Lack of analgesic effect of opioids on neuropathic and idiopathic forms of pain

The aim of the present study has been to assess the responsiveness of various types of chronic pain to opioids given i.v. and tested against placebo in a double-blind, randomized fashion. Pain classified as primary nociceptive was effectively alleviated (P greater than 0.001) while neuropathic deafferentation pain was not significantly influenced by morphine or equivalent doses of other opioids. Also 'idiopathic' pain, defined as chronic pain with no or little demonstrable pathology, failed to respond. The results were not related to whether the patients were regular users of narcotic analgesics or not. The outcome of our double-blind opioid test has proved useful to justify a continued, or discontinued, use of narcotic medication in individual patients. It may also support the indication and choice of invasive stimulation procedures (spinal cord or brain). The results of the study illustrate the misconception of chronic pain as an entity and highlight the importance of recognizing different neurobiological mechanisms and differences in responsiveness to analgesic drugs as well as to non-pharmacological modes of treatment. The opioid test has thus become a valuable tool in pain analysis and helpful as a guide for further treatment.

Improvement of schizophrenic patients treated with [des-Tyr1]-gamma-endorphin (DTgammaE)

It was postulated from animal experiments that gamma-endorphin and, in particular, the nonopiate-like peptide [des-Tyr1]-gamma-endorphin (DTgammaE, beta-lipotropin [beta-LPH]62-77) have neurolepic-like activity. To test this, 14 patients with long-lasting, relapsing schizophrenic or schizoaffective psychosis resistant to conventional neuroleptics were treated with DTgammaE. An open design was used first for six patients (study 1) and a double-blind, crossover design for the other eight (study 2). In study 1, all neuroleptic medication was discontinued and 1 mg of DTgammaE zinc phosphate was given daily intramuscularly for about seven days. In study 2, six patients were maintained with neuroleptic therapy and two patients were drug free; all eight received daily intramuscular injections of 1 mg of nonlasting DTgammaE in saline and solution for eight days. There was transient or semipermanent improvement in both studies in which the psychotic symptoms diminished or even disappeared. In study 2, there was a slight but significant improvement with the first treatment. Improvement continued and by day 4, the psychotic symptoms had almost disappeared. No toxic side effects were noted. These effects of DTgammaE may be a consequence of the normalization of beta-endorphin homeostasis in the brain.

Profound analgesic effects of beta-endorphin in man

Profound and long-lasting analgesia (mean duration of pain relief 33.4 h, range 22.5--73.5 h) was produced by intrathecal administration of 3 mg synthetic beta-endorphin in all of 14 patients with intractable pain due to disseminated cancer. No respiratory depression, hypotension, hypothermia, or catatonia was observed.

Endorphins in psychiatry: an overview and a hypothesis

This article presents an overview of the biochemistry, pharmacology, and physiology of endogenous opioid peptides (endorphins). Clinical psychopharmacology of exogenous opiate agonists and antagonists is reviewed. The evidence presented in the review is compatible with a hypothesis that the level of functional endorphins may be related to psychological events, with a normal level needed for psychological homeostasis. One corollary of this hypothesis is that the level of opioids in the brains of the mentally ill may be disturbed. Therapeutic implications of this hypothesis are considered.

Reduction of distress vocalization in chicks by opiate-like peptides

All the opiate-like peptides we tested (Met-enkephalin, (D-Ala2)-Met-enkephalin-NH2, beta-endorphin, (D-Ala2)-beta-endorphin, (D-Ala2)-alpha-endorphin, (D-Ala2)-gamma-endorphin) were capable of reducing distress vocalizations (DV's) in socially-isolated chicks when injected into the vicinity of the fourth ventricle in doses as low as 100 picomoles. All of these substances were at least as potent as equimolar doses of morphine sulfate. In general, DV's were a more sensitive measure of opiate-like peptide effects than reductions in body temperature. In a more limited study using peripheral injections, it was determined that (D-Ala2)-Met-enkephalin at doses of 400 nanomoles/kg, like morphine sulfate, was more effective in reducing DV's, than an equimolar dose of beta-endorphin. beta-endorphin was not as effective via a peripheral route as it was via central administration.

beta-Endorphin. Intravenous infusion causes behavioral change in psychiatric inpatients

Ten depressed and eight schizophrenic patients received synthetic human beta-endorphin infusions in a double-blind, placebo-controlled, crossover design. Physicians' and nurses' ratings and patients' self-ratings were used to measure behavioral change. Depressed patients improved significantly two to four hours after beta-endorphin treatment when compared with placebo treatment. There was no significant change in the schizophrenic patients as a group, although six of eight worsened after beta-endorphin treatment. No significant behavioral effects were observed during the infusions themselves or on postinfusion days.

beta-Endorphin and schizophrenia

To study the effects of beta-endorphin in chronic schizophrenia, nine male patients participated in a double-blind crossover comparison of a single intravenous 20-mg injection of beta-endorphin and saline. Bolus injection of beta-endorphin from an albumin-coated syringe produced markedly higher plasma concentrations than did slow intravenous infusion from a non-albumin-coated syringe. Beta-endorphin intravenously injected in nine patients produced a statistically significant increase in serum prolactin levels. In one patient, both 10 mg of morphine sulfate and 20 mg of beta-endorphin produced similar increases in the alpha power of the EEG. In eight patients, beta-endorphin administration was associated with a statistically significant but not clinically obvious improvement in schizophrenic symptoms.

Vascular effects, angiotensin I-converting enzyme (ACE)-inhibitory activity, and antihypertensive properties of peptides derived from egg white

In this study, we have identified novel antihypertensive peptides derived from egg-white proteins. The sequences YRGGLEPINF and ESIINF produced an acute blood-pressure-lowering effect in spontaneously hypertensive rats upon a single oral administration. Our results suggest that the antihypertensive action could be attributed to a vascular-relaxing mechanism that would occur in vivo independently of angiotensin I-converting enzyme (ACE) inhibition, because neither these peptides nor their main digestion fragments, except for the dipeptide YR, acted as ACE inhibitors in vitro. The vasodilator and antihypertensive activity of the sequences ESI and NF would explain the blood-pressure-lowering effect of ESIINF. With regard to YRGGLEPINF, in addition to NF, YR appeared as the main fragment responsible for its activity. The dipeptide YR, named kyotorphin and previously identified as an endogenous analgesic neuropeptide in the central nervous system, showed strong vasodilator and antihypertensive properties. The structure-activity features of the vasodilator peptides are discussed.

The effect of centrally administered neuropeptides on the development of stress-induced gastric ulcers in rats

Neurotensin (NT) and bombesin, which are heterogeneously distributed in both brain and gastrointestinal tissue of several mammalian species, inhibit the formation of stress-induced gastric ulcers in rats. Many other endogeneous neuropeptides have also been reported to be present in brain and gastrointestinal tissue. The present study was conducted to evaluate the effect of some of these peptides on the development of cold-restraint stress (CRS)-induced gastric ulcers in rats. In addition, the effect of thyrotropin-releasing hormone (TRH), which antagonizes many of the CNS effects of NT, was investigated to determine whether this tripeptide antagonizes the cytoprotective effect of NT in this CRS model. All peptides were initially administered intracisternally (ic) in doses equimolar to 30 micrograms NT. As previously reported, NT (30 micrograms, ic) completely prevented the development of gastric ulcers in rats exposed to three hours of CRS. Bombesin, beta-endorphin, substance P, and somatostatin also exhibited cytoprotective activity. Several other peptides studied in the CRS model exerted no significant effects on the development of gastric ulcers; these included cholecystokinin octapeptide, gastrin, leu-enkephalin, met-enkephalin, and bradykinin. Two peptides, vasoactive intestinal polypeptide and TRH, significantly increased the severity of gastric ulcerations. The cytoprotective effect of NT was dose dependent. In contrast, lower doses of beta-endorphin, substance P, and somatostatin were cytoprotective whereas higher doses were not. Finally, concomitant ic injections of TRH antagonized the cytoprotective effects of NT and bombesin, but not that of beta-endorphin. The present results suggest that certain brain peptides may participate in modulating the gastric mucosal barrier, thereby increasing or decreasing its vulnerability to stress-induced lesions.

Endorphins, dopamine, and schizophrenia

The theory that alterations of dopaminergic synaptic transmission may play a role in the pathogenesis of schizophrenia is widely accepted. A more recent theory links the endorphin system to the etiology of schizophrenia. We propose that these two theories may be combined into a single model. Recent neurochemical and pharmacological findings have indicated close functional relationships between the endorphin and dopamine systems. Endorphins modulate dopaminergic synaptic transmission by exerting both presynaptic and postsynaptic effects. On the molecular level, this modulation may involve the activity of nucleotide cyclases and protein phosphorylation systems. Thus, the dopaminergic neuronal hyperactivity, currently believed to be related to schizophrenia, may be caused by a primary alteration in the endorphin system. Several hypotheses about the nature of that alteration have been advanced and tested in therapeutic experiments with schizophrenic patients. These experiments have not yet yielded definitive results.

Suppression of withdrawal symptoms by dynorphin in heroin addicts

The effectiveness of dynorphin-(1-13) in suppressing heroin withdrawal was studied. At a dose of 60 micrograms/kg body weight, dynorphin-(1-13) was effective in suppressing withdrawal symptoms. When saline was administered a strong placebo effect was noticed that, however, did not influence the outcome of the results. Only three out of the twelve patients receiving dynorphin-(1-13) experienced some mild side-effects such as feeling warm, dizziness and precordial formication.

beta-Endorphin in obstetric analgesia

Rapid and prolonged analgesia was obtained in all of 14 obstetric patients who received synthetic human beta-endorphin intrathecally at the time of delivery. Normal uterine contractions were maintained and all women were fully conscious and highly cooperative in the delivery process. No depression of respiration rate, cardiovascular or central nervous system was observed in any of the patients. Conditions of the infants evaluated by Apgar scoring were excellent. beta-endorphin must be administered intrathecally because it does not cross the blood-brain barrier; for the same reason, beta-endorphin cannot enter the central nervous system of the fetus as do opiates or other drugs commonly used as anesthetics or analgesics at the time of delivery.

Behavioral and biological effects of acute beta-endorphin injection in schizophrenic and depressed patients

In this double-blind study, beta-endorphin, 4-15 mg, was administered intravenously to 6 schizophrenic and 4 depressed patients. There were neither significant differences in behavioral ratings between beta-endorphin and placebo for the overall group nor for either the schizophrenic or depressed subgroup. Clinical worsening and improvement were observed in individual schizophrenic patients. There was no evidence of late-appearing therapeutic effects in 4 schizophrenic patients rated for 5 consecutive days after placebo and drug infusions. In 1 patient 10 mg of beta-endorphin produced neuroendocrine effects comparable to those produced by 5 mg of intravenously administered methadone; in 2 other patients it produced large increases in circulating opioid activity as determined by radioreceptor assay. These biological data support the notion that parenterally administered beta-endorphin exerts significant opiate-like activity in vivo.

Des-tyrosine-gamma-endorphin administration in chronic schizophrenics. A preliminary report

The beta-lipotrophin fragment des-tyrosine-gamma-endorphin (DT gamma E) has been reported to have antipsychotic properties. We administered the compound without other psychoactive drugs to a subpopulation of schizophrenic subjects. Male patients with chronic psychotic illness and previous long-term neuroleptic therapy were given DT gamma E at a similar dose and duration of treatment that have been reported to be effective. No improvement in psychotic symptoms occurred; plasma prolactin level, a parameter characteristically altered by neuroleptic treatment, did not change. The beneficial effects of DT gamma E in schizophrenia may be specific to a diagnostic category, may be dependent on past pharmacologic treatment, or may occur only in combination with other drugs.

Antipsychotic properties of Des-enkephalin-gamma-endorphin in treatment of schizophrenic patients

Animal experiments have shown that the gamma-endorphin fragment des-enkephalin-gamma-endorphin (DE gamma E; beta-lipotropin 66-77) is the shortest sequence with neuroleptic-like activity with potency comparable to des-tyrosine-gamma-endorphin. We postulated that DE gamma E may be an endogenous peptide implicated in psychopathologic disease, particularly schizophrenia. To investigate the purported antipsychotic action of DE gamma E, 23 patients with different types of relapsing schizophrenia were treated with DE gamma E dissolved in saline or placebo. Neuroleptic medication was continued during the experimental period. In the first single-blind trial, two patients were treated with 1 mg of DE gamma E and two with 10 mg of DE gamma E intramuscularly (IM) daily for ten days. In the second double-blind placebo-controlled trial 13 patients were treated with 3 mg of DE gamma E IM daily for ten days and six received placebo. Of the 17 patients treated with DE gamma E, two did not respond, 11 had a slight to moderate effect, and four responded markedly. No side effects were observed. The response to DE gamma E appeared to be negatively correlated with the dosage of neuroleptic medication and the duration of the last psychotic episode. These results support the hypothesis that disturbances in gamma-endorphin fragmentation might contribute to the pathogenesis of schizophrenic psychoses.

Protective effect of beta-casomorphin-7 on type 1 diabetes rats induced with streptozotocin

The present study was aimed to investigate the possible effects of beta-casomorphin-7, against hyperglycemia and free radical-mediated oxidative stress in streptozotocin-induced diabetic rats by assaying the blood glucose level and the activity of plasma enzymatic antioxidants, such as superoxide dismutase (SOD), catalase and glutathione peroxidase (GSH-Px). A significant increase in the levels of both blood glucose and oxidative stress with a predominant decrease in antioxidant status was observed in the diabetic rats when compared to control rats. After 15 days oral administration of beta-casomorphin-7 (7.5 x 10(-8) mol/day), the elevated blood glucose level was reduced. Oral administration of beta-CM-7 to diabetic rats showed an increase in the level of plasma insulin, the elevated plasma glucagon level was markedly reduced by the oral administration of beta-CM-7. Oral administration of beta-CM-7 to the diabetic group of rats also showed a significant elevation in the activity of SOD and catalase. Thus, the results of the present study suggest that beta-casomorphin-7 can protect rats from hyperglycemia and free radical-mediated oxidative stress in diabetic rats.

Synthesis and biological evaluation of cyclic endomorphin-2 analogs

In our previous paper we reported synthesis and biological activity of two cyclic analogs of endomorphin-2 (EM-2): Tyr-c(Lys-Phe-Phe-Asp)-NH(2) and Tyr-c(Asp-Phe-Phe-Lys)-NH(2), achieved by making an amid bond between Lys and Asp side-chains. The first analog did not bind to the mu-opioid receptor, the affinity of the second one was very low. In the present study, we describe the synthesis of four novel cyclic analogs of similar structure, but with d-amino acids in position 2 (D-Lys or D-Asp). All new analogs displayed high affinity for the mu-opioid receptor, were much more stable than EM-2 in rat brain homogenate and showed remarkable antinociceptive activity after intracerebroventricular (i.c.v.) administration. Analgesic effect of the most potent cyclic analog, Tyr-c(D-Lys-Phe-Phe-Asp)NH(2) was much stronger and longer lasting than that of EM-2. This analog elicited analgesia also after peripheral administration and this effect was reversed by concomitant i.c.v. injection of the mu-opioid antagonist, beta-funaltrexamine, which indicated that antinociception was mediated by the mu-opioid receptor in the brain. Central action of the cyclic analog gives evidence that it was able to cross the blood-brain barrier, most likely due to the increased lipophilicity. Our results demonstrate that cyclization might be a promising strategy to enhance bioavailability of peptides and may serve a role in the development of novel endomorphin analogs with increased therapeutic potential.

Osteogenic growth peptide effects on primary human osteoblast cultures: potential relevance for the treatment of glucocorticoid-induced osteoporosis

The osteogenic growth peptide (OGP) is a naturally occurring tetradecapeptide that has attracted considerable clinical interest as a bone anabolic agent and hematopoietic stimulator. In vivo studies on animals have demonstrated that the synthetic peptide OGP (10-14), reproducing the OGP C-terminal active portion [H-Tyr-Gly-Phe-Gly-Gly-OH] increases bone formation, trabecular bone density and fracture healing. In vitro studies performed on cellular systems based on osteoblastic-like cell lines or mouse stromal cells, have demonstrated that OGP (10-14) increases osteoblast proliferation, alkaline phosphatase (ALKP) activity and matrix synthesis and mineralization. In view of a potential application of OGP (10-14) in clinical therapy, we have tested different concentrations of OGP (10-14) on primary human osteoblast (hOB) cultures. We have observed significant increases of hOB proliferation (+35%), ALKP activity (+60%), osteocalcin secretion (+50%), and mineralized nodules formation (+49%). Our experimental model based on mature hOBs was used to investigate if OGP (10-14) could prevent the effects on bone loss induced by sustained glucocorticoid (GC) treatments. A strong decrease in bone formation has been attributed to the effects of GCs on osteoblastogenesis and osteocyte apoptosis, while an increase in bone resorption was due to a transient osteoblastic stimulation, mediated by the OPG/RANKL/RANK system, of osteoclasts recruitment and activation. Moreover, GCs act on hOBs decreasing the release of osteoprotegerin (OPG) a regulator of the RANKL/RANK interaction. Here, we provide evidences that OGP (10-14) inhibits hOB apoptosis induced by an excess of dexamethasone (-48% of apoptotic cells). Furthermore, we show that OGP (10-14) can increase OPG secretion (+20%) and can restore the altered expression of OPG induced by GCs to physiological levels. Our results support the employment of OGP (10-14) in clinical trials addressed to the treatment of different bone remodeling alterations including the GC-induced osteoporosis.

Effects of the synthetic analogue of methionine enkephalin FK 33-824 on psychotic symptoms

In an open pilot study, 9 schizophrenic patients were treated with the synthetic analogue of methionin-enkephalin FK 33-824 on two consecutive days in a dose of 0.5 mg on the first day, and 1.0 mg on the second day (infusion for 2 hours). 3 patients refused therapy during or after the first infusion; of the remaining 6 patients (2 hebephrenic, 4 paranoid type) 5 patients improved remarkably on the first and second day. The total BPRS-score and 4 of the 5 factors of the BPRS-scale were reduced significantly the day after treatment compared to pretreatment values. The improvement continued for 28-168 hours.

Endogenous opiates: 1980

Vast amounts of research have been done that have attempted to delineate the pharmacological and physiological effects of the endogenous opiate peptides. A great deal of knowledge has also been accumulated in a limited time span concerning the types and locations of the opiate receptors and peptides, as well as their functions. In 1980, reports were made concerning the effects of these peptides on analgesia, on tolerance and dependence, on activity, on learning and memory, on schizophrenia and other types of emotional disturbances, and on physiological responses such as eating and drinking, cardiovascular responses, and sexual function. Additional understanding was also gained concerning their interactions with neurotransmitters, other neuropeptides, and hormones. These and other studies published only in 1980 are reviewed in this paper, which is the third of an annual series.