Reciprocal effects of chronic diazepam and melatonin on brain melatonin and benzodiazepine binding sites

Diazepam affects both level and amplitude of rat locomotor activity rhythm but has no effect on core body temperature

The present study investigates the effects of a chronic administration of diazepam, a benzodiazepine widely used as an anxiolytic, on locomotor activity and body core temperature rhythms in male Wistar rats housed under 12 : 12 light : dark (LD) cycle conditions. Diazepam was administered subcutaneously for 3 wks in a dosage of 3 mg/kg body weight/day, 1 h before the onset of darkness. Diazepam increased the level of locomotor activity from the first day until the end of treatment, and also increased the amplitude of the activity circadian rhythm, but only on the third wk of treatment. Diazepam exerted no effects on the length of the period and did not affect the phase of the locomotor activity rhythm. The body temperature rhythm of rats was affected neither by short-term (a single injection) nor by long-term (every day for 3 wks) diazepam treatment. Diazepam lacked effect on body core temperature even on the first day of administration, thereby ruling out the possibility of drug tolerance development. The fact that diazepam affects locomotor activity, but not core body temperature, suggests that different mechanisms mediate the actions of diazepam on locomotor activity and on core body temperature.

Melatonin for perceived sleep disturbances associated with benzodiazepine withdrawal among patients in methadone maintenance treatment: a double-blind randomized clinical trial

AIMS

To evaluate the effectiveness of melatonin in attenuating sleep difficulties during benzodiazepine (BDZ) withdrawal.

DESIGN

Double-blind cross-over control study.

SETTING

Methadone maintenance treatment clinic.

PARTICIPANTS

Eighty patients enrolled at a community methadone maintenance clinic recruited to a BDZ withdrawal programme.

INTERVENTION

Melatonin (5 mg/day) or placebo: 6 weeks one arm, 1 week washout, 6 weeks other arm.

MEASUREMENTS

Urine BDZ; self-reported Pittsburgh Sleep Quality Index (PSQI) and the Center for Epidemiologic Studies Depression (CES-D) questionnaires administered at baseline, and at 6, 7 and 13 weeks.

FINDINGS

Sixty-one patients (77.5% in the 'melatonin first' condition and 75% in the 'placebo first' condition) completed 6 weeks of treatment, showing a similar BDZ discontinuation rate of 11/31 and 11/30, respectively. PSQI scores were significantly lower (indicating better sleep quality) in the 22 patients who discontinued BDZ (8.9 +/- 0.9) than in 39 with urine BDZ (11.2 +/- 0.7, P = 0.04). Sleep quality in patients who continued abusing BDZ improved more in the 'melatonin first' group than in the 'placebo first' group, with no differences in sleep quality improvement in patients who stopped BDZ. CONCLUSION Most improvement in sleep quality was attributed to BDZ discontinuation. Although melatonin did not enhance BDZ discontinuation, it improved sleep quality, especially in patients who did not stop BDZ.

Effects of melatonin and agomelatine in anxiety-related procedures in rats: interaction with diazepam

The anxiolytic potential of melatonin and agomelatine, a potent MT(1/2) receptor agonist, and their combined effects with diazepam, were investigated in rats using the punished drinking test, the safety signal withdrawal operant paradigm, the elevated-plus-maze and hypophagia-induced novelty. In the punished drinking test, evening injections of melatonin (80 mg/kg, IP, but not 20 and 40 mg/kg) and agomelatine (40 mg/kg, IP) increased the number of foot shocks received. However, neither melatonin (40-80 mg/kg) nor agomelatine (20-40 mg/kg) released response suppression during the period associated with the safety signal withdrawal and affected rats' behaviour in the elevated-plus-maze. Furthermore, agomelatine (40 mg/kg) did not enhance food consumption in unfamiliar environment. However, the co-administration of melatonin (80 mg/kg) or agomelatine (20-40 mg/kg) with diazepam, at a dose (0.25 mg/kg) inactive on its own, induced an anxiolytic-like effect in the punished drinking test and the elevated plus-maze. These results indicate that, although mostly devoid of anxiolytic-like action per se, melatonin and agomelatine can potentiate the anxiolytic effects of diazepam.

Effect of melatonin and diazepam on the dissociated circadian rhythm in rats

The main structures involved in the circadian system in mammals are the suprachiasmatic nuclei (SCN) of the hypothalamus. The SCN contain multiple autonomous single-cell circadian oscillators that are coupled among themselves, generating a single rhythm. However, under determined circumstances, the oscillators may uncouple and generate several rhythmic patterns. Rats exposed to an artificially established 22-h light-dark cycle (T22) express two stable circadian rhythms in their motor activity that reflect the separate activities of two groups of oscillators in the morphologically well-defined ventrolateral and dorsomedial SCN subdivisions. In the experiments described in this paper, we studied the effect of melatonin and diazepam (DZP) administration in drinking water on the dissociated components of rat motor activity exposed to T22, to deduce the possible mechanism of these drugs on the circadian system. In order to suppress the endogenous circadian rhythm of melatonin, in some of the rats the pineal gland or the superior cervical ganglia were removed. The results show that melatonin or DZP treatment increased the manifestation of the light-dependent component to the detriment of the manifestation of the non-light-dependent component and that melatonin, but not DZP, shortens the period of the non-light-dependent component. These findings suggest that both DZP and melatonin favor entrainment to external light, and that melatonin could also act on the SCN, producing changes in the period of the circadian cycle.

Improvement of sleep quality by controlled-release melatonin in benzodiazepine-treated elderly insomniacs

Benzodiazepines are widely used in the elderly population for the initiation of sleep. However, very frequently, complaints about poor sleep maintenance persist despite benzodiazepine treatment. Melatonin, a hormone produced by the pineal gland at night, is involved in the regulation of the sleep/wake cycle. Melatonin production decreases with age and can also be inhibited by benzodiazepines. We have recently reported on the association between insomnia and impaired melatonin output in the elderly. In the present study we have investigated the efficacy of melatonin replacement therapy in improving sleep in 21 elderly subjects who have been taking benzodiazepines and had low melatonin output. In a randomized, double-blind, crossover designed study the subjects were treated for three weeks with 2 mg per night of controlled-release melatonin and for 3 weeks with placebo, 2 h before desired bedtime with a 1-week washout period between treatment periods. Subjects' sleep was assessed by wrist actigraphy. Melatonin treatment significantly increased sleep efficiency and total sleep time and decreased wake after sleep onset, sleep latency, number of awakenings and fragmental index, as compared to placebo. The results of our study indicate that melatonin replacement therapy can improve sleep quality in the elderly and that the beneficial effects are augmented in the presence of benzodiazepines.

Anxiolytic properties of agomelatine, an antidepressant with melatoninergic and serotonergic properties: role of 5-HT2C receptor blockade

RATIONALE

The novel antidepressant agent, agomelatine, behaves as an agonist at melatonin receptors and as an antagonist at serotonin (5-HT)(2C) receptors.

OBJECTIVES

To determine whether, by virtue of its antagonist properties at 5-HT(2C) receptors, agomelatine elicits anxiolytic properties in rats.

METHODS

Employing a combined neurochemical and behavioural approach, actions of agomelatine were compared to those of melatonin, the selective 5-HT(2C) receptor antagonist, SB243,213, and the benzodiazepine, clorazepate.

RESULTS

In unfamiliar pairs of rats exposed to a novel environment, agomelatine enhanced the time devoted to active social interaction, an action mimicked by clorazepate and by SB243,213. In a Vogel conflict procedure, agomelatine likewise displayed dose-dependent anxiolytic activity with a maximal effect comparable to clorazepate, and SB243,213 was similarly active in this procedure. In a plus-maze procedure in which clorazepate significantly enhanced percentage entries into open arms, agomelatine revealed only modest activity and SB243,213 was inactive. Further, like SB243,213, and in contrast to clorazepate, agomelatine did not suppress ultrasonic vocalizations emitted by rats re-exposed to an environment associated with an aversive stimulus. Whereas clorazepate reduced dialysate levels of 5-HT and noradrenaline in hippocampus and frontal cortex of freely moving rats, agomelatine did not affect extracellular levels of 5-HT and elevated those of noradrenaline. SB243,213 acted similarly to agomelatine. Melatonin, which did not modify extracellular levels of 5-HT or noradrenaline, was ineffective in all models of anxiolytic activity. Furthermore, the selective melatonin antagonist, S22153, did not modify anxiolytic properties of agomelatine in either the social interaction or the Vogel Conflict tests.

CONCLUSIONS

In contrast to melatonin, and reflecting blockade of 5-HT(2C) receptors, agomelatine is active in several models of anxiolytic properties in rodents. The anxiolytic profile of agomelatine differs from that of benzodiazepines from which it may also be distinguished by its contrasting influence on corticolimbic monoaminergic pathways.

Effects of diazepam and its metabolites on nocturnal melatonin secretion in the rat pineal and Harderian glands. A comparative in vivo and in vitro study

We investigated the effects of diazepam (DZP) and its three metabolites: nordiazepam (NZP), oxazepam (OZP), and temazepam (TZP) on pineal gland nocturnal melatonin secretion. We looked at the effects of benzodiazepines on pineal gland melatonin secretion both in vitro (using organ perifusion) and in vivo in male Wistar rats sacrificed in the middle of the dark phase. We also examined the effects of these benzodiazepines on in vivo melatonin secretion in the Harderian glands. Neither DZP (10(-5)-10(-6)M) nor its metabolites (10(-4)-10(-5)M) affected melatonin secretion by perifused rat pineal glands in vitro. In contrast, a 10(-4)M suprapharmacological concentration of DZP increased melatonin secretion of perifused pineal glands by 70%. In vivo, a single acute subcutaneous administration of DZP (3 mg/kg body weight) significantly affected pineal melatonin synthesis and plasma melatonin levels, while administration of the metabolites under the same conditions did not. DZP reduced pineal melatonin content (-40%), N-acetyltransferase activity (-70%), and plasma melatonin levels (-40%), but had no affects on pineal hydroxyindole-O-methyltransferase activity. Neither DZP nor its metabolites affected Harderian gland melatonin content. Our results indicate that the in vivo inhibitory effect of DZP on melatonin synthesis is not due to the metabolism of DZP. The results also show that the control of melatonin production in the Harderian glands differ from that observed in the pineal gland.

Evaluation of plasma levels of melatonin after midazolam or sodium thiopental anesthesia in children

Midazolam and sodium thiopental are two commonly used drugs in anesthesia for minor surgical procedures in children. A relationship exists between benzodiazepines (BNZ), barbiturates and melatonin. Whereas these drugs increase pineal melatonin production, the indoleamine amplifies the effects of both BNZ and barbiturates on the central nervous system (CNS). Our purpose was thus to analyze the plasma levels of melatonin before and during midazolam or sodium thiopental anesthesia in children subjected to ambulatory surgical procedures. Midazolam (0.4 mg/kg) or sodium thiopental (5 mg/kg) were administered i.v. to 33 and 32 children (aged between 2 and 14 yr), respectively, and blood samples were taken before and 5, 10 and 20 min after the drugs were administered. Melatonin was measured in plasma by a commercial radioimmunoassay kit previously standardized in our laboratory. The results showed that neither midazolam nor sodium thiopental anesthesia significantly affected the levels of melatonin studied at anytime. Significant correlations were found comparing the levels of melatonin between the different times studied. These results suggest that midazolam or sodium thiopental did not affect melatonin production by the pineal gland, thus avoiding a possible potentiating effect of the indoleamine on the central effects of these drugs during anesthesia. However, the possibility that changes in melatonin had been masked by the antioxidant role of the neurohormone are discussed.

Assessment of melatonin's ability to regulate cytokine production by macrophage and microglia cell types

Evidence in support of melatonin's role as an immunomodulator is incomplete and, in some cases, contradictory. The present studies determined whether melatonin modulates the activity of stimulated macrophages. In vitro lipopolysaccharide (LPS, 10-1000 ng/ml) treatment of alveolar, splenic and peritoneal macrophages isolated from mice and/or rats resulted in a dose-dependent increase in interleukin-1beta (IL-1beta) and tumor necrosis factor (TNF-alpha) secretion. Treatment with melatonin (10(-10)-10(-6) M) prior to the addition of LPS, had no effect on IL-1beta or TNF-alpha release. Additionally, melatonin had no effect on stimulated BV2 microglial cell line cytokine secretion. To determine whether melatonin had an indirect effect on macrophage cytokine release via T cells, melatonin was added to unfractionated mouse spleen cells. Again, melatonin showed no priming effect on LPS-stimulated spleen cells. These results suggest that melatonin has no direct or indirect effect on mouse and rat macrophages. In vivo studies, where melatonin was continuously available in the drinking water, showed that melatonin did not have a priming effect on LPS-stimulated mouse peritoneal macrophages. These findings suggest that melatonin is not an important modulator of macrophage and microglia function.

Melatonin reduces anxiety induced by lipopolysaccharide in the rat

In male Sprague-Dawley rats intraperitoneal (i.p.) injection of Escherichia coli lipopolysaccharide (0.25, 0.50 and 1 mg/kg) increased anxiety levels. This effect was reversed by a prior, concomitant, and subsequent i.p. treatment with melatonin (4 and 6 mg/kg). As the effects of melatonin upon the actions induced by lipopolysaccharide were reversed by the melatonin receptor antagonist luzindole (30 and 60 mg/kg, i.p.), we argued that they are, but not only, melatonin receptor mediated. These findings, in accordance with our previous works, suggest that melatonin could be useful in the treatment of sickness behaviour associated with systemic infection diseases or as adjuvant in the anti-anxiety therapy.

Rapid reversal of tolerance to benzodiazepine hypnotics by treatment with oral melatonin: a case report

A 43 year old woman had suffered from insomnia for the past 11 years and was being treated with benzodiazepines. All attempts to stop benzodiazepine treatment resulted in withdrawal symptoms and a renewal of the insomnia. Treatment with 1 mg of controlled release melatonin enabled the patient to completely cease any benzodiazepine use within two days, with an improvement in sleep quality and no side effects. Examination of urinary 6-sulphatoxymelatonin levels before the melatonin treatment indicated that the levels were very low and lacked the typical circadian rhythm of excretion. Reexamination of 6-sulphatoxymelatonin levels during melatonin treatment revealed the existence of a normal circadian rhythm of excretion. This case may suggest that some of the people suffering from insomnia and addicted to benzodiazepines may successfully undergo withdrawal from these drugs and improve their sleep by means of treatment with melatonin. The results of this single case study warrant further investigation of a larger population by means of a double-blind placebo-drug study.