Some endorphin derivatives and hydrocortisone prevent EEG limbic seizures induced by corticotropin-releasing factor in rabbits

A Microelectrode Array Modified by PtNPs/PB Nanocomposites Used for the Detection and Analysis of Glucose-Sensitive Neurons under Different Blood Glucose States

Hypoglycemia state damages the organism, and glucose-excited and glucose-inhibited neurons from the ventral medial hypothalamus can regulate this state. Therefore, it is crucial to understand the functional mechanism between blood glucose and electrophysiology of glucose-excited and glucose-inhibited neurons. To better detect and analyze this mechanism, a PtNPs/PB nanomaterials modified 32-channel microelectrode array with low impedance (21.91 ± 6.80 kΩ), slight phase delay (-12.7° ± 2.7°), high double layer capacitance (0.606 μF), and biocompatibility was developed to realize in vivo real-time detection of the electrophysiology activities of glucose-excited and glucose-inhibited neurons. The phase-locking level of some glucose-inhibited neurons elevated during fasting (low blood glucose state) and showed theta rhythms after glucose injection (high blood glucose state). With an independent oscillating ability, glucose-inhibited neurons can provide an essential indicator to prevent severe hypoglycemia. The results reveal a mechanism for glucose-sensitive neurons to respond to blood glucose. Some glucose-inhibited neurons can integrate glucose information input and convert it into theta oscillating or phase lock output. It helps in enhancing the interaction between neurons and glucose. Therefore, the research can provide a basis for further controlling blood glucose by modulating the characteristics of neuronal electrophysiology. This helps reduce the damage of organisms under energy-limiting conditions, such as prolonged manned spaceflight or metabolic disorders.

Corticotropin releasing factor (CRF) in the hippocampus of the mouse pilocarpine model of status epilepticus

We investigated the cellular localization and progressive changes of corticotropin releasing factor (CRF) in the mouse hippocampus, during and after pilocarpine induced status epilepticus (PISE) and subsequent epileptogenesis. We found that CRF gene expression was up-regulated significantly at 2h during and 1d after PISE in comparison to control mice. Immunohistochemical analysis showed that the number of CRF and Fos immunoreactive cells was increased significantly in the strata oriens and pyramidale of CA1 area and in the stratum pyramidale of CA3 area at 2h during and 1d after PISE. CRF was induced in calbindin (CB) or calretinin (CR) immunoreactive interneurons in stratum oriens at 2h during PISE. It suggests that induced CRF may be related to the over excitation of hippocampal neurons and occurrence of status epilepticus. It may also cause excitoneurotoxicity and delayed loss of CA3 and CA1 pyramidal neurons, leading to the onset of epilepsy.

Neurochemistry and epileptology

This paper gives an account of the global evolution of (neuro-)chemistry in epileptology with an emphasis on the role of the International League Against Epilepsy (ILAE), which declared in its constitution a mission "to make the epilepsy-problem the object of special study and to make practical use of the results of such study." As Epilepsia is the scientific journal of the ILAE, the review emphasizes papers published in the journal.

Naloxone prevents cell-mediated immune alterations in adult mice following repeated mild stress in the neonatal period

1. Mild stress plus mild pain (solvent injection) applied daily to neonatal mice induces hormonal, behavioural and metabolic changes perduring in the adult life. 2. We investigated whether daily mild stress to neonatal mice induces also long-term defined changes of immune response, and whether immune changes are prevented through repeated administration of the opioid antagonist naloxone. 3. Mild stress plus solvent injection administered from birth to the 21st postnatal day causes not only behavioural and metabolic changes, but also long-term (up to 110 days of life) splenocytes modifications, consisting in: increased release of the Th-1 type cytokines interleukin-2 (IL-2) (from an average of 346 to 788 pg ml(-1)), interferon-gamma (from 1770 to 3942) and tumour necrosis factor-alpha (from 760 to 1241); decreased release of the Th-2 type cytokines IL-4 (from 49.1 to 28.4) and IL-10 (from 1508 to 877). Moreover, enhanced natural killer-cell activity; enhanced proliferative splenocytes properties in resting conditions and following phytohemoagglutinin and concanavalin-A stimulation are observed. Immunological, behavioural and metabolic changes are prevented by the opioid antagonist (-)naloxone (1 mg kg(-1) per day s.c., administered instead of solvent) but not by the biologically inactive enantiomorph (+)naloxone. 4. In conclusion, endogenous opioid systems sensitive to naloxone are involved in long-lasting enhancement of the Th-1 type cytokines and cell-mediated immunological response caused by repeated mild stress administered postnatally.

Guinea-pigs treated with beta-endorphin fragments DTgammaE and DEgammaE exhibit reduced morphine inhibition of electrically-induced contractions

The effect exerted by two gamma-endorphin derivatives (DTgammaE and DEgammaE) was investigated on morphine-induced inhibition on the electrically contractions of guinea pig ileum in vitro. Morphine (1x10(-8)-5x10(-8)-1x10(-7) M) dose dependently and significantly reduced the E.C. of guinea pig ileum, IC50=6.5x10(-8) M (Confidence limits: 3.7x10(-8)-9.1x10(-8)). DTgammaE and DEgammaEper se (1x10(-6)-5x10(-6)-1x10(-5) M) did not modify significantly the E.C. of guinea pig ileum. Furthermore, DTgammaE or DEgammaE injection 10-30-60 min before morphine, did not affect the inhibitory effect of morphine on the E.C. of guinea pig ileum. By contrast, ilea from guinea-pigs treated for 4 days with DTgammaE or DEgammaE (1 mg/Kg/i.p.) resulted less sensitive to the inhibitory effect of morphine, IC50=8.3x10(-7) M (Confidence limits: 1.4x10(-6)-3.5x10(-7)) for DTgammaE and IC50=7.7x10(-7) M (Confidence limits: 2.7x10(-6)-8.7x10(-7)) for DEgammaE. Our results indicate that chronic treatment of guinea pigs with DTgammaE or DEgammaE induces a significant reduction of the inhibitory effect of morphine on the E.C. of guinea-pig ileum thus confirming an important functional interaction between gamma-endorphin derivatives and opioid system.

Actinomycin D blocks the reducing effect of dexamethasone on amphetamine and cocaine hypermotility in mice

1. The present study examined a time-course effect of dexamethasone (DEX) on amphetamine and cocaine-induced hypermotility in mice and the influence of actinomycin D (dactinomycin), a protein synthesis inhibitor, on DEX effects. 2. Amphetamine (5 mg/kg IP) and cocaine (10 mg/kg IP) increased markedly the locomotor activity of mice, whereas DEX alone (0.1-1.0-10 mg/kg IP) did not modify the activity of control mice. 3. DEX pretreatment 0, 15, 30, 60 and 120 min before amphetamine or cocaine strongly decreased both amphetamine and cocaine effects, but no dose-related effect was observed. 4. The time-course study performed with DEX revealed differences in its reducing effect on cocaine and amphetamine hypermotility when the groups of animals treated with the steroid immediately before the cocaine (or amphetamine) injection were compared to those treated with the steroid later (15, 30, 60 and 120 min). 5. Furthermore, actinomycin D was able to block the reducing effect of DEX on both amphetamine and cocaine hypermotility. 6. Therefore, considering that the administration time of the steroid seems to be an important factor for reducing both cocaine and amphetamine hypermotility, and actinomycin D was able to block the reducing effect of the steroid, our study suggests that DEX exerts its reducing effect through a genomic activation.

Dexamethasone pretreatment reduces the psychomotor stimulant effects induced by cocaine and amphetamine in mice

1. The present study examined a comparison of the effect of DEX on psychomotor stimulant effects of cocaine and amphetamine in mice by using the locomotor activity test. 2. Cocaine (10 mg/kg/i.p.) and amphetamine (5 mg/kg/i.p.) increased markedly locomotor activity of mice whereas DEX per se (0.1-1.0-10 mg/kg/i.p.) did not modify the activity of control mice. 3. DEX pretreatment decreased the stimulating effects induced both by cocaine and amphetamine but no consistent dose-related effects were observed. 4. The results suggest that DEX may play an important role on the stimulating effects of cocaine and amphetamine and that it may be of some utility in the clinical management of psychostimulants abuse.

Dexamethasone-induced selective inhibition of the central mu opioid receptor: functional in vivo and in vitro evidence in rodents

1. Endogenous corticosteroids and opioids are involved in many functions of the organism, including analgesia, cerebral excitability, stress and others. Therefore, we considered it important to gain information on the functional interaction between corticosteroids and specific opioid receptor subpopulations. 2. We have found that systemic administration (i.p.) of the potent synthetic corticosteroid, dexamethasone, reduced the antinociception induced by the highly selective mu agonist, DAMGO or by less selective mu agonists morphine and beta-endorphin administered i.c.v.. On the contrary dexamethasone exerted little or no influence on the antinociception induced by a delta 1 agonist, DPDPE and a delta 2 agonist deltorphin II. Dexamethasone potentiated the antinociception induced by the kappa agonist, U50,488. 3. In experiments performed in an in vitro model of cerebral excitability in the rat hippocampal slice, dexamethasone strongly prevented both the increase of the duration of the field potential recorded in CA1, and the appearance and number of additional population spikes induced by mu receptor agonists. 4. In both models pretreatment with cycloheximide, a protein synthesis inhibitor, prevented the antagonism by dexamethasone of responses to the mu opioid agonists. 5. Our data indicate that in the rodent brain there is an important functional interaction between the corticosteroid and the opioid systems at least at the mu receptor level, while delta and kappa receptors are modulated in different ways.

Effect of des-tyrosine-gamma-endorphin on neocortical spike-and-wave spindling in DBA/2J mice

The effect of a beta-endorphin cleavage product devoid of opioid effects, des-tyrosine-gamma-endorphin (DT gamma E) on the neocortical spike-and-wave spindling episodes in the electrocorticogram (ECoG) of DBA/2J mice was studied. DT gamma E (0.01-1.0 mg/kg, i.p.) dose dependently reduced the spike-and-wave bursts duration. However, the low dose did not induce consistent modifications of the spike-and-wave bursts number while the dose of 0.1 and 1.0 mg/kg induced a progressive diminution. Furthermore, at all doses DT gamma E did not induce any alterations of the spike-and-wave bursts amplitude, frequency, and desynchronized activity when compared to the pre-drug period. These results indicate that this beta-endorphin fragment may affect brain excitability.

Pathophysiology of massive infantile spasms: perspective on the putative role of the brain adrenal axis

Massive infantile spasms are an age-specific seizure syndrome of infancy. Uniquely, the spasms respond to hormonal manipulation using adrenocorticotropic hormone (ACTH) or glucocorticoids. A hypothesis explaining the efficacy of hormonal therapy, age-specificity, multiple causative factors, and spontaneous resolution of infantile spasms is presented. Corticotropin-releasing hormone (CRH), an excitant neuropeptide suppressed by ACTH/steroids, is implicated. Evidence for the age-specific convulsant properties of CRH is presented, and a putative scenario in which a stress-induced enhancement of endogenous CRH-mediated seizures is discussed. Clinical testing of the CRH-excess theory and its therapeutic implications are suggested.

Des-tyrosine-gamma-endorphin effects on morphine analgesia in mice

1. The effects that were induced by a beta-lipotropin fragment des-tyrosine-gamma-endorphin (DT gamma E) devoid of opiate activity that was administered intraperitoneally or intracerebroventricularly to mice under morphine analgesia were investigated. The interaction of this peptide with the analgesic effects of morphine was examined using the hot plate and the tail flick test. 2. Intraperitoneal acute treatment with DT gamma E did not change the analgesic effects of morphine. 3. Intraperitoneal semi-chronic treatment performed for 4 days with DT gamma E enhanced morphine analgesic effects. 4. The intracerebroventricular acute treatment with DT gamma E reduced morphine analgesia in a dose-dependent way. 5. These results indicate that DT gamma E, although devoid of opioid activity per se, may interact with the opioid system, probably through an indirect mechanism.

Corticotropin-releasing hormone-induced seizures in infant rats originate in the amygdala

The neuroanatomical substrate of seizures induced by picomolar amounts of corticotropin-releasing hormone in infant rats was investigated. Electrographic and behavioral phenomena were monitored in 42 rat pups aged 5 to 22 days. Rat pups carried bipolar electrodes implanted in subcortical limbic structures, as well as cortical electrodes and intracerebroventricular cannulae. The administration of corticotropin-releasing hormone produced age-specific seizures within minutes, which correlated with rhythmic amygdala discharges. Paroxysmal hippocampal and cortical discharges developed subsequently in some rats. Corticotropin-releasing hormone-induced electrographic and behavioral seizures originate in the amygdala.

Endogenous opiates: 1990

This paper, an examination of works published during 1990, is thirteenth in a series of our annual reviews of the research involving the behavioral, nonanalgesic, effects of the endogenous opiate peptides. The specific topics this year include stress; tolerance and dependence, eating; drinking; gastrointestinal, renal, and hepatic functions; mental illness; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; locomotor activity; sex, pregnancy, development, and aging; immunological responses; and other behavior.