisms remain unspecified. We recently established an animal model of social stress-induced hyperalgesia (SSIH) using a socially monogamous rodent, the prairie vole, in which males separated from their female partners (loss males) became anxious and displayed exacerbated inflammatory pain behaviors compared to males with partners (paired males). In the present study, to explore the neural pathways involved in SSIH, a difference in neuronal activation in pain-related brain regions, or "pain matrix", during inflammatory pain between paired and loss males was detected using Fos immunoreactivity (Fos-ir). Males were paired with a female and pair bonding was confirmed in all subjects using a partner preference test. During formalin-induced inflammatory pain, both paired and loss males showed a significant induction of Fos-ir throughout the analyzed pain matrix components compared to basal condition (without injection), and no group differences in immunoreactivity were found among the injected males in many brain regions. However, the loss males had significantly lower Fos-ir following inflammatory pain in the medial prefrontal cortex and nucleus accumbens shell than the paired males, even though base Fos-ir levels were comparable between groups. Notably, both regions with different Fos-ir are major components of the dopamine and oxytocin systems, which play critical roles in both pair bonding and pain regulation. The present results suggest the possibility that pain exacerbation by social stress emerges through alteration of signaling in social brain circuitry.

Early Post-Stroke Electroacupuncture Promotes Motor Function Recovery in Post-Ischemic Rats by Increasing the Blood and Brain Irisin

OBJECTIVE

Recent studies have shown that irisin, a novel peptide hormone derived from muscles, could be used as a potential therapeutic drug against ischemic stroke. Moreover, electroacupuncture (EA) is widely used in the treatment of ischemic stroke. Yet, whether irisin is involved in the EA neuroprotection remains unclear. The following study investigated the association between serum and peri-lesional cortex irisin and EA-induced post-stroke motor recovery in rats.

METHODS

The middle cerebral artery occlusion (MCAO) method was used to induce ischemic stroke in rats. Rats were randomly divided into two groups: a middle cerebral artery occlusion (MCAO) group (MCAO rats without treatment) and an electroacupuncture (EA) group (MCAO rats treated with EA). On the 3rd day post-stroke, infarct volume, behavioral deficits, surviving neurons, irisin protein expression in peri-infarction cortex, muscle tissue, and serum were evaluated to identify the neuroprotective of EA in acute ischemic stroke.

RESULTS

Compared with the MCAO group, the EA group showed better behavioral performance, a smaller cerebral infarct volume, more surviving neurons, and a significant increase in irisin expression in the peri-infarction cortex and serum (p<0.05). However, no difference in irisin expression in the muscle tissue was found between the MCAO group and the EA group (p>0.05).

CONCLUSION

EA promotes motor function recovery, reduces the volume of cerebral infarction, and alleviates neuronal death following ischemic stroke by enhancing the expression of irisin in both the blood and peri-lesional cortex.

Analgesic Neural Circuits Are Activated by Electroacupuncture at Two Sets of Acupoints

To investigate analgesic neural circuits activated by electroacupuncture (EA) at different sets of acupoints in the brain, goats were stimulated by EA at set of Baihui-Santai acupoints or set of Housanli acupoints for 30 min. The pain threshold was measured using the potassium iontophoresis method. The levels of c-Fos were determined with Streptavidin-Biotin Complex immunohistochemistry. The results showed pain threshold induced by EA at set of Baihui-Santai acupoints was 44.74% ± 4.56% higher than that by EA at set of Housanli acupoints (32.64% ± 5.04%). Compared with blank control, EA at two sets of acupoints increased c-Fos expression in the medial septal nucleus (MSN), the arcuate nucleus (ARC), the nucleus amygdala basalis (AB), the lateral habenula nucleus (HL), the ventrolateral periaqueductal grey (vlPAG), the locus coeruleus (LC), the nucleus raphe magnus (NRM), the pituitary gland, and spinal cord dorsal horn (SDH). Compared with EA at set of Housanli points, EA at set of Baihui-Santai points induced increased c-Fos expression in AB but decrease in MSN, the paraventricular nucleus of the hypothalamus, HL, and SDH. It suggests that ARC-PAG-NRM/LC-SDH and the hypothalamus-pituitary may be the common activated neural pathways taking part in EA-induced analgesia at the two sets of acupoints.

The Expression Patterns of c-Fos and c-Jun Induced by Different Frequencies of Electroacupuncture in the Brain

To investigate patterns of c-Fos and c-Jun expression induced by different frequencies of electroacupuncture (EA) in the brain, goats were stimulated by EA of 0, 2, 60, or 100 Hz at a set of "Baihui, Santai, Ergen, and Sanyangluo" points for 30 min. The pain threshold was measured using the potassium iontophoresis method. The levels of c-Fos and c-Jun were determined with Streptavidin-Biotin Complex immunohistochemistry. The results showed that the pain threshold induced by 60 Hz was 82.2% higher (P < 0.01) than that by 0, 2, or 100 Hz (6.5%, 35.2%, or 40.9%). EA induced increased c-Fos and c-Jun expression in most analgesia-related nuclei and areas in the brain. Sixty Hz EA increased more c-Fos or c-Jun expression than 2 Hz or 100 Hz EA in all the measured nuclei and areas except for the nucleus accumbens, the area septalis lateralis, the caudate nucleus, the nucleus amygdala basalis, and the locus coeruleus, in which c-Fos or c-Jun expressions induced by 60 Hz EA did not differ from those by 2 Hz or 100 Hz EA. It was suggested that 60 Hz EA activated more extensive neural circuits in goats, which may contribute to optimal analgesic effects.

A single thalamic target for deep brain stimulation to treat hemi-body pain syndrome

BACKGROUND

Patients experiencing hemi-body pain represent a difficult problem when using the thalamus as a DBS target given its anatomical topology.

METHODS

A 50-year-old HIV positive male underwent a right unilateral thalamic DBS to treat his severe left hemi-body central post-stroke pain following years of unsuccessful medication therapy.

RESULTS

The final active contact of the electrode corresponded to stimulation of the nucleus ventrocaudalis parvocellularis internis, which has provided prolonged pain relief.

CONCLUSION

To our knowledge this was the first time this pattern of pain was treated by a single thalamic DBS electrode, suggesting stimulation in this region may be a feasible target for achieving relief from chronic severe hemi-body pain.

The Possible Neuronal Mechanism of Acupuncture: Morphological Evidence of the Neuronal Connection between Groin A-Shi Point and Uterus

Somatovisceral reflex suggested that the somatic stimulation could affect visceral function like acupuncture which treats diseases by stimulating acupoints. The neuronal connection between somatic point and visceral organ was not clear. Uterine pain referred to the groin region has long been recognized clinically. Wesselmann, using neurogenic plasma extravasation method, showed that uterine pain was referred to the groin region through a neuronal mechanism (Wesselmann and Lai 1997). This connection could be considered through the somatovisceral reflex pathway. However, the relay center of this pathway is still not clearly identified. In the present study, bee venom was injected in the groin region to induce central Fos expression to map the sensory innervation of groin region. Pseudorabies virus (PrV), a transneuronal tracer, was injected in the uterus to identify the higher motor control of the uterus. Immunohistochemistry staining revealed the Fos expression and PrV-infected double-labeled neurons in the nucleus of solitary tract (NTS), the dorsal motor nucleus of vagus (DMX), and the paraventricular hypothalamic nucleus (PVN). These results suggest a somatoparasympathetic neuronal connection (groin-spinal dorsal horn-NTS/DMX-uterus) and a somatosympathetic neuronal connection (groin-spinal dorsal horn-NTS-PVN-uterus). These two neuronal connections could be the prerequisites to the neuronal basis of the somatovisceral reflex and also the neuronal mechanism of acupuncture.

The current use of acupuncture during pregnancy and childbirth

PURPOSE OF REVIEW

Acupuncture has a growing clientele during pregnancy, delivery and the puerperium for an ever increasing list of indications. Objective evidence for its benefit is necessary to establish its roles in current practice.

RECENT FINDINGS

For many of the current uses, randomized studies when conducted using at least one control group have not established any clear advantages from treatment. Those areas which rely upon subjective assessment of symptoms are particularly difficult to investigate without rigorous blinding strategies, separating those who provide the acupuncture from those assessing outcome. Studies investigating the possible therapeutic benefit of acupuncture for managing intrapartum care require outcomes for nulliparae and multiparae to be analysed separately.

SUMMARY

Acupuncture therapy may offer some advantage over conventional treatment in the management of hyperemesis gravidarum and postcaesarean section pain and these areas warrant further study. Rigorous randomized studies, particularly those using objective measures, have failed to identify any obvious benefits from acupuncture for many of the other conditions studied.

A minimal stress model for the assessment of electroacupuncture analgesia in rats under halothane

The use of anesthetics in acupuncture analgesia is controversial. We evaluate a steady-state light anesthesia model to test whether minimal stress manipulation and reliable measurement of analgesia could be simultaneously achieved during electroacupuncture (EA) in animals. A series of experiments were performed. Firstly, EA compliance and tail-flick latencies (TFL) were compared in rats under 0.1%, 0.3%, 0.5%, 0.7%, or 1.1% halothane for 120min. Under 0.5% halothane, TFL were then measured in groups receiving EA at intensity of 3, 10 or 20 volt (V), 1 or 2mg/kg morphine, 20V EA plus naloxone, or control. Subsequently, the effect of EA on formalin-induced hyperalgesia was tested and c-fos expression in the spinal dorsal horn was analyzed. Rats exhibited profound irritable behaviors and highly variable TFL under 0.1% or 0.3% halothane, as well as a time-dependent increase of TFL under 0.7% or 1.1% halothane. TFL remained constant at 0.5% halothane, and needle insertion and electrical stimulation were well tolerated. Under 0.5% halothane, EA increased TFL and suppressed formalin-induced hyperalgesia in an intensity-dependent and naloxone-reversible manner. EA of 20V prolonged TFL by 74%, suppressed formalin-induced hyperalgesia by 32.6% and decreased c-fos expression by 29.7% at the superficial and deep dorsal horn with statistically significant difference. In conclusion, 0.5% halothane provides a steady-state anesthetic level which enables the humane application of EA stimulus with the least interference on analgesic assessment. This condition serves as a minimal stress EA model in animals devoid of stress-induced analgesia while maintaining physiological and biochemical response in the experiment.

Electroacupuncture activates corticotrophin-releasing hormone-containing neurons in the paraventricular nucleus of the hypothalammus to alleviate edema in a rat model of inflammation

BACKGROUND

Studies show that electroacupuncture (EA) has beneficial effects in patients with inflammatory diseases. This study investigated the mechanisms of EA anti-inflammation, using a rat model of complete Freund's adjuvant (CFA)-induced hind paw inflammation and hyperalgesia.

DESIGN

Four experiments were conducted on male Sprague-Dawley rats (n = 6-7/per group). Inflammation was induced by injecting CFA into the plantar surface of one hind paw. Experiment 1 examined whether EA increases plasma adrenocorticotropic hormone (ACTH) levels. Experiments 2 and 3 studied the effects of the ACTH and corticotropin-releasing hormone (CRH) receptor antagonists, ACTH(11-24) and astressin, on the EA anti-edema. Experiment 4 determined whether EA activates CRH neurons in the paraventricular nucleus of the hypothalammus. EA treatment, 10 Hz at 3 mA and 0.1 ms pulse width, was given twice for 20 min each, once immediately post and again 2 hr post-CFA. Plasma ACTH levels, paw thickness, and paw withdrawal latency to a noxious thermal stimulus were measured 2 h and 5 h after the CFA.

RESULTS

EA significantly increased ACTH levels 5 h (2 folds) after CFA compared to sham EA control, but EA alone in naive rats and CFA alone did not induce significant increases in ACTH. ACTH(11-24) and astressin blocked EA anti-edema but not EA anti-hyperalgesia. EA induced phosphorylation of NR1, an essential subunit of the N-methyl-D-aspartic acid (NMDA) receptor, in CRH-containing neurons of the paraventricular nucleus.

CONCLUSION

The data demonstrate that EA activates CRH neurons to significantly increase plasma ACTH levels and suppress edema through CRH and ACTH receptors in a rat model of inflammation.

The role of acupuncture in pain management

This article reviews the theories and applications of acupuncture to musculoskeletal pain management. First, Chinese theories of acupuncture are discussed briefly. Next, current understanding of nociception and central pain modulation is discussed in detail,followed by discussion of the physiologic effect of acupuncture analgesia. Other theories of acupuncture analgesia are presented based on neuromodulation of the central nervous system. Finally,the efficacy of acupuncture for many musculoskeletal pain syndromes,including spine-related pain, soft tissue pain, neuropathic pain, arthritis of the knee, and upper extremity tendinitis, is reviewed. The article concludes with a discussion of methodologic issues related to conducting randomized, placebo-controlled trials of acupuncture and goals for future research in this area of pain management.

c-Fos expression induced by electroacupuncture at the Zusanli point in rats submitted to repeated immobilization

In laboratory animals, acupuncture needs to be performed on either anesthetized or, if unanesthetized, restrained subjects. Both procedures up-regulate c-Fos expression in several areas of the central nervous system, representing therefore a major pitfall for the assessment of c-Fos expression induced by electroacupuncture. Thus, in order to reduce the effect of acute restraint we used a protocol of repeated restraint for the assessment of the brain areas activated by electroacupuncture in adult male Wistar rats weighing 180-230 g. Repeated immobilization protocols (6 days, 1 h/day and 13 days, 2 h/day) were used to reduce the effect of acute immobilization stress on the c-Fos expression induced by electroacupuncture at the Zusanli point (EA36S). Animals submitted to immobilization alone or to electroacupuncture (100 Hz, 2-4 V, faradic wave) in a non-point region were compared to animals submitted to electroacupuncture at EA36S (4 animals/subgroup). c-Fos expression was measured in 41 brain areas by simple counting of cells and the results are reported as number of c-Fos-immunoreactive cells/10,000 m . The protocols of repeated immobilization significantly reduced the immobilization-induced c-Fos expression in most of the brain areas analyzed (P < 0.05). Animals of the EA36S groups had significantly higher levels of c-Fos expression in the dorsal raphe nucleus, locus coeruleus, posterior hypothalamus and central medial nucleus of the thalamus. Furthermore, the repeated immobilization protocols intensified the differences between the effects of 36S and non-point stimulation in the dorsal raphe nucleus (P < 0.05). These data suggest that high levels of stress can interact with and mask the evaluation of specific effects of acupuncture in unanesthetized animals.

Dual effects of acupuncture on gastric motility in conscious rats

The effects of manual acupuncture on gastric motility were investigated in 35 conscious rats implanted with a strain gauge transducer. Twenty (57.1%) rats showed no cyclic groupings of strong contractions (type A), whereas 15 (42.9%) rats showed the phase III-like contractions of the migrating motor complex (type B) in the fasting gastric motility. Acupuncture at the stomach (ST)-36 (Zusanli), but not on the back [Weishu, bladder (BL)-21], increased the peak amplitude of contractions to 172.4 +/- 25.6% of basal in the type A rats (n = 20, P < 0.05). On the other hand, the motility index for 60 min after the acupuncture was not affected by the acupuncture in this group. On the contrary, acupuncture decreased the peak amplitude and motility index to 72.9 +/- 14.0% and 73.6 +/- 16.2% in the type B rats (n = 15, P < 0.05), respectively. The stimulatory and inhibitory effects of acupuncture observed in each type were reproducible on the separate days. In 70% of type A rats, acupuncture induced strong phase III-like contractions lasting for over 3 h that were abolished by atropine, hexamethonium, atropine methyl bromide, and vagotomy. Naloxone significantly shortened the duration of the stimulatory effects from 3.52 +/- 0.21 to 1.02 +/- 0.15 h (n = 3, P < 0.05). These results suggest that acupuncture at ST-36 induces dual effects, either stimulatory or inhibitory, on gastric motility. The stimulatory effects are mediated in part via vagal efferent and opioid pathways.

Analgesia and c-Fos expression in the periaqueductal gray induced by electroacupuncture at the Zusanli point in rats

The need to use anaesthetised or restrained animals in acupuncture research in laboratory animals may represent a confounding variable, since both anaesthesia and stress alter the pain threshold and the activity of pain-related brain areas. In the current study we assessed the participation of the periaqueductal gray (PAG) in electroacupuncture's (EA) analgesic effects applied to the Zusanli point (36S) under carefully controlled stress conditions. Repeated immobilisation protocols (6 days, 1 h/day and 13 days, 2 h/day) were used to diminish the influence of acute immobilisation stress on c-Fos expression and analgesia (tail-flick test) induced by electroacupuncture on the 36S point (EA36S). Animals submitted to immobilisation alone (IMMO) or to electroacupuncture (100 Hz, 2-4 V, faradic wave) on a non-point region (EANP) were compared with animals submitted to electroacupuncture on the 36S point. In animals not previously submitted to repeated immobilisation, electroacupuncture on the 36S point induced analgesia and c-Fos expression in the PAG was not different from that induced by electroacupuncture at a non-acupuncture point. In animals submitted to repeated immobilisation (repeated immobilisation for 6 days or repeated immobilisation for 13 days), however, electroacupuncture on point 36S led to higher levels of analgesia and c-Fos expression, specifically in the ventrolateral PAG (vlPAG), as compared with animal groups subjected only to immobilisation or to electroacupuncture on a non-point. Our findings endorse previous results, and point to a specific part of the PAG involved in the effects of electroacupuncture at the Zusanli point.

Acupuncture modulates expressions of nitric oxide synthase and c-Fos in hippocampus after transient global ischemia in gerbils

The effects of acupuncture on the expressions of nitric oxide synthase (NOS) and c-Fos in the hippocampus of gerbils after transient ischemia were investigated via nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry and Fos immunohistochemistry. In animals of the ischemia-induction groups, both common carotid arteries were occluded for 5 minutes. Animals of the acupunctued groups were given acupunctural treatment at Zusanli twice daily for 9 consecutive days. Acupuncture was shown to decrease NADPH-d and c-Fos levels in both the sham-operation group and the ischemia-induction group. These results suggest that acupuncture modulates the expressions of NOS and c-Fos in the hippocampus.

Hypothalamic effects of millimeter wave irradiation depend on location of exposed acupuncture zones in unanesthetized rabbits

On nine unanesthetized male rabbits, the frequency spectra of hypothalamic electrogram (EEG) were studied during low intensity (10 mW/cm2) millimeter wave (55-75 GHz) exposure to various acupuncture points (zone): auricular, cranial and corporal. The chances of occurrence of significant (p < 0.05) changes in the EEG spectra during irradiation versus, sham experiments were equal to 31, 21 and 5%, respectively. Exposure to auricular zone reduced the EEG power in narrow bands with central frequencies of 5.3, 15.9 Hz and increased ones of 2.6, 3.2, 6.9, 7.9, 11.5 and 25.6 Hz. The main effect of exposure to cranial zone was similar--changes at 15.9 and 25.6 Hz only. The data obtained demonstrate that the responsiveness of the central nervous system to low intensity millimeter wave radiation may depend on the location of the exposed acupuncture zone.

Acupuncture in pain medicine: an integrated approach to the management of refractory pain

As the acupuncture nomenclature permeates medical literature, the artificial barriers to integration of acupuncture and allopathic medicine are disappearing. More patients are looking to their physicians for guidance on how to incorporate acupuncture into their health care, and pain physicians are accepting the challenge. Similar to allopathic medicine, acupuncture is an intricate diagnostic and therapeutic system. However, for practicing physicians, mastery of the skills necessary for safe and effective treatment of many conditions is well within reach. Used in an integrated medical model, acupuncture is well suited to deal with many of the functional problems that allopathic medicine is not equipped to address. The result is patient and physician satisfaction.

cDNA Microarray Analysis of the Differential Gene Expression in the Neuropathic Pain and Electroacupuncture Treatment Models

Partial nerve injury is the main cause of neuropathic pain disorders in humans. Acupuncture has long been used to relieve pain. It is known to relieve pain by controlling the activities of the autonomic nervous system. Although the mechanism of neuropathic pain and analgesic effects of electroacupuncture (EA) have been studied in a rat model system, its detailed mechanism at the molecular level remains unclear. To identify genes that might serve as either markers or explain these distinct biological functions, a cDNA microarray analysis was used to compare the expression of 8,400 genes among three sample groups. Messenger RNAs that were pooled from the spinal nerves of 7 normal, 7 neuropathic pain, and 7 EA treatment rat models were compared. Sixty-eight genes were differentially expressed more than 2-fold in the neuropathic rat model when compared to the normal, and restored to the normal expression level after the EA treatment. These genes are involved in a number of biological processes, including the signal transduction, gene expression, and nociceptive pathways. Confirmation of the differential gene expression was performed by a dotblot analysis. Dot-blotting results showed that the opioid receptor sigma was among those genes. This indicates that opioid-signaling events are involved in neuropathic pain and the analgesic effects of EA. The potential application of these data include the identification and characterization of signaling pathways that are involved in the EA treatment, studies on the role of the opioid receptor in neuropathic pain, and further exploration on the role of selected identified genes in animal models.

Neuropeptide expression in rat paraventricular hypothalamic neurons that project to the spinal cord

The paraventricular hypothalamic nucleus (PVH) exerts many of its regulatory functions through projections to spinal cord neurons that control autonomic and sensory functions. By using in situ hybridization histochemistry in combination with retrograde tract tracing, we analyzed the peptide expression among neurons in the rat PVH that send axons to the spinal cord. Projection neurons were labeled by immunohistochemical detection of retrogradely transported cholera toxin subunit B, and radiolabeled long riboprobes were used to identify neurons containing dynorphin, enkephalin, or oxytocin mRNA. Of the spinally projecting neurons in the PVH, approximately 40% expressed dynorphin mRNA, 40% expressed oxytocin mRNA, and 20% expressed enkephalin mRNA. Taken together with our previous findings on the distribution of vasopressin-expressing neurons in the PVH (Hallbeck and Blomqvist [1999] J. Comp. Neurol. 411:201-211), the results demonstrated that the different PVH subdivisions display distinct peptide expression patterns among the spinal cord-projecting neurons. Thus, the lateral parvocellular subdivision contained large numbers of spinal cord-projecting neurons that express any of the four investigated peptides, whereas the ventral part of the medial parvocellular subdivision displayed a strong preponderance for dynorphin- and vasopressin-expressing cells. The dorsal parvocellular subdivision almost exclusively contained dynorphin- and oxytocin-expressing spinal cord-projecting neurons. This parcellation of the peptide-expressing neurons suggested a functional diversity among the spinal cord-projecting subdivisions of the PVH that provide an anatomic basis for its various and distinct influences on autonomic and sensory processing at the spinal level.

A role for nitric oxide in the median eminence and arcuate nucleus response to capsaicin treatment in rats

This study examined a possible functional involvement of nitric oxide (NO) in the median eminence (ME) and arcuate nucleus (ARC) after capsaicin treatment in rats. Subcutaneous injection of capsaicin increased nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) activity in the ARC-ME compared with vehicle treatment. Fos expression was increased in the ARC after capsaicin injection compared with vehicle-treated rats. Pretreatment with the NO synthase (NOS) inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME) attenuated the effect of capsaicin on Fos expression and NADPH-d reactivity in the ARC-ME in comparison with rats injected with D-NAME, the inactive stereoisomer of L-NAME. These observations suggest that NO makes a major contribution to the response of the ARC-ME to a stressor such as capsaicin.

Electroacupuncture decreases c-fos expression in the spinal cord induced by noxious stimulation of the rat bladder

PURPOSE

The present study investigated the effects of noxious stimulation of the lower urinary tract on neuronal fos protein expression in the spinal micturition center of rats and also examined the effects of electroacupuncture (EA) on fos expression induced by noxious stimulation of the lower urinary tract.

MATERIALS AND METHODS

Experiments were conducted on 21 female Sprague-Dawley rats divided into four groups. Group 1 rats (n = 5) served as normal controls. Group 2 rats (n = 5) received EA at the Sanyinjiao acupoint. Group 3 animals (n = 6) were catheterized through the urethra and instilled with 1% acetic acid, and group 4 (n = 5) animals received EA 1 hour before 1% acetic acid instillation. All animals underwent arterial perfusion, laminectomy, and spinal cord removal. Spinal cords were sectioned and processed for immunohistochemical staining for fos protein.

RESULTS

No fos protein was detected in any spinal neurons in normal control animals, and either none or few (0 to 4 cells/section) fos-immunoreactive (fos-IR) cells were seen in animals treated with EA. Noxious stimulation of the lower urinary tract with 1% acetic acid drastically increased the number of fos-IR neurons (30 to 127 cells/L6 section, mean 76.17+/-13.98; 28 to 77, cells/S1 section, mean 59+/-8.30; 7 to 35 cells/S2 section, mean 19.83+/-4.10). However, EA administered 1 hour before 1% acetic acid instillation significantly decreased the number of fos-IR neurons resulting from chemical irritation (0 to 50 cells/L6 section, mean 19.8+/-9.33; 0 to 47 cells/S1 section, mean 13.2+/-9.12; 0 to 37 cells/S2 section, mean 13.6+/-7.31).

CONCLUSIONS

Our study demonstrates that bladder instillation with 1% acetic acid induces fos protein expression in the spinal micturition center of the rat and that electroacupuncture can reduce this expression. These results suggest a link between electroacupuncture and reduction in spinal neuronal cell activity.

Using c-fos as a neural marker of pain

Just over a decade has past since Hunt et al. reported that the gene c-fos and its protein product Fos are expressed in the spinal cord of rats subjected to peripheral noxious stimulation. These authors showed that noxious stimulation (application of radiant heat or mustard oil) to the hind paw resulted in a massive increase in the expression of Fos in neurons in the dorsal horn of the lumbar spinal cord. Since then, there has been an explosion of studies in which c-fos has been used to study nociception (pain), and the number of such studies increases each year. The net result has been to establish c-fos expression as a valuable tool in pain research. Moreover, recent studies have provided evidence identifying the role of c-fos expression in spinal nociceptive processes. However, there are several important limitations to the practice of using c-fos to study nociception, and these limitations can be easily overlooked as the practice graduates to the status of an established technique. The increasing use of c-fos to study nociception necessitates a critical review of the practice, identifying the shortcomings as well as the strengths of this tool.

Chemical sensory deafferentation abolishes hypothalamic pituitary activation induced by noxious stimulation or electroacupuncture but only decreases that caused by immobilization stress. A c-fos study

We have shown in previous c-fos studies that noxious stimulation or electroacupuncture in deeply anaesthetized rats activate the hypothalamic pituitary corticotrope axis in a specific way. C-fos expression was more pronounced in the arcuate than the paraventricular hypothalamic nuclei, and none occurred in the pituitary intermediate lobe. The absence of the usual autonomic responses to psychological stress, such as tachycardia or blood pressure elevation, suggested a specific action of the somatosensory input on the hypothalamic pituitary axis. To prove this hypothesis, c-fos expression was examined in the paraventricular, arcuate and other hypothalamic nuclei, the pituitary gland, and the A1 and A2 medullary catecholaminergic cell groups of animals deprived of nociceptive primary afferent input by neonatal capsaicin. After noxious stimulation or electroacupuncture, no c-fos enhancement occurred in any of those sites in capsaicin-treated animals, and there was no increased plasma release of adrenocorticotropic hormone. In contrast, the hypothalamic pituitary c-fos activation provoked by immobilization stress though markedly decreased, was not abolished by capsaicin, whereas plasma release of adrenocorticotropic hormone remained undiminished. These findings suggest that noxious stimulation or electroacupuncture act on the hypothalamic pituitary corticotrope axis through an exclusively physical effect depending on the noxious signal elicited in the somatosensory pathway. They also demonstrate the occurrence of a minor somatosensory physical component after forced immobilization, acting on the hypothalamic pituitary axis probably together with the prevalent component of emotional arousal elicited by this form of stress.

Differential expression of c-fos in vitro by all anterior pituitary cell types during the estrous cycle: enhanced expression by luteinizing hormone but not by follicle-stimulating hormone cells

C-fos expression appears in some activated cell types. Because of dynamic changes in gonadotropes during the estrous cycle, this study was initiated to determine if fos might be expressed in gonadotropes before any period of activation. We detected c-fos and pituitary antigens in dissociated anterior pituitary cells by dual-labeling immunocytochemistry. The highest percentage of cells with fos protein were found in proestrous rat populations. In diestrous and proestrous populations, dual labeling showed that 6-9% of pituitary cells contained fos with adrenocorticotropin, thyroid-stimulating hormone, prolactin, or growth hormone antigens. In contrast, only 0.8-3% contained fos with luteinizing hormone (LH) or follicle-stimulating hormone (FSH) antigens. We then tested the hypothesis that gonadotropes might increase fos expression earlier in the cycle. In populations from metestrous rats, c-fos labeling was found in 45% of LH cells compared to only 23% of LH cells in the proestrous group. This suggests that proportionately more LH cells are being activated to produce fos early in the cycle. Perhaps fos is used in translation of LH beta antigens or gonadotropin-releasing hormone (GnRH) receptor mRNAs. In contrast, less than 1% of all pituitary cells expressed fos with FSH at all stages of the cycle (only 6-12% of FSH cells). This differential expression suggests one mechanism behind the regulation of non-parallel storage and release of gonadotropin antigens.

Brain substrates activated by electroacupuncture of different frequencies (I): Comparative study on the expression of oncogene c-fos and genes coding for three opioid peptides

Low and high frequency electroacupuncture (EA)-produced analgesia have been shown to be mediated by different brain substrates and different opioid peptides. In this study, Fos-like immunoreactivity (FLI) and in situ hybridization of the three opioid mRNAs were used to examine the effect of low (2 Hz) and high (100 Hz) frequency EA on neuronal activities, and the expression of opioid genes. 2 Hz and 100 Hz EA induced a markedly different spatial patterns of Fos expression in the rat brain, suggesting there are distinct neuronal pathways underlying EA of different frequencies. Likewise, 2 Hz and 100 Hz EA exert differential effects on opioid gene expression: while 2 Hz EA induced a more extensive and intensive preproenkephalin (PPE) mRNA expression than 100 Hz EA, it had no effect on preprodynorphin (PPD) mRNA expression which was significantly increased by 100 Hz EA stimulation. In contrast, EA of both frequencies did not affect POMC mRNA expression.

Activation of anterior lobe corticotrophs by electroacupuncture or noxious stimulation in the anaesthetized rat, as shown by colocalization of Fos protein with ACTH and beta-endorphin and increased hormone release

A marked expression of the c-fos proto-oncogene has been recently reported in cells of the anterior lobe of the pituitary gland in rats subject to electroacupuncture or noxious thermal stimulation under pentobarbital anaesthesia. The present study was undertaken to identify the activated pituitary cells. Following both kinds of stimulation, most Fos-immunoreactive anterior lobe cells showed colocalization with adrenocorticotropic hormone or beta-endorphin immunoreactivity. No c-fos expression occurred in pituitary cells immunoreactive for growth hormone, prolactin, luteinizing hormone, or thyrotropin-stimulating hormone. A marked rise of adrenocorticotropic hormone and beta-endorphin concentrations occurred in plasma. In the hypothalamus, c-fos expression was increased in the mediobasal nuclei-namely, the arcuate nucleus-and in the paraventricular nucleus, but more in the former. It is suggested that somatosensory noxious input, or the partly noxious input evoked by electroacupuncture, activate the hypothalamo-pituitary-adrenocortical axis as in common forms of stress, but with a specific activation of the mediobasal hypothalamic nuclei and no stimulation of intermediate lobe cells. Opiate release from the pituitary gland may contribute to acupuncture analgesia or the intrinsic antinociceptive reactions triggered by noxious stimulation.