Enkephalinase inhibition antagonizes the increased susceptibility to seizure induced by REM sleep deprivation

In order to elucidate the relationship between REM sleep and the enkephalinergic system, the effects of REM sleep deprivation (REMSD), stress and the enkephalinase inhibitor phosphoramidon on handling-induced convulsions were studied in mice. REMSD, stress and phosphoramidon (25–500 g icv) increased the frequency of handling-induced convulsions (HIC) in normal mice. However, only in the last two groups were HIC antagonized by naloxone (1 mg/kg IP). In REMSD mice, phosphoramidon decreased the frequency of HIC, this effect being abolished by naloxone. The increase of neuronal excitability during REMSD is suggested to be associated with an insufficiency of the enkephalinergic system.     

Repeated REM sleep deprivation after chronic haloperidol administration in the rat

Repeated haloperidol administration produces up-regulation of dopamine (DA) receptors. REM sleep deprivation (REMSD) does also, but in addition, has been shown to produce REM sleep rebound. Should DA receptor up-regulation play a role in REM sleep rebound, haloperidol could conceivably have effects similar to those observed following REMSD. This is the central question investigated in this study. Male Wistar rats were prepared for sleep recordings. They were randomly assigned to the following groups: group 1, REMSD by small platforms (40 h REMSD + 8 h recording); group 2, was the large platform control group (40 h in large platforms + 8 h of recording); group 3, received 2-week daily administration of haloperidol (3 mg/kg, IP) plus REMSD (40 h REMSD + 8 h of recording); group 4, 2-week administration of haloperidol (3 mg/kg) without sleep manipulation and at the end 40 h were allowed to elapse, following which 8 h of sleep recordings was carried out. In each group the sleep manipulation and/or sleep recordings were repeated five consecutive times. Repeated REMSD produced increases of REM sleep time after each recovery in group 1. Large platforms did not produce increases of REM sleep during the recovery trials. The 2-week administration of haloperidol plus REMSD prevented REM sleep rebound (group 3). The 2-week administration of haloperidol without sleep manipulation (group 4) produced a REM sleep reduction. Dopamine modulation seems not to be important for REM sleep rebound. Hypersensitivity of DA receptors developed after REMSD may be an epiphenomenon associated with this sleep manipulation, but seems not to participate in REM sleep enhancement after REMSD. Received: 27 December 1995/Final version: 17 December 1996     

REM sleep deprivation decreases the grooming and shaking behaviour induced by enkephalinase inhibitor or opiate withdrawal

Intraventricular administration of enkephalinase inhibitor, phosphoramidon (1 X 10(-8)-5.6 X 10(-7) moles ICV) induced a behavioural syndrome consisting of excessive grooming with the body scratching as the most prominent symptom and wet-dog-shakes (WDS). The frequency of the phosphoramidon-induced WDS and body scratching were decreased by the pretreatment with the opiate receptor blocking agent, naltrexone (2.9 X 10(-6) moles/kg IP). Both the phosphoramidon-induced WDS in naive rats and naloxone-precipitated withdrawal WDS were decreased in REM sleep deprived rats compared with animals allowed normal sleep (control and stress groups). The results are discussed in light of a possible functional insufficiency of endorphinergic system during REMSD. It has been suggested that this insufficiency might be a background to the increased neuronal excitability during REMSD.     

Effects of biperiden on sleep at baseline and after 72 h of REM sleep deprivation in the cat

We examined the effects of the muscarinic M1 antagonist biperiden in cats. In the first experiment a dose-response analysis was performed with intraventricular injection (IV ventricle) of biperiden. In the second experiment after REM sleep deprivation cats were injected with either biperiden (0.1 mg/kg) or saline. Biperiden produced a reduction in REM sleep percentage and an increase in REM sleep latency with these high doses. The 0.1 mg/kg biperiden dose, which did not suppress REM sleep at baseline, did reduce the REM sleep rebound. The present study suggests a modulatory role of biperiden on REM sleep regulatory processes. The fact that an effect of biperiden is noted only at the high doses suggests that at these doses the drug is influencing non-M1 receptors. Changes in the sensitivity of these receptors as a result of REM sleep deprivation might explain why a dose of biperiden will reduce REM sleep rebound, while being ineffective in suppressing REM sleep at baseline.     

REM sleep deprivation changes behavioral response to catecholaminergic and serotonergic receptor activation in rats

The effects of REM sleep deprivation (REMD) on apomorphine-induced aggressiveness and quipazine-induced head twitches in rats were determined. Forty-eight hr of REMD increased apomorphine-induced aggressiveness, and reduced (immediately after completing of REMD) or increased (96 hr after completing of REMD) quipazine-induced head twitches. Results are discussed in terms of similarity to pharmacological effects of other antidepressive treatments.     

The flower pot technique of Rapid Eye Movement (REM) sleep deprivation

This technique of REM sleep deprivation may make data interpretation difficult because it can lack selectivity, and because controls may suppress some REM sleep. To correct these difficulties, EEG recordings were made of rats placed in 4 situations for 96 hours: (1) baseline, (2) on 6.5 cm, or (3) 12.5 cm inverted flowerpots surrounded by water, (4) swimming in 10 cm water for 1 hr per 24 hr. Rats on the 6.5 cm pots had 57% as much REM sleep as baseline with no change in non-REM sleep. Rats on 12.5 cm pots initially had 55% as much REM sleep baseline, but by the fourth day increased to baseline levels. The swimming rats had no reduction in REM or non-REM sleep at any time, and thus seem to be a better control. The smaller the platform relative to the size of the rat, the greater the reduction in REM sleep - but at one point, non-REM sleep is decreased. The combination used here depresses REM sleep by about one half but does not reduce non-REM sleep.     

5-HT7 receptor deletion enhances REM sleep suppression induced by selective serotonin reuptake inhibitors, but not by direct stimulation of 5-HT1A receptor

5-HT₇ receptors are involved in REM sleep and possibly in mood disorders. REM sleep suppression and antidepressant-like behavior is observed in 5-HT₇^−/− mice and in rats treated with 5-HT₇ receptor antagonists. We recently demonstrated that pharmacological blockade of 5-HT₇ receptors enhances REM sleep suppression and antidepressant-like behavior induced by citalopram in rodents. It has been hypothesized that the effect of citalopram on sleep is essentially mediated by the activation of 5-HT_1A receptors. The present study investigates the impact of 5-HT₇ receptor gene deletion on the effect of various reuptake inhibitors on REM sleep and probes the role of 5-HT_1A receptors in this response. Three SSRIs (citalopram, fluoxetine and paroxetine) but not the tricyclic antidepressant desipramine had a significantly stronger REM sleep suppressive effect in 5-HT₇^−/− mice compared to 5-HT₇^+/+ mice. In contrast, REM sleep was similarly reduced in 5-HT₇^+/+ mice and 5-HT₇^−/− mice after treatment with the 5-HT_1A receptor agonist ipsapirone. Furthermore, both 5-HT₇^+/+ and 5-HT₇^−/− mice displayed the same increase in REM sleep duration produced by the 5-HT_1A receptor antagonist WAY-100635. These findings indicate that 5-HT₇ receptor deletion augments the effect of various SSRIs on REM sleep suppression and that this effect is distinct from those mediated via 5-HT_1A receptors.     

Intrathecal administration of a gap junction decoupler, an inhibitor of Na-K-2Cl cotransporter 1, or a GABAA receptor agonist attenuates mechanical pain hypersensitivity induced by REM sleep deprivation in the rat

We studied the hypothesis that some of the spinal mechanisms that are involved in neuropathic hypersensitivity play a role in hypersensitivity induced by REM sleep deprivation (REMSD). Rats with a chronic intrathecal (i.t.) catheter had REMSD of 48 h duration that induced hypersensitivity to mechanical stimulation. After REMSD, the animals were treated i.t. with carbenoxolone (a gap junction decoupler), bumetanide (a blocker of Na⁺-K⁺-2Cl⁻ cotransporter 1 or NKCC1), muscimol (a GABA_A receptor agonist), or pretreated intraperitoneally with minocycline (an inhibitor of microglia activation). Previously, all these treatments attenuated neuropathic hypersensitivity. Following REMSD, carbenoxolone, bumetanide and muscimol had a strong antihypersensitivity effect, whereas pretreatment with minocycline failed to prevent development of hypersensitivity. The results suggest that among spinal pain facilitatory mechanisms that are common to REMSD and neuropathy are NKCC1 blocker- and gap junction decoupler-reversible mechanisms. Moreover, there is a net pain inhibitory effect by spinal administration of an exogenous GABA_A receptor agonist following REMSD as shown earlier in neuropathy. In contrast, activation of spinal microglia may not be as important for the development of hypersensitivity induced by REMSD as following nerve injury.     

Possible role for the 5-HT<Subscript>1A</Subscript> receptor in the behavioral effects of REM sleep deprivation on free-operant avoidance responding in rat

Rationale REM sleep deprivation (REMSD) has been shown to increase rates of free-operant avoidance responding. Depletion of 5-hydroxytryptamine (5-HT, serotonin) levels produces similar effects on responding.Objective We studied whether the pharmacological activation of the 5-HT_1A receptor would produce effects on avoidance responding similar to REMSD and depleted 5-HT levels.Methods Rats were trained to lever press on a free-operant avoidance task. Dose-effect functions were established for 8-OH-DPAT (a 5-HT_1A receptor agonist) (0.1–1.0 mg/kg) and WAY 100635 (a 5-HT_1A receptor antagonist) (0.1–1.0 mg/kg). Rats were then exposed to REMSD (48 h) or equivalent control conditions, and then administered 8-OH-DPAT (0.6 mg/kg) and/or WAY 100635 (0.025–0.1 mg/kg).Results Injections of 8-OH-DPAT increased rates of avoidance responding in a dose-dependent manner, while WAY 100635 did not alter responding. The effect of 8-OH-DPAT was antagonized by pre-injection of WAY 100635. REMSD and injections of 8-OH-DPAT increased rates of avoidance responding and the effects of both manipulations were reversed by pre-injection of WAY 100635.Conclusions Activation of the 5-HT_1A receptor may be a mechanism by which REMSD increases rates of free-operant avoidance responding.     

Comparisons of hallucinogenic phenylisopropylamine binding affinities at cloned human 5-HT2A, 5-HT2B and 5-HT2C receptors

Since the classical hallucinogens were initially reported to produce their behavioral effects via a 5-HT₂ agonist mechanism (i.e., the 5-HT₂ hypothesis of hallucinogen action), 5-HT₂ receptors have been demonstrated to represent a family of receptors that consists of three distinct subpopulations: 5-HT_2A, 5-HT_2B, and 5-HT_2C receptors. Today, there is greater support for 5-HT_2A than for 5-HT_2C receptor involvement in the behavioral effects evoked by these agents. However, with the recent discovery of 5-HT_2B receptors, a new question arises: do classical hallucinogens bind at 5-HT_2B receptors? In the present study we examined and compared the binding of 17 phenylisopropylamines at human 5-HT_2A, 5-HT_2B, and 5-HT_2C receptors. Although there was a notable positive correlation (r>0.9) between the affinities of the agents at all three populations of 5-HT₂ receptors, structural modification resulted only in small differences in 5-HT_2B receptor affinity such that the range of affinities was only about 50-fold. As with 5-HT_2A and 5-HT_2C receptor affinity, there is a significant correlation (r>0.9, n=8) between 5-HT_2B receptor affinity and human hallucinogenic potency. Nevertheless, given that 5-HT_2A and 5-HT_2A/2C antagonists – antagonists with low affinity for 5-HT_2B receptors – have been previously shown to block the stimulus effects of phenylisopropylamine hallucinogens, it is likely that 5-HT_2A receptors play a more prominent role than 5-HT_2B and 5-HT_2C receptors in mediating such effects despite the affinity of these agents for all three 5-HT₂ receptor subpopulations.     

Peripheral 5-HT1B and 5-HT2A receptors mediate the nociceptive response induced by 5-hydroxytryptamine in mice

While the role of 5-hydroxytryptamine (5-HT, serotonin) in the nociceptive processing has been widely investigated in the central nervous system, information regarding its role in peripheral tissues is still lacking. Noteworthy, 5-HT induces phenotypic changes of nociceptors and peripheral injection induces pain in humans and nociceptive response in rodents. However, local receptors involved in 5-HT effects are not well characterized. Thus, we aimed to investigate the role of 5-HT and some of its receptors in the peripheral nociceptive processing in mice. Intraplantar injection of 5-HT (10, 20 or 40 μg) into the hind-paw of mice induced paw licking behavior, which was inhibited by previous intraplantar treatment with cyproheptadine (5-HT₁ and 5-HT₂ antagonist; 0.5 or 5 μg), mianserin (5-HT₂ and 5-HT₆ antagonist; 0.1 μg), isamoltane (5-HT_1B antagonist; 0.5 or 5 μg) and ketanserin (5-HT_2A antagonist; 0.1 or 1 μg), but not by BRL 15572 (5-HT_1D antagonist; 1 or 10 μg), ondansetron (5-HT₃ antagonist; 1, 5, 10 or 20 μg) and SB 269970 (5-HT₇ antagonist; 2.5 and 25 μg). Altogether, these results indicate the local involvement of 5-HT₁, 5-HT₂ and 5-HT₆, especially 5-HT_1B and 5-HT_2A, in the nociceptive response induced by 5-HT in mice, thus contributing to a better understanding of 5-HT role in the peripheral nociceptive processing. In addition, they also point to important species differences and the need of a wide evaluation of the peripheral nociceptive processing in mice as these animals have been increasingly used in studies investigating the cellular and molecular mechanisms mediating the nociceptive response.     

Disruption of passive avoidance memory by REM sleep deprivation: Methodological and pharmacological considerations

The present experiment were designed to examine more closely the variables responsible for the disruption of passive avoidance memory produced by REM sleep deprivation. In the pharmacological study it was found that imipramine could reverse the memory disruption exhibited by rats maintained on large platforms (presumably not REM-deprived) small platforms. In the methological study it was found that those animals maintained on the smallest platforms and therefore having the largest weight to area ratio exhibited the greatest degree of memory disruption. It is concluded that further modification and verification of the platform techniques of REM deprivation id required before firm conclusions about its neurochemical basis and behavioural functions can be made.     

Dopamine metabolism and receptor sensitivity in rat brain after REM sleep deprivation

Different dopaminergic mechanisms that could explain behavioral supersensitivity to amphetamine or apomorphine in REM-deprived rats were examined. Four days of REM sleep deprivation induced a highly significant elevation in striatal DOPAC relative to normal controls, but not to stress controls. DOPAC levels in frontal cortex were not affected in any of the groups. Post synaptic D₂ receptor number (B_max) and affinity (K_d) were unchanged in both terminal regions. Similarly, no changes in pre-synaptic receptor sensitivity (apomorphine-induced inhibition of tyrosine hydroxylase) occurred in striatum. A stress control group exhibited no changes in any of the biochemical measures in comparison with either the REM deprived group or unstressed controls. Thus, the enhanced response to dopamine agonists reported previously is not due to altered dopamine receptor sensitivity. Alternative hypotheses to explain enhanced responses to direct and indirect acting dopamine agonists are discussed.     

Differences in agonist-independent activity of 5-HT2A and 5-HT2C receptors revealed by heterologous expression

5-Hydroxytryptamine 5-HT_2A and 5-HT_2C receptors share many properties, including a common ability to stimulate phospholipase C. Traditionally, this activation was thought to be initiated only after agonist binding, in accordance with the ternary complex model of receptor function. Recently, though, the 5-HT_2C receptor was shown to deviate from this tenet by spontaneously isomerizing into the active receptor state, thereby activating G proteins in the absence of agonist. To determine if 5-HT_2A receptors share this property of constitutive activity, 5-HT_2A and 5-HT_2C receptor function was evaluated in transiently transfected NIH 3T3 fibroblasts. In 3T3 cells expressing 5-HT_2C receptors, agonist-independent phosphatidyl inositol hydrolysis was substantially elevated relative to mock-transfected cells. In contrast, expression of the 5-HT_2A receptor at the same density caused only a marginal increase in basal signaling. Control experiments in the current and previous papers establish that basal activity does not reflect contaminating serotonin. In addition, the magnitude of serotonin-induced signaling was the same in cells expressing either receptor, suggesting that the intrinsic ability of the two receptors to couple to G proteins is comparable. These data indicate that the 5-HT_2A receptor has a much lower intrinsic ability to spontaneously adopt or maintain the active receptor conformation than does the closely related 5-HT_2C receptor.

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Received: 25 August 1998 / Accepted: 30 October 1998     

Lithium increases slow wave sleep: possible mediation by brain 5-HT2 receptors?

The effect of lithium on slow wave sleep (SWS) was studied in ten normal male volunteers using home based cassette sleep recording and automatic sleep stage analysis. Lithium increased SWS, an effect consisten with a reduction in brain 5-HT₂ receptor function.     

Aggressiveness induced by marihuana and other psychotropic drugs in REM sleep deprived rats

In 96 hr REM sleep deprived rats given 5–40 mg/kg of Δ⁹-THC and several alcoholic extracts of marihuana induce dose dependent aggressive behavior. The aggressiveness appears after the first application of the drugs and is observable for at least 4 hr following the injection. The rats also develop a high degree of irritability. LSD-25 (0.02–0.08 mg/kg), mescaline (80 mg/kg), d-amphetamine (1.0 to 4.0 mg/kg) and ethanol (0.8–1.6 g/kg) failed to elicit either aggressiveness or irritability in the REM sleep deprived rats. On the other hand, 8 and 16 mg/kg of d-amphetamine induced aggressiveness which was, however, far below that observed in the marihuana treated animals. These data add further support to the previous findings that the acute effects of marihuana can be dramatically changed from depression, as observed in normal rats, to irritability and aggressiveness as observed in stressed animals.     

Potent antagonism of 5-HT(3) and 5-HT(6) receptors by olanzapine.

The interaction of the psychotropic agent olanzapine with serotonin 5-HT₃ and 5-HT₆ receptors was investigated. Olanzapine did not contract the isolated guinea pig ileum, but blocked contractions induced by the 5-HT₃ receptor agonist 2-methyl serotonin (2-CH₃ 5-HT) with a pK_B value of 6.38±0.03, close to the affinity of the 5-HT₃ receptor antagonist ondansetron. The atypical antipsychotic risperidone (1 μM) did not significantly inhibit 2-CH₃ 5-HT-induced contractions. Olanzapine had high affinity (pK_i=8.30±0.06) for human 5-HT₆ receptors in radioligand binding studies. Olanzapine did not stimulate [³⁵S]guanosine-5′-O-(3-thio)triphosphate ([³⁵S]GTPγS) binding to the G protein G_s in cells containing human 5-HT₆ receptors, but inhibited 5-HT-stimulated [³⁵S]GTPγS binding (pK_B=7.38±0.16). Among other antipsychotics investigated, clozapine antagonized 5-HT₆ receptors with a pK_B=7.42±0.15, ziprasidone was three-fold less potent, and risperidone, quetiapine and haloperidol were weak antagonists. Thus, olanzapine was not an agonist, but was a potent antagonist at 5-HT₆ receptors and had marked antagonism at 5-HT₃ receptors.     

芳烷酮哌嗪类化合物SCP-1和SCP-2与5-HT1,2受体的结合实验

目的研究芳烷酮哌嗪类化合物SCP-1和SCP-2与5-HT1和5-HT2受体体外是否有结合作用.方法5-HT1受体取材于大鼠大脑皮质,5-HT2受体取材于大鼠海马.采用受体-配体结合测定法测定10-3mol·L-1的SCP-1和SCP-2对5-HT1,5-HT2受体的最大结合率、半数抑制浓度(IC50)和Hill系数.结果10-3mol·L-1的SCP-1和SCP-2与5-HT1受体的最大结合率分别为75%和63%.SCP-1和SCP-2与5-HT1受体结合的IC50分别为1.584和5.495μmol·L-1,二者与5-HT1受体结合的Hill系数分别为0.98和1.02.10-3mol·L-1的SCP-1和SCP-2与5-HT2受体的最大结合率分别为92%和87%.SCP-1和SCP-2与5-HT2受体结合的IC50分别为1.0和2.512μmol·L-1,二者与5-HT2受体结合的Hill系数分别为0.86和0.88.结论SCP-1和SCP-2与5-HT1受体的结合方式是与单一受体位点结合,并且这种结合服从质量作用定律(Hill系数接近于1).SCP-1和SCP-2与5-HT2受体呈现不规则性结合,也可能有负相互作用或多种结合位点(Hill系数偏离1).     

Brown adipose tissue sympathetic nerve activity is potentiated by activation of 5-hydroxytryptamine (5-HT)1A/5-HT7 receptors in the rat spinal cord

In urethane-chloralose anesthetized, neuromuscularly blocked, ventilated rats, microinjection of NMDA (12 pmol) into the right fourth thoracic segment (T4) spinal intermediolateral nucleus (IML) immediately increased ipsilateral brown adipose tissue (BAT) sympathetic nerve activity (SNA; peak +492% of control), expired CO2 (+0.1%) heart rate (+48 beats min(-1)) and arterial pressure (+8 mmHg). The increase in BAT SNA evoked by T4 IML microinjection of NMDA was potentiated when it was administered immediately following a T4 IML microinjection of 5-hydroxytryptamine (5-HT, 100 pmol) or the 5-HT1A/5-HT7 receptor agonist, 8-OH-DPAT (600 pmol), (area under the curve: 184%, and 259% of the NMDA-only response, respectively). In contrast, T4 IML microinjection of the 5-HT2 receptor agonist, DOI (28 pmol) did not potentiate the NMDA-evoked increase in BAT SNA (101% of NMDA-only response). Microinjection into the T4 IML of the selective 5-HT1A antagonist, WAY-100635 (500 pmol), plus the 5-HT7 antagonist, SB-269970 (500 pmol), prevented the 5-HT-induced potentiation of the NMDA-evoked increase in BAT SNA. When administered separately, WAY-100635 (800 pmol) and SB-269970 (800 pmol) attenuated the 8-OH-DPAT-induced potentiation of the NMDA-evoked increase in BAT SNA through effects on the amplitude and duration of the response, respectively. The selective 5-HT2 receptor antagonist, ketanserin (100 pmol), did not attenuate the potentiations of the NMDA-evoked increase in BAT SNA induced by either 5-HT or 8-OH-DPAT. These results demonstrate that activation of 5-HT1A/5-HT7 receptors can act synergistically with NMDA receptor activation within the IML to markedly increase BAT SNA.