Endogenous opiates: 1990

Effects of electro-acupuncture on psychological distress in postmenopausal women

OBJECTIVES

To evaluate effects of electro-acupuncture (EA) on general psychological distress and relate to experience of climacteric symptoms in 30 postmenopausal women.

DESIGN

A randomised single-blind controlled design was used to evaluate effects of EA and extremely superficial needle insertion, with the latter serving as a near-placebo control.

SETTINGS

The Linköping University Hospital in Sweden.

INTERVENTIONS

Fourteen treatments during 12 weeks with follow-ups at 3 and 6 months.

OUTCOME MEASURES

General psychological well-being, mood and experience of climacteric symptoms.

RESULTS

Mood Scale improved only in EA group and not until 12 weeks compared to baseline, from 110 to 129 (P = 0.01), and to 120 at 3-month follow-up (P = 0.04). Mood was significantly better than control at 8 (P = 0.05) and 12 weeks (P = 0.01). Visual analogue scale estimation of climacteric symptoms was decreased at 4 weeks in both groups, and lasted throughout the study period, in EA group from 5 to 2 (P = 0.04) and in control group from 5 to 3 (P = 0.02) at 6-month follow-up. Well-being was ameliorated from 4 weeks in EA and from 8 weeks in control group until end of study (P = 0.01, P = 0.03). No significant differences on climacteric symptoms or well-being existed between the groups.

CONCLUSIONS

This study does not show that EA is better than superficial needle insertion for the amelioration of general psychological distress and experience of climacteric symptoms in women with vasomotor symptoms after menopause. However, the more pronounced effect on mood suggests that EA might have additional effects compared with superficial needle insertion.

Few oligo-amenorrheic athletes have vasomotor symptoms

OBJECTIVE

To assess whether women with athletic oligo-amenorrhea have vasomotor symptoms.

MATERIAL AND METHODS

A mailed questionnaire was sent to 252 female athletes about vasomotor symptoms. Identical questions were also mailed to 1523 peri- and postmenopausal women.

RESULTS

The prevalence of vasomotor symptoms was low in female athletes with oligo- and amenorrhea and similar to that found in athletes with regular menstruations. The prevalence was significantly lower than in menopausal women. Although more than a third of the menopausal women had hormone replacement therapy, 30% of them still had vasomotor symptoms at least every week compared with only 2% of the oligo-amenorrheic athletes.

CONCLUSION

Vasomotor symptoms are very uncommon in oligo-amenorrheic athletes, although many of them are hypoestrogenic. It was suggested that one factor contributing to these symptoms around menopause is low hypothalamic activity of beta-endorphins, which makes the thermoregulatory centre labile. On the other hand, supraphysiological activity in hypothalamic beta-endorphins may cause the oligo-amenorrhea in athletes, but may stabilise the thermoregulatory centre and thus prevent hot flushes.

Postmenopausal women without previous or current vasomotor symptoms do not flush after abruptly abandoning estrogen replacement therapy

BACKGROUND

Most but not all women suffer from vasomotor symptoms around menopause. The exact mechanisms behind these symptoms are unknown, but the rate of decline in estrogen concentrations has been suggested to affect the risk of hot flushes.

OBJECTIVE

The objective was to assess whether vasomotor symptoms were induced in women without previous such symptoms, when the women were given combined estradiol and progestagen therapy for 3 months, whereafter therapy was abruptly withdrawn.

MATERIALS AND METHOD

After randomization, 40 postmenopausal women without previous or current vasomotor symptoms were treated transdermally with either 50 micrograms/day 17 beta-estradiol or placebo during 14 weeks. During the 13th and 14th weeks, treatment was combined with oral medroxyprogesterone acetate 10 mg/day. Serum estradiol and follicle-stimulating hormone (FSH) concentrations were analysed before and after 12 weeks of therapy. Climacteric symptoms were assessed at the same intervals as well as 8 weeks after the end of therapy.

RESULTS

All women had low pretreatment levels of estradiol and high FSH concentrations. During estradiol therapy estradiol levels increased significantly, whereas FSH only decreased slightly. No woman developed vasomotor symptoms after withdrawal of therapy.

CONCLUSION

Postmenopausal women without previous or current vasomotor symptoms did not develop such symptoms when estrogen replacement therapy was first instituted and then abruptly stopped. Probably other factors than the rate with which estrogen concentrations decrease determine whether or not a woman will develop vasomotor symptoms. Evidently, estrogens can be prescribed to a woman who has no vasomotor symptoms, without much risk of inducing such symptoms if she decides to abandon therapy, even after 3 months of treatment.

Postmenopausal women with vasomotor symptoms have increased urinary excretion of calcitonin gene-related peptide

OBJECTIVES

To establish whether 24 h urinary excretion of the potent vasodilator calcitonin gene-related peptide (CGRP) was higher in postmenopausal women with vasomotor symptoms compared to the level in women without symptoms. We also wanted to establish whether urinary excretion of CGRP changed during the menstrual cycle in women of fertile age.

MATERIAL AND METHODS

Thirteen postmenopausal women with and 13 women without vasomotor symptoms were included. Urine was collected over 24 h and CGRP excretion was measured utilizing radio-immunoassay technique. Twenty-four hour CGRP excretion was also measured in ten fertile women with regular cycles in early follicular, preovulatory and midluteal phase.

RESULTS

Twenty-four hour urinary excretion of CGRP was significantly higher in women with vasomotor symptoms compared to non-flushing women (median 7.16 vs 5.15 pmol/24 h; P = 0.028). CGRP concentrations were stable throughout the ovulatory cycles.

CONCLUSION

The 24 h urinary excretion of CGRP is higher in women with vasomotor symptoms than in women without these symptoms. CGRP may be the mediator of vasodilator signals originating from the thermoregulatory center.

Food cravings, endogenous opioid peptides, and food intake: a review

Extensive research indicates a strong relationship between endogenous opioid peptides (EOPs) and food intake. In the present paper, we propose that food cravings act as an intervening variable in this opioid-ingestion link. Specifically, we argue that altered EOP activity may elicit food cravings which in turn may influence food consumption. Correlational support for this opioidergic theory of food cravings is provided by examining various clinical conditions (e.g. pregnancy, menstruation, bulimia, stress, depression) which are associated with altered EOP levels, intensified food cravings, and increased food intake.

Interaction of morphine and haloperidol on agonistic and motor behaviors of male mice

To further clarify the interaction between opioid and dopaminergic systems, the effects of simultaneous administration of morphine hydrochloride (1.25 or 2.5 mg/kg) and haloperidol (0.1 mg/kg) on aggressive behavior of male mice were explored. Isolated male mice (experimental animals) were confronted in a neutral area with anosmic, group-housed consepecifics (standard opponents) 30 min after injection of both compounds, and aggression was evaluated by estimation of times allocated to 11 different behavioral categories. In the first experiment (which functioned as a pilot study), the two doses of morphine were explored. In the second one, incorporating a more complete experimental design, only the lowest morphine dose was used and the animals were preselected by a previous aggression test. In attack behavior, morphine added to haloperidol counteracted, at least partially, the antiaggressive effect of the neuroleptic. In contrast, the impairing effects of haloperidol on motor activity were increased by the addition of morphine. These results show that the behavioral effects of dopaminergic antagonists are modulated by opioid influences and that opiates and dopaminergic agents interact in a different manner on motor and on aggressive behaviors.

Thermodynamic parameters of opioid binding in the presence and absence of G-protein coupling

We have investigated the thermodynamic parameters of various opioid ligands interacting with their receptors in rat brain membranes. Affinity constants (Ka), enthalpy and entropy values were obtained from homologous displacement experiments performed at 0, 24 and 33 degrees C. It was found that all the opioid agonists tested ([3H]dihydromorphine (DHM) mu alkaloid; [3H]DAMGO mu peptide; [3H]deltorphin-B delta peptide) display endothermic binding accompanied with a large entropy increase, regardless of their chemical structure (alkaloid or peptide), or of their mu or delta receptor selectivity. In contrast, binding of the antagonist naloxone is exothermic, mainly enthalpy driven. Na+ or Mg2+ results only in quantitative changes of the thermodynamic parameters. In the presence of the GTP-analog Gpp(NH)p; or Gpp(NH)p + Na+; or Gpp(NH)p + Na- + Mg2+ the affinity of DHM binding dramatically decreases which might reflect functional uncoupling of the receptor-ligand complex and G-proteins. This altered molecular interactions are also indicated by curvilinear van't Hoff plot and entropy increase. It is concluded that the thermodynamic analysis provides means of determining the underlying driving forces of ligand binding and helps to delineate its mechanism.

Distribution and changes in mu- and kappa-opiate receptors during the midlife neurodevelopmental period of Coho salmon, Oncorhynchus kisutch

Parr-smolt transformation (PST) in coho salmon is associated with a plasma thyroid hormone (PT4) surge and a critical period of neural development that includes axonal sprouting, neurogenesis, and surges of select neurotransmitters. Here we provide a description of the selectivity, distribution, and the changes in the density of mu- and kappa-opiate receptors during PST, as revealed by quantitative in vitro autoradiography of [3H]Tyr-D-Ala-Gly-NMe-Phe-Gly-ol ([3H]DAMGO) and [3H]ethylketocyclazocine ([3H]EKC), respectively. The concentration of mu-receptors increased significantly in select cell groups in the early stages of parr-smolt transformation, until a peak was reached at the time coinciding with the peak of the PT4 surge. In other cell groups, the peaks occurred 1 or 2 weeks later. With one exception, this increase was followed by a decrease in concentration. The brain areas showing the highest concentrations are the dorsal nucleus of the ventral telencephalic area, the glomerular region, the granular layer of the valvula cerebelli, the nucleus diffuses of the inferior lobe, and the nucleus diffuses of the torus lateralis. Other regions with distinctly elevated mu-receptor concentrations are the stratum griseum centrale of the optic tectum and the preoptic area. The distribution of kappa-receptors is more diffuse, and the densities are considerably lower. The overlap in distribution of mu- and kappa-receptors is considerable, but significant exceptions are noted. For example, the dorsomedial nucleus of the dorsal telencephalic area, the habenular nucleus, and the dorsomedial nucleus of the thalamus exhibit a surge in density of kappa-receptors at the time of the PT4 surge, while the density of mu-receptors in these nuclei remain very low throughout parr-smolt transformation. The kappa-receptor containing cell groups are not identifiable until 3 weeks before the PT4 surge because of low densities. The most prominently labeled kappa-receptor regions are the ventral and dorsal nuclei of the ventral telencephalic area, the medial and dorsal zones of the dorsal telencephalic area, the optic tectum (all layers), the dorsomedial nucleus of the thalamus, the torus lateralis of the ventral hypothalamus, and the preoptic area. An increase of mu- and kappa-opiate receptor densities in specific brain regions may reflect roles in the alteration of brain organization, olfactory imprinting, neuroendocrine activity or other physiological activities. The overall distribution of these receptors are relatively more extensive in salmon than in other vertebrates so far studied.

Memory retrieval enhancement by kappa opioid agonist and mu, delta antagonists

The present study sought to identify specific opioid receptor subtypes involved in the modulation of reactivation of amnesic or forgotten memory traces by use of a one-trial inhibitory avoidance training procedures in mice. The effects of naloxone, ICI 174,864 (mu and delta opioid receptor antagonists, respectively) and dynorphin (kappa agonist) were investigated. The results indicated that preretention test administration of naloxone (2 mg/kg) or ICI 174,864 (3 mg/kg) attenuated the amnesia and forgetting as indicated by prolongation of step-through latency. On the other hand, the activation of kappa opioid receptors by dynorphin (1 mg/kg) also showed reactivating effects both after amnesia and forgetting. On the basis of the parallelism of the effects for mu and delta opioid receptor antagonists and kappa agonist, and on the finding that all three opioids demonstrated a different degree of reactivation of amnesic and forgotten memory traces, it was concluded that mu, delta, and kappa opioid receptors contribute to the modulation of amnesia and forgetting by independent mechanisms.

Effect of lactation on hypothalamic preproenkephalin gene expression

Enkephalin appears to modulate several aspects of reproductive function in female rats. The purpose of this study was to determine if lactation influences preproenkephalin gene expression in one or more hypothalamic nuclei known to be involved in maternal or reproductive behavior and prolactin secretion. Lactating rats were killed on day 3 (LAC 3) or day 10 (LAC 10) of lactation. Controls consisted of regular 4-day cycling rats that were killed on diestrous day 1, with 9 to 12 females per group. We used in situ hybridization histochemistry to assess preproenkephalin gene expression in individual cells in the medial preoptic nucleus, anterior, medial and posterior arcuate nucleus, magnocellular and parvocellular aspects of paraventricular nucleus, and ventromedial nucleus. Preproenkephalin mRNA in the anterior arcuate nucleus increased to reach significance (P < 0.05) at day 10 of lactation. Levels in the medial arcuate nucleus increased significantly (P < 0.001) by day 3 of lactation (LAC 3) and remained elevated on day 10 (LAC 10). No significant differences between lactating and control rats were detected in preproenkephalin mRNA levels in the posterior arcuate nucleus, medial preoptic nucleus or in the ventromedial nucleus. Substantial levels of preproenkephalin mRNA were found in the paraventricular nucleus, particularly in a limited region of the magnocellular portion. However, these levels did not change with lactation. These data provide evidence for differential regulation of the preproenkephalin gene during lactation. This change may contribute to lactational hyperprolactinemia and suppressed GnRH secretion, leading to reproductive acyclicity.

The Tyr-MIF-1 family of peptides

A review of research on the Tyr-MIF-1 family of peptides is presented with emphasis on Tyr-MIF-1 and its structure, passage through the blood-brain barrier, and both opiate antagonist and agonist properties. Family members MIF-1, Tyr-W-MIF-1 and Tyr-K-MIF-1 are also included.

Stimulatory effect of opioid peptides and naloxone on rat spinal cord cells in primary dissociated culture

Opioid peptides leu-enkephalin, a synthetic analog of enkephalin dalargin and an opiate receptor blocker naloxone were studied for their morphological effect on the cells of dissociated cultures of rat spinal cord. Low density seeding of cells (3.10(5);6.10(5) cells/ml) on collagen substrate was performed to document that opioid peptides increase the number of cultured cells and neurite outgrowth and lead to the activation of the initiated processes of aggregate formation. Upon higher density of plating (5.10(6) cells/ml) with poly-L-lysine as a substrate, activation of the aggregate formation process was demonstrated, both opioid peptides and naloxone leading to an increase in the size of aggregates. Statistical treatment of the results obtained in this set of experiments documented that leu-enkephalin, dalargin and naloxone increased 2.2-, 2.2-2.6-, 2.4-fold, respectively, the size of aggregates compared to the control, i.e. the reaction of spinal cord cells to opioid peptides and opiate receptor blocker naloxon was unidirected. The total effect of opioid peptides and naloxon resulted in a 3.6-fold increase in the size of the aggregates compared to the control. The data obtained in this study allow the assumption that opioid peptides and naloxone, while activating spinal cord cells via receptors of a different type, manifest the properties of factors thus increasing survival and adhesion of spinal cord cells in culture.

Effects of estrogen on the number of neurons expressing beta-endorphin in the medial basal hypothalamus of the female guinea pig

The distribution pattern of immunoreactive beta-endorphin neurons was studied in female guinea pigs that were ovariectomized, and one week later were injected with 25 micrograms estradiol benzoate or oil. The animals (5 from each group) were perfused after 24 hours with 4% paraformaldehyde. The locations of beta-endorphin cells and fibers were determined using avidin-biotin immunohistochemistry on free-floating vibratome sections. beta-endorphin-immunoreactive fibers were distributed widely throughout specific regions of the rostral forebrain, similar to what has been described in other species. beta-endorphin cell bodies were found in the arcuate nucleus and in adjacent ventrolateral areas throughout the rostrocaudal extent of the basal hypothalamus. Cells immunoreactive to beta-endorphin were also present in the caudal part of the ventromedial nucleus of the hypothalamus. The number of beta-endorphin neurons was quantified in anatomically matched sections through the rostral, medial and caudal basal hypothalamus of estradiol benzoate- and oil-treated guinea pigs. Analysis of variance revealed that the number of immunoreactive beta-endorphin cells was significantly increased in all regions of the basal hypothalamus of estrogen-treated guinea pigs as compared to vehicle-treated animals (P < 0.01). These data indicate that in the guinea pig, the number of neurons expressing beta-endorphin is increased in the arcuate nucleus 24 hours after estrogen treatment.

CNS effects of peptides: a cross-listing of peptides and their central actions published in the journal Peptides, 1986-1993

The centrally mediated effects of peptides as published in the journal Peptides from 1986 to 1993 are tabulated in two ways. In one table, the peptides are listed alphabetically. In another table, the effects are arranged alphabetically. Most of the effects observed after administration of peptides are grouped, wherever possible, into categories such as cardiovascular and gastrointestinal. The species used in most cases has been rats; where other animals were used, the species is noted. The route of administration of peptides and source of information also are included in the tables, with a complete listing provided at the end. Many peptides have been shown to exert a large number of centrally mediated effects.

Evidence for an involvement of the mu-type of opioid receptor in the modulation of learning

Pavlovian conditioning of the rabbit's nictitating membrane response was used to determine whether the retardation of learning produced by enkephalin derivatives was mediated through an action on mu- or delta-opioid receptors. Intraventricular injection of the highly selective mu-agonist, [D-Ala2, MePhe4, Gly-ol5] enkephalin (DAMGO) significantly retarded (2 nmol) or completely blocked (20 nmol) the acquisition of conditioned responses. The retarded or blocked acquisition of conditioned responses produced by DAMGO could still be detected when the rabbits were tested two days after cessation of drug injections, suggesting that DAMGO had affected learning and not simply performance of conditioned responses. Intraventricular injection of a comparable dose (20 nmol) of the highly selective delta-agonist, [D-Pen2,5] enkephalin (DPDPE) did not retard learning. A higher dose of DPDPE (200 nmol), which would be expected to act at both mu- and delta-receptors, did produce a retardation of acquisition that was comparable to the effects of a 2-nmol dose of DAMGO. However, unlike DAMGO, the retardation of learning produced by this dose of DPDPE appeared to be due, at least in part, to a reduction in the aversive properties of the unconditioned stimulus. The retardation of learning produced by 2 nmol of DAMGO and 200 nmol of DPDPE was due to an action on an opioid receptor because this effect was blocked by a subcutaneous injection of naloxone (2.5 mumol/kg), a specific opioid antagonist. The stereoselective effects of the mu-opioid agonist levorphanol further confirmed that the retarded learning was mediated through actions at the mu-opioid receptor. Autoradiographic studies indicated that a 2-nmol, intraventricular dose of DAMGO achieved contents greater than 1 pmol/mg in tissue lying within 2 mm of the lateral ventricle, third ventricle and cerebral aqueduct. These data suggest that enkephalins produce a retardation of learning through an effect on the mu-type of opioid receptor and that at least one locus of their actions is produced at periventricular sites lying within 2 mm of the ventricles.(ABSTRACT TRUNCATED AT 250 WORDS)

Met-enkephalin-Arg6-Phe7 in spinal cord and brain following traumatic injury to the spinal cord: influence of p-chlorophenylalanine. An experimental study in the rat using radioimmunoassay technique

The possibility that trauma to the dorsal horn may affect the release and distribution of enkephalin was examined using the opioid peptide Met-Enk-Arg6-Phe7 (MEAP) as a marker in a rat model. The peptide content of samples of spinal cord and whole brain was measured using a radioimmunoassay (RIA) technique. In addition, the possible functional relation between this peptide and serotonin was evaluated using a pharmacological approach that included depletion of endogenous serotonin. A focal trauma to the right dorsal horn in the T10-11 segments (2 mm deep and 5 mm long) markedly modified the content of MEAP of the adjacent rostral and caudal segments of the cord, as well as the content of MEAP of the brain. Depletion of serotonin with p-CPA (an inhibitor of the synthesis of serotonin) significantly elevated the content of MEAP in the whole brain without affecting the regions of the spinal cord (except T9 level which showed a 25% decrease from an intact control group). Trauma to the spinal cord in the serotonin-depleted animals did not alter the content of MEAP further, as compared to a p-CPA-treated but untraumatized group. These results indicate that enkephalin (i) participates in the pathophysiology of spinal cord trauma and (ii) suggest that the peptide is somehow functionally related with serotonin.

Neurochemical-neuroendocrine systems in the brain controlling macronutrient intake and metabolism

Appetite, energy balance and body weight gain are modulated by diverse neurochemical and neuroendocrine signals from different organs in the body and diverse regions in the brain. The hypothalamus plays an important integrative function in this process, acting through a variety of systems that involve a close interaction between nutrients, amines, neuropeptides and hormones. These systems underlie normal nutrient intake and metabolism and are thought to be responsible for shifts in feeding behavior across the circadian cycle and fluctuations relating to gender and age in both rats and humans. Moreover, alterations in these normal neurochemical-neuroendocrine systems may be associated with abnormal eating patterns, such as anorexia nervosa, bulimia and obesity. Understanding the systems that control eating behavior might provide a foundation for the treatment and possible prevention of such disorders.