CSF and plasma levels of pro-opiomelanocortin-related peptides in reversible ischaemic attacks and strokes

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.

Beta-endorphin and cortisol levels in plasma and CSF following acute experimental spinal traumas

beta-endorphin and cortisol were measured in cerebrospinal fluid (CSF) and plasma by radioimmunological method (RIA) in two groups of rabbits with spinal cord traumatic injuries at cervical and lumbar levels, respectively with and without concomitant spinal shock and arterial hypotension, and in a group of sham operated animals as controls. The two groups with spinal lesions displayed a significant beta-endorphin increase in CSF, whereas the cortisol level remained unchanged both in the spinal traumatized rabbits and in controls. Both the opioid and the cortisol concentration rose significantly in plasma in all three groups and in particular resulted significantly higher in the cervical traumatized group where spinal trauma was associated with spinal shock and hypotension. However, no significant difference was found when beta-endorphin concentrations in plasma were compared between the sham operated animals and the spinal lumbar traumatized animals without concomitant spinal shock. The results seem to suggest that the beta-endorphin increase in CSF is related to the nervous tissue lesion, while its increase in plasma, like that of cortisol, is due to surgery or other stress factors inherent in the experiment. This independent behaviour of beta-endorphin in plasma and in CSF suggests its different origin in these two compartments.

Concentration of enkephalins in cerebrospinal fluid of patients after severe head injury

We studied head-injured patients treated at the Department of Neurosurgery, Silesian University School of Medicine, Katowice. The patients underwent lumbar puncture on days 1, 4 and 7 for diagnostic reasons. The levels of leu-enkephalin (LENK) and met-enkephalin (MENK) were examined in 4.5 ml of cerebrospinal fluid (CSF). The control group included patients with lumbar discopathy from whom CSF fluid was collected during myelography. Enkephalins were extracted by column chromatography and their levels were assayed radioimmunologically. The results indicate that enkephalins may play a certain role in the pathophysiological response of nervous tissue to traumatic injury. Constantly elevated MENK levels together with decreasing LENK levels in patients with a Glasgow coma scale score < or = 8 may be useful as a poor prognostic factor. It is also suggested that LENK and MENK play different pathophysiological roles.

The effects of naloxone on retinal ischemia in rats

The efficacy of naloxone (NL), a broad spectrum opioid antagonist, on retinal ischemia, was evaluated in a rat model of retinal ischemia with histopathologic and morphometric criteria. Two intraperitoneal injections of naloxone 3 mg/kg given immediately and 6 hr after reperfusion showed beneficial effects to the retina as evaluated at 2, 7, and 14 days after reperfusion. Morphologically, the naloxone-treated group showed better-preserved ganglion cells, nerve fiber layer, and inner nuclear layer. Morphometrically, in the treated groups, inner retinal thickness at all three time points and ganglion cell counts at 7 days showed higher values than vehicle controls. This beneficial effect of naloxone was dose-dependent with a minimal effective total dose of 6 mg/kg. A possible role of opiate receptors in retinal ischemia is suggested.

Evidence of alpha-N-acetyl beta-endorphin in human cerebrospinal fluid

Alpha-N-acetyl-beta-endorphin (Ac-beta-EP) is a post-translational product of beta-endorphin (beta-EP) with no analgesic properties. Ac beta-EP is present in human fetal and adult pituitary gland and cross-reacts in all available beta-EP assays. This study evaluates levels of Ac-beta-EP in the cerebrospinal fluid (CSF) of 22 normal subjects and 15 chronic headache sufferers. Since dopamine may play a role in the acetylation process, homovanillic acid levels were also determined. After extraction and high performance liquid chromatographic (HPLC) fractionation of CSF, an immunoreactive Ac-beta-EP peak was detected coeluting with reference peptide. Ac-beta-EP was detectable in all but 5 normal subjects. In headache sufferers, Ac-beta-EP levels were always detectable and their mean value was significantly higher than that of healthy subjects (11.6 +/- 11.8 vs 3.9 +/- 3.6 fmol/ml; P less than 0.01). Conversely, CSF beta-endorphin (beta-EP) concentrations were decreased in headache patients (9.8 +/- 9.4 vs 15.7 +/- 9.7 fmol/ml; P less than 0.05), and as a consequence the beta-EP/Ac-beta-EP ratio was also markedly reduced (P less than 0.005). No difference was observed for CSF homovanillic acid concentrations. These data demonstrate that HPLC coupled to radioimmunoassay allows the identification of low but significant amounts of Ac beta-EP in human CSF. This compound represents a confounding factor when beta-EP immunoreactivity is assessed by conventional methods. In headache sufferers, Ac-beta-EP levels were higher than normal, whereas beta-EP concentrations were lower.(ABSTRACT TRUNCATED AT 250 WORDS)

A double blind randomized pilot trial of naloxone in the treatment of acute ischemic stroke

Attention has focused on naloxone, an opiate receptor antagonist, because of its potential benefit in reversing neurological damage after acute cerebral ischemia. To evaluate the safety and possible efficacy of high-dose naloxone in ischemic stroke patients we planned a double blind pilot study. Between January 1989 and May 1990 24 patients were randomly assigned to the naloxone or placebo group according to age and neurological deficit. Naloxone was given in a loading dose of 5 mg/kg over 10 minutes followed by a 24-hour infusion at the rate of 3.5 mg/kg/h. 10 patients experienced minor side effects but none of them had to discontinue the treatment. 9 patients improved: 6 in the naloxone group and 3 in the placebo group, but no significant difference was found using the non parametric Mann-Whitney test. Our study suggests that naloxone is safe at the dose used, but the results do not support the planning of similar trials on a larger scale.

Cerebrospinal fluid beta-endorphin in Rett syndrome

An hypothesis of increased endorphinergic activity has been proposed to account for the characteristic symptoms of Rett syndrome. Cerebrospinal fluid samples from eight girls with Rett syndrome were analysed for beta-endorphin (beta-EP) immunoactivity and compared with samples from a control group of 15 children with acute leukaemia in remission. Severity of symptoms was not found to be related to beta-EP level. A group of early-treated adolescents with phenylketonuria had beta-EP levels similar to the Rett syndrome patients, but no symptoms resembling theirs. Therefore it is unlikely that increased levels of beta-EP are of primary pathogenetic significance. The conflicting findings of many earlier reports may be a result of differences between control groups.

CSF beta-endorphin, HVA and 5-HIAA of dementia of the Alzheimer type and Binswanger's disease in the elderly

Cerebrospinal fluid (CSF) concentration of beta-endorphin (beta-Ep), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) was measured in 15 patients with dementia of the Alzheimer type (DAT) and in 16 patients suspected of having Binswanger's disease (BD) by MRI, which sometimes resembles DAT clinically. These were classified into three stages according to severity of dementia, Stage 1 (mild dementia)-Stage 3 (severe dementia). CSF levels of HVA decreased significantly in severe dementia, but the level of 5-HIAA did not correlate with dementia severity in both dementia groups. beta-Ep levels did not differ significantly between any stages of DAT, and among controls. beta-Ep levels, however, in BD Stage 1 (27.5 +/- 5.9 pg/ml) were significantly higher (p less than 0.05), but level in Stage 3 (6.7 +/- 2.0) was significantly lower (p less than 0.001) than in the controls (19.2 +/- 4.5). These results suggest that CSF beta-Ep may depend on the cause of dementia rather than severity of dementia, and could possibly distinguish the closely resembling BD from true DAT.

The effects of naloxone on cerebral blood flow and cerebral function during relative cerebral ischemia

CBF and somatosensory evoked potentials (SEPs) were measured in a model of moderate cerebral ischemia in anesthetized spontaneously hypertensive rats. The rats were bled to reduce SEP amplitudes to about 50% of prebleeding control. The consequent blood pressure fall reduced CBF to 77% of control as measured by the laser-Doppler technique. Naloxone (5 mg kg-1 i.v. plus 25 mg kg-1 h-1 i.v. for 30 min) caused a significant increase in SEP amplitudes, while CBF did not change significantly. In addition, the latency of the first SEP component decreased toward prebleeding values. Heart rate (HR) decreased, but MABP was held constant by a pressure-regulating reservoir. In unbled rats, naloxone (5 mg kg-1 i.v.) caused a transient small increase in MABP and SEP amplitudes and decrease in HR. These results indicate that sensory input is regulated by opioid systems. Increased opioid activity may inhibit ascending sensory pathways during relative cerebral ischemia and thereby depress SEP responses. Thus, naloxone can release this inhibition and enhances SEP independently of CBF during relative cerebral ischemia. Similar mechanisms might explain the apparently beneficial effects of naloxone in some stroke models.

Reduced cerebrospinal fluid B-endorphin levels in Rett syndrome

Cerebrospinal fluid (CSF) levels of B-endorphin (B-EP), B-lipotropin (B-LPH) and ACTH were measured in nine girls with Rett syndrome with features of autistic behavior (3.7-12.1 years of age) and in ten children with chronic leukemia (control group). The peptides were measured by radioimmunoassay, either directly in the sample (ACTH) or after Sephadex G-75 column chromatography, in order to eliminate interfering substances (B-LPH and B-EP). The CSF B-EP patient levels (20.8 +/- 13.1 fmol/ml, means +/- SD) were significantly lower than in age-matched controls (69.1 +/- 32.6, P less than 0.01), whereas the B-LPH and ACTH levels were in the control range. No correlations were found between the clinical findings and CSF neuropeptide concentrations. These data demonstrate a decrease in central opiate activity in girls with Rett syndrome.