Alterations in endogenous brain beta-endorphin release by adrenal medullary transplants in the spinal cord

Reducing adsorption to improve recovery and in vivo detection of neuropeptides by microdialysis with LC-MS

Neuropeptides are an important class of neurochemicals; however, measuring their concentration in vivo by using microdialysis sampling is challenging due to their low concentration and the small samples generated. Capillary liquid chromatography with mass spectrometry (cLC-MS) can yield attomole limits of detection (LOD); however, low recovery and loss of sample to adsorptive surfaces can still hinder detection of neuropeptides. We have evaluated recovery during sampling and transfer to the cLC column for a selection of 10 neuropeptides. Adding acetonitrile to sample eliminated carryover and improved LOD by 1.4- to 60-fold. The amount of acetonitrile required was found to have an optimal value that correlated with peptide molecular weight and retention time on a reversed phase LC column. Treating AN69 dialysis membrane, which bears negative charge due to incorporated sulfonate groups, with polyethylenimine (PEI) improved recovery by 1.2- to 80-fold. The effect appeared to be due to reducing electrostatic interaction between peptides and the microdialysis probe because modification increased recovery only for peptides that carried net positive charge. The combined effects improved LOD of the entire method by 1.3- to 800-fold for the different peptides. We conclude that peptides with both charged and hydrophobic regions require combined strategies to prevent adsorption and yield the best possible detection. The method was demonstrated by determining orexin A, orexin B, and a novel isoform of rat β-endorphin in the arcuate nucleus. Dialysate concentrations were below 10 pM for these peptides. A standard addition study on dialysates revealed that while some peptides can be accurately quantified, some are affected by the matrix.

Cortisol and antidepressant effects of yoga

CONTEXT

Hypercortisolemia is well-known in depression and yoga has been demonstrated earlier to reduce the parameters of stress, including cortisol levels.

AIM

We aimed to find the role of yoga as an antidepressant as well as its action on lowering the serum cortisol levels.

SETTINGS AND DESIGN

An open-labeled study consisting of three groups (yoga alone, yoga along with antidepressant medication and antidepressant medication alone) was conducted at a tertiary care psychiatry hospital.

METHODOLOGY

Out-patient depressives who were not suicidal were offered yoga as a possible antidepressant therapy. A validated yoga module was used as therapy taught over a month and to be practiced at home daily. Patients were free to choose the drugs if their psychiatrist advised. Patients (n=54) were rated on Hamilton Depression Rating Scale (HDRS) with serum cortisol measurements at baseline and after 3 months. In 54 patients, assessments and blood test results were both available. 19 each received yoga alone or with drugs and 16 received drugs only. Healthy comparison subjects (n=18) too underwent morning cortisol measurements once.

RESULTS

Serum cortisol was higher in depressives compared with controls. In the total sample, the cortisol level dropped significantly at the end of treatment. More patients in the yoga groups had a drop in cortisol levels as compared to drug-only group. In the yoga-only group, the cortisol drop correlated with the drop in HDRS score (antidepressant effect).

CONCLUSION

The findings support that yoga may act at the level of the hypothalamus by its 'anti-stress' effects (reducing the cortisol), to bring about relief in depression.

Volume transmission of beta-endorphin via the cerebrospinal fluid; a review

There is increasing evidence that non-synaptic communication by volume transmission in the flowing CSF plays an important role in neural mechanisms, especially for extending the duration of behavioral effects. In the present review, we explore the mechanisms involved in the behavioral and physiological effects of β-endorphin (β-END), especially those involving the cerebrospinal fluid (CSF), as a message transport system to reach distant brain areas. The major source of β-END are the pro-opio-melano-cortin (POMC) neurons, located in the arcuate hypothalamic nucleus (ARH), bordering the 3^rd ventricle. In addition, numerous varicose β-END-immunoreactive fibers are situated close to the ventricular surfaces. In the present paper we surveyed the evidence that volume transmission via the CSF can be considered as an option for messages to reach remote brain areas. Some of the points discussed in the present review are: release mechanisms of β-END, independence of peripheral versus central levels, central β-END migration over considerable distances, behavioral effects of β-END depend on location of ventricular administration, and abundance of mu and delta opioid receptors in the periventricular regions of the brain.

Intrathecal grafting of porcine chromaffin cells reduces formalin-evoked c-Fos expression in the rat spinal cord

Chromaffin cells from the adrenal gland secrete a combination of neuroactive compounds including catecholamines, opioid peptides, and growth factors that have strong analgesic effects, especially when administered intrathecally. Preclinical studies of intrathecal implantation with xenogeneic bovine chromaffin cells in rats have provided conflicting data with regard to analgesic effects, and recent concern over risk of prion transmission has precluded their use in human clinical trials. We previously developed a new, safer source of adult adrenal chromaffin cells of porcine origin and demonstrated an in vivo antinociceptive effect in the formalin test, a rodent model of tonic pain. The goal of the present study was to confirm porcine chromaffin cell analgesic effects at the molecular level by evaluating neural activity as reflected by spinal cord c-Fos protein expression. To this end, the expression of c-Fos in response to intraplantar formalin injection was evaluated in animals following intrathecal grafting of 10(6) porcine or bovine chromaffin cells. For the two species, adrenal chromaffin cells significantly reduced the tonic phases of the formalin response. Similarly, c-Fos-like immunoreactive neurons were markedly reduced in the dorsal horns of animals that had received injections of xenogeneic chromaffin cells. This reduction was observed in both the superficial (I-II) and deep (V-VI) lamina of the dorsal horn. The present study demonstrates that both xenogeneic porcine and bovine chromaffin cells transplanted into the spinal subarachnoid space of the rat can suppress formalin-evoked c-Fos expression equally, in parallel with suppression of nociceptive behaviors in the tonic phase of the test. These findings confirm previous reports that adrenal chromaffin cells may produce antinociception by inhibiting activation of nociceptive neurons in the spinal dorsal horn. Taken together these results support the concept that porcine chromaffin cells may offer an alternative xenogeneic cell source for transplants delivering pain-reducing neuroactive substances.

NMDA antagonist peptide supplementation enhances pain alleviation by adrenal medullary transplants

Spinal transplantation of adrenal medullary chromaffin cells has been shown to decrease pain responses in several animal models. Improved potency may be possible by engineering cells to produce greater levels of naturally derived analgesics. As an initial screen for potential candidates, adrenal medullary transplants were evaluated in combination with exogenously administered neuropeptides in rodent pain models. Histogranin is a 15-amino acid peptide that exhibits NMDA receptor antagonist activity. The stable derivative [Ser1]histogranin (SHG) can attenuate pain symptoms in some animal models. The formalin model for neurogenic inflammatory pain and the chronic constriction injury (CCI) model for neuropathic pain were used to evaluate the combined effects of chromaffin cell transplantation and intrathecal (IT) SHG injections. Animals were implanted with either adrenal medullary or control striated muscle tissue in the spinal subarachnoid space. For evaluation of formalin responses, animals were pretreated with SHG (0.5, 1.0, 3.0 microg) followed by an intraplantar injection of formalin, and flinching responses were quantified. Pretreatment with SHG had no significant effect on flinching behavior in control animals at lower doses, with incomplete attenuation only at the highest dose. In contrast, 0.5 microg SHG significantly reduced flinching responses in animals with adrenal medullary transplants, and 1.0 microg nearly completely eliminated flinching in these animals in the tonic phase. For evaluation of effects on neuropathic pain, animals received transplants 1 week following CCI, and were tested for thermal and mechanical hyperalgesia and cold allodynia before and following SHG treatment. The addition of low doses of SHG nearly completely eliminated neuropathic pain symptoms in adrenal medullary transplanted animals, while in control transplanted animals only thermal hyperalgesia was attenuated, at the highest dose of SHG. These results suggest that SHG can augment adrenal medullary transplants, and the combination may result in improved effectiveness and range in the treatment of chronic pain syndromes.

The neural basis of the complex mental task of meditation: neurotransmitter and neurochemical considerations

Meditation is a complex mental process involving changes in cognition, sensory perception, affect, hormones, and autonomic activity. Meditation has also become widely used in psychological and medical practices for stress management as well as a variety of physical and mental disorders. However, until now, there has been limited understanding of the overall biological mechanism of these practices in terms of the effects in both the brain and body. We have previously described a rudimentary neuropsychological model to explain the brain mechanisms underlying meditative experiences. This paper provides a substantial development by integrating neurotransmitter systems and the results of recent brain imaging advances into the model. The following is a review and synthesis of the current literature regarding the various neurophysiological mechanisms and neurochemical substrates that underlie the complex processes of meditation. It is hoped that this model will provide hypotheses for future biological and clinical studies of meditation.

No detectable analgesic effects in the formalin test even with one million bovine adrenal chromaffin cells

The present experiments were conducted to identify analgesic agents for transfection into immortalized adrenal chromaffin cell lines to maximize their analgesic potential. Analgesic agents known to be produced by adrenal chromaffin cells were infused intrathecally at a low dose (0.2 microg) which might conceivably be attained by adrenal chromaffin cell transplants. Numerous agents, administered individually and in two-factor combinations, produced significant analgesic effects in the formalin test. Before assessing the potential additive or synergistic effects of these analgesic agents with adrenal chromaffin cells, studies were conducted to demonstrate analgesic effects with adrenal chromaffin cells alone. Analgesic effects were previously reported in the literature with 80-100k intrathecal bovine adrenal chromaffin (BAC) cells; but in the present study 500k purified BAC cells failed to produce detectable analgesic effects. One million purified BAC cells also failed to produce analgesic effects in the formalin test. In a final study, even nicotine-stimulated release from one million purified BAC cells failed to produce analgesic effects in the formalin test. The fact that even one million nicotine-stimulated BAC cells failed to demonstrate therapeutic potential in these blinded experiments under conditions which were clearly sensitive to the analgesic agents produced by BAC cells, raises serious questions about the clinical utility of this experimental treatment.

Adrenal medullary transplants reduce formalin-evoked c-fos expression in the rat spinal cord

Previous studies have indicated that adrenal medullary chromaffin cells transplanted into the spinal subarachnoid space can alleviate pain behaviors in several animal models. The goal of this study was to assess whether decreased activation of spinal dorsal horn neurons responsive to nociceptive stimuli may contribute to these antinociceptive effects. In order to address this, expression of neural activity marker c-fos in response to intraplantar formalin was evaluated in animals with intrathecal adrenal medullary or control striated muscle transplants. Adrenal medullary transplants significantly attenuated formalin-induced flinching behaviors in both acute and tonic phases of the formalin response, in comparison with control transplanted animals. Fos-like-immunoreactive (Fos-LI) cell numbers were markedly reduced in the dorsal horns of animals with adrenal medullary transplants in comparison to robust Fos-LI expression in control transplanted animals. This reduction was observed in both superficial and deep laminae of the dorsal horn, but the magnitude of the decrease was greatest in lamina V. Similar to reports using other antinociceptive treatments, some residual c-fos expression was observed, particularly in laminae I-II, in animals with adrenal medullary transplants. The results of these studies suggest that adrenal medullary transplants produce antinociception in part by inhibiting spinal dorsal horn neuronal activation in response to noxious stimuli.

Impaired release of beta-endorphin in response to serotonin in a rat model of depression

Involvement of both the serotonergic and the endogenous opioid systems in the onset of depressive behavior has been suggested. Previously we showed that serotonin (5-hydroxytryptamine) facilitates beta-endorphin release in the nucleus accumbens (NAcc). Herein, the microdialysis method was used to assess in vivo the effects of serotonin on beta-endorphin release in a rat model of depressive behavior (the Flinders sensitive line, FSL), before and after antidepressant treatment. The basal extracellular level of beta-endorphin in the NAcc of FSL rats did not differ significantly from that in control rats. However, serotonin-induced beta-endorphin release was impaired in FSL rats. Chronic treatment (18 days) with desipramine or paroxetine did not significantly affect the extracellular levels of beta-endorphin in the NAcc of either the FSL or control rats. However, the chronic antidepressant treatment did normalize the serotonin-induced release of beta-endorphin in FSL rats, as well as their behavioral manifestation of depressive behavior. Our results show that depressive behavior may relate to an impaired effect of serotonin on beta-endorphin release in the NAcc in a rat model of depression, and suggest a possible new mode of action of antidepressant drugs.