Central serotonergic effects of m-chlorophenylpiperazine (mCPP) among normal control adolescents

Pharmacokinetic, sedative, and physiological effects of oral compounded formulations of trazodone alone or in combination with gabapentin in male cats

Trazodone and gabapentin are common oral sedatives in cats, used alone or combined, but no pharmacokinetic studies exist for trazodone in this species. The objective of this study was to determine the pharmacokinetics of oral trazodone (T) alone, or in combination with gabapentin (G) in healthy cats. Cats (n = 6) were randomly allocated to receive T (3 mg/kg) intravenously (IV), T (5 mg/kg) orally (PO), or T (5 mg/kg) and G (10 mg/kg) PO with a 1-week washout period between treatments. Heart rate, respiratory rate, indirect blood pressure, and level of sedation were assessed, and venous blood samples were collected serially over 24 h. Analysis of plasma trazodone concentration was performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Oral T administration resulted in a bioavailability of 54.9(7-96)%, and 17.2(11-25)% when administered with G. Tmax 0.17 (0.17-0.5) and 0.17 (0.17-0.75) h; Cmax 1.67 ± 0.91 and 1.22 ± 0.54 μg/mL, AUC 5.23 (2.0-18.76) and 2.37 (1.17-7.80) h*μg/mL; T1/2 5.12 ± 2.56 and 4.71 ± 1.07 h; for T and TG, respectively. Sedation was significant when compared to baseline in all groups from 20 or 45 min to 8 h indicating some lag between peak plasma concentration and sedative effects. Physiological variables remained within normal limits. This study concludes that oral trazodone is rapidly absorbed in healthy cats. Addition of gabapentin did not result in more profound sedation, showing no clinical advantage of combining these drugs in this study population.

Fear extinction in an obsessive-compulsive disorder animal model: Influence of sex and estrous cycle

Obsessive-compulsive disorder (OCD) is a neuropsychiatric condition that affects men and women equally, but with a sexually dimorphic pattern of development. Reproductive cycle events can influence symptom severity of OCD in females, indicating that ovarian hormones or their interaction with distinct neurotransmitter systems may play a role in OCD pathophysiology. Clinical studies and animal models have confirmed the importance of the serotonergic (5-HT) system in the neurobiology and treatment of OCD. Accordingly, the non-selective 5-HT2c agonist, meta-chlorophenylpiperazine (mCPP), exacerbates symptoms in untreated OCD patients. In rodents, it evokes repetitive behaviors that engage brain areas that are homologous with those found to be dysfunctional in OCD patients. These regions, including the medial prefrontal and anterior cingulate cortices, are also involved in fear inhibition, which is impaired in OCD. Here, we treated rats with mCPP (0.5 and 3.0 mg/kg) to evaluate its influence on self-grooming behavior and assess potential fear extinction retention deficits, taking into account sex differences and females' estrous cycle. We found that mCPP exacerbated grooming in male and female rats, irrespective of the estrous cycle phase. Fear extinction retention, however, was impaired only in females. Moreover, females undergoing fear extinction training during the metestrus/diestrus phases of the estrous cycle were more sensitive to the impairments induced by mCPP. Our results indicate that mCPP can induce OCD-like symptoms, exacerbating self-grooming and impairing fear extinction. It suggests that changes in 5-HT signaling through 5-HT2c receptors may have an important role in the OCD pathophysiology and that the influence of gonadal hormones in OCD should be further investigated.

Depressed suicidal adolescent males have an altered cortisol response to a pharmacological challenge

Dysregulation of the HPA axis and the dysfunction of the central serotonin (5HT) system are the most replicated biomarkers of depression and suicidal ideation and behavior. However, few studies have examined the two systems simultaneously. In this study, cortisol response was measured in depressed adolescents, following the administration of a central serotonin receptor agonist, meta-chlorphenylpiprazine (mCPP). Adolescents with major depression (MDD; n = 44; males = 15, females = 29; mean age ± SD = 15.5 ± 1.5) were divided into two groups: non-suicidal or those who reported passive suicidal ideation (n = 21), and those who had either threatened suicide or engaged in suicidal acts (n = 23). Sequential infusions of normal saline and mCPP were administered, and serial blood samples were collected for cortisol response. A differential time by group pattern of cortisol response following mCPP was found in the entire group (F(6,242) = 2.6, p=0.018). However, this was mostly attributed to males (F(6,73) = 2.3, p = 0.043) who had threatened or engaged in suicidal acts and displayed a higher cortisol response at 10 and 25 min after the infusion of mCPP, which was not affected by the severity of depression. This differential pattern of cortisol secretion in response to a serotonergic agonist may be a biomarker for more severe forms of suicidal ideation and behavior in adolescent males.

Pharmacology of ayahuasca administered in two repeated doses

RATIONALE

Ayahuasca is an Amazonian tea containing the natural psychedelic 5-HT(2A/2C/1A) agonist N,N-dimethyltryptamine (DMT). It is used in ceremonial contexts for its visionary properties. The human pharmacology of ayahuasca has been well characterized following its administration in single doses.

OBJECTIVES

To evaluate the human pharmacology of ayahuasca in repeated doses and assess the potential occurrence of acute tolerance or sensitization.

METHODS

In a double-blind, crossover, placebo-controlled clinical trial, nine experienced psychedelic drug users received PO the two following treatment combinations at least 1 week apart: (a) a lactose placebo and then, 4 h later, an ayahuasca dose; and (b) two ayahuasca doses 4 h apart. All ayahuasca doses were freeze-dried Amazonian-sourced tea encapsulated to a standardized 0.75 mg DMT/kg bodyweight. Subjective, neurophysiological, cardiovascular, autonomic, neuroendocrine, and cell immunity measures were obtained before and at regular time intervals until 12 h after first dose administration.

RESULTS

DMT plasma concentrations, scores in subjective and neurophysiological variables, and serum prolactin and cortisol were significantly higher after two consecutive doses. When effects were standardized by plasma DMT concentrations, no differences were observed for subjective, neurophysiological, autonomic, or immunological effects. However, we observed a trend to reduced systolic blood pressure and heart rate, and a significant decrease for growth hormone (GH) after the second ayahuasca dose.

CONCLUSIONS

Whereas there was no clear-cut tolerance or sensitization in the psychological sphere or most physiological variables, a trend to lower cardiovascular activation was observed, together with significant tolerance to GH secretion.

Current awareness of piperazines: pharmacology and toxicology

Although many piperazine derivatives exist, only a limited number have been studied, whereby they have been found to be generally stimulant in nature resulting from dopaminergic, noradrenergic, and predominantly serotoninergic effects in the brain. Reported toxic effects include agitation, anxiety, cardiac symptoms (e.g. tachycardia) and sometimes seizures. As for many drugs, they are primarily metabolized by cytochrome P450 with subsequent possible glucuronidation and/or sulfation. Their abuse has been relatively recently observed in the last decade with only a few identified in biological fluid (primarily 1-benzylpiperazine (BZP) and 1-(3-trifluoromethylphenyl)piperazine (3-TFMPP)) despite publications of a number of analytical methods. Even when detected, however, the toxicological significance of their presence is often difficult to ascertain as many cases involve other drugs as well as a wide and overlapping range of concentrations found in blood (both in life and after death). This paper reviews the current pharmacological and toxicological information for piperazine derivatives and also includes new ante-mortem and post-mortem blood data.

The autonomic stress-induced hyperthermia response is not enhanced by several anxiogenic drugs

While anxiety models are often based on locomotor activity responses, the stress-induced hyperthermia (SIH) paradigm uses the autonomic stress response by measuring body temperature. The effects of putative anxiogenic compounds in the SIH paradigm are inconclusive in mice and have not been examined in rats. Furthermore, it has been suggested that drug-induced effects on body temperature could be dependent on locomotor activity levels. Therefore, the effects of three anxiogenic substances, yohimbine (an α(2) receptor antagonist), mCPP (a 5HT(2C) receptor agonist) and FG-7142 (a GABA(A) receptor inverse agonist acting at the benzodiazepine site) on the stress-induced body temperature and locomotor activity response were studied in rats using novel cage stress. All anxiogenic compounds resulted in hypothermia. In contrast, FG-7142 and yohimbine increased locomotor activity levels, whereas mCPP reduced locomotor activity levels. The lack of an increased body temperature response of anxiogenic compounds indicates that the anxiogenic capacity of a drug does not necessarily yield increased autonomic stress responsivity. Moreover, the present study shows that a drug-induced decreased body temperature can be accompanied by increased locomotor activity, suggesting that both parameters represent independent parameters of the stress response.

Pharmacological management of appetite expression in obesity

For obese individuals, successful weight loss and maintenance are notoriously difficult. Traditional drug development fails to exploit knowledge of the psychological factors that crucially influence appetite, concentrating instead on restrictive criteria of intake and weight reduction, allied to a mechanistic view of energy regulation. Drugs are under development that may produce beneficial changes in appetite expression in the obese. These currently include glucagon-like peptide-1 analogs such as liraglutide, an amylin analog davalintide, the 5-HT(2C) receptor agonist lorcaserin, the monoamine re-uptake inhibitor tesofensine, and a number of combination therapies such as pramlintide and metreleptin, bupropion and naltrexone, phentermine and topiramate, and bupropion and zonisamide. However, the effects of these treatments on eating behavior remain poorly characterized. Obesity is typically a consequence of overconsumption driven by an individual's natural sensitivity to food stimuli and the pleasure derived from eating. Intuitively, these processes should be effective targets for pharmacotherapy, and behavioral analysis can identify drugs that selectively affect desire to eat, enjoyment of eating, satiation or postmeal satiety. Rational interventions designed specifically to modulate these processes could limit the normally aversive consequences of caloric restriction and maximize an individual's capacity to successfully gain control over their appetite.

Neuroendocrine and subjective responses to pharmacological challenge with citalopram: a controlled study in male and female ecstasy/MDMA users

Despite evidence that +/-3,4-methylenedioxymethamphetamine (MDMA; 'ecstasy') causes persistent alterations to the serotonergic system of animals, evidence for long-term neurological effects of ecstasy/MDMA in humans remains equivocal. The current study assessed serotonin functioning of nine male and 11 female recreational ecstasy polydrug users by measuring neuroendocrine (prolactin, cortisol) responses to pharmacological challenge with the selective serotonin reuptake inhibitor citalopram, compared with nine male and five female cannabis polydrug users and 11 male and 11 female non-drug using controls. A single-blind, randomised, placebo-controlled design was used. Subjective responses, other substance use, mood, personality traits and demographic variables were measured to control for potentially confounding variables. There were no significant differences between ecstasy polydrug users, cannabis polydrug users and non-drug using controls in neuroendocrine or subjective responses to serotonergic challenge, and there were no sex by drug group interactions. There was no relationship between extent of ecstasy use and neuroendocrine functioning, alone or in combination with potential confounding variables. Subjective responses to the pharmacological challenge (nausea, tremor, dry mouth), novelty seeking and lifetime dose of alcohol were the only variables that contributed to one or more of the neuroendocrine outcome variables. These data do not support the premise that recreational ecstasy/MDMA use results in measurable impairment of serotonergic control of endocrine activity.

Serotonergic drugs : effects on appetite expression and use for the treatment of obesity

Over 35 years of research suggests that endogenous hypothalamic serotonin (5-hydroxytryptamine) plays an important part in within-meal satiation and post-meal satiety processes. Thus, the serotonin system has provided a viable target for weight control, critical to the action of at least two effective anti-obesity treatments, both producing clinically significant weight loss over a year or more. Numerous serotonin receptor subtypes have been identified; of these, serotonin 5-HT1B and 5-HT2C receptors have been specifically recognised as mediators of serotonin-induced satiety.A number of serotonergic drugs, including selective serotonin reuptake inhibitors (SSRIs), dexfenfluramine and 5-HT2C receptor agonists, have been shown to significantly attenuate rodent bodyweight gain. This effect is strongly associated with marked hypophagia and is probably mediated by the hypothalamic melanocortin system. Additionally, sibutramine, dexfenfluramine, fluoxetine and the 5-HT2C receptor agonist chlorophenylpiperazine (mCPP) have all been shown to modify appetite in both lean and obese humans, resulting in reduced caloric intake. Clinical studies demonstrate serotonergic drugs specifically reduce appetite prior to and following the consumption of fixed caloric loads, and cause a reduction in pre-meal appetite and caloric intake at ad libitum meals. Weight loss in the obese has also been produced by treatment with both the serotonin precursor 5-hydroxytryptophan and the preferential 5-HT2C receptor agonist mCPP.A new generation of 5-HT2C receptor selective agonists have been developed and at least one, lorcaserin (APD356), is currently undergoing clinical trials. In addition, 5-HT6 receptor antagonists such as PRX-07034 and BVT74316 have been shown to potently reduce food intake and bodyweight gain in rodent models and have recently entered clinical trials. However, the role of the 5-HT6 receptor in the expression of appetite remains to be determined. The hope is that these drugs will not only be free of their predecessors' adverse effect profiles, but will also be equally or more effective at regulating appetite and controlling bodyweight.

La métachlorophénylpipérazine (mCPP) : une nouvelle drogue de synthèse

Metachlorophenylpiperazine (mCPP) is a psychoactive substance that appeared in 2004 on the black market of illicit substances in Europe and France. It has a strong affinity for serotoninergic receptors and the serotonin transporter. In humans, mCPP induces endocrine, neurological and psychiatric effects. Its subjective effects are similar to those of amphetamines. However, drug-users allot few positive subjective effects. Reported cases of intoxication are generally not serious but the risks of psychiatric disorders and serotoninergic syndrome must be taken into account. Risk factors of the intoxication to mCPP are the existence of predisposing psychiatric pathologies and pharmacodynamic or metabolic interactions. mCPP does not exhibit reinforcing effects. mCPP is not the subject of any international regulation: procedures of medical and social risk assessment were implemented in European and the national levels.

Functional magnetic resonance imaging and c-Fos mapping in rats following an anorectic dose of m-chlorophenylpiperazine

We have used blood-oxygenation-level-dependent (BOLD) contrast functional magnetic resonance imaging (fMRI) to characterise brain regions responsive to a regulator of appetite. An anorectic dose of the 5-HT(1B/2C) receptor agonist m-chlorophenylpiperazine (mCPP; 3 mg/kg s.c.) was used to compare BOLD contrast fMRI with expression of the c-Fos protein. mCPP was administered to rats, which were then anaesthetised and perfused with fixative 90 min later to allow immunohistochemistry. In a separate experiment, rats were imaged using a T(2)*-weighted gradient echo in a 7 T magnet for 70 min under alpha-chloralose anaesthesia. Both methods detected positive activation in areas of the limbic system: cingulate and orbitofrontal cortices, nucleus accumbens, paraventricular and dorsomedial regions of the hypothalamus. fMRI detected increased signal in the pontine nuclei, the hippocampal formation and olfactory cortex, areas that did not display c-Fos. In addition, BOLD signal was diminished in the ventral tegmental area, preoptic area and the cerebellum-presumably due to decreased neuronal signalling and, therefore, unlikely to display c-Fos. Activity in the limbic system may reflect the appetitive agonist activity of mCPP at the 5-HT(2C) receptor. We conclude that c-Fos provides excellent spatial information but is less useful for detecting inhibited regions, whereas fMRI provides greater temporal resolution. Thus, the two methodologies provide complementary details of brain activity following pharmacological challenge.

Methylone and mCPP, two new drugs of abuse?

Recently, two new ecstasy-like substances, methylone and mCPP, were found in street drugs in the Netherlands by the Drugs Information and Monitoring System (DIMS). Methylone (3,4-methylenedioxymethcathinone) is the main ingredient of a new liquid designer drug that appeared on the Dutch drug market, called 'Explosion'. mCPP (meta-chlorophenylpiperazine) is a substance often used as a probe for the serotonin function in psychiatric research, and has now been found in street drugs, both in tablets and powders. Methylone as well as mCPP act on monoaminergic systems, resembling MDMA (3,4-methylenedioxymethamphetamine), with mCPP mainly affecting the serotonin system. The subjective effects of both new substances exhibit subtle differences with those of MDMA. Only little is known about the harmfulness of both methylone and mCPP. However, because of similarities between these substances and MDMA, risks common to MDMA cannot be excluded.

Comparison of the effects of citalopram and escitalopram on 5-Ht-mediated neuroendocrine responses

Acute oral administration of selective serotonin re-uptake inhibitors (SSRIs) increases plasma cortisol by facilitating brain serotonin activity. Recently, salivary cortisol sampling has grown in popularity as a noninvasive means of assessing HPA axis activity. The aim of the present study was to find out whether acute oral administration of the SSRI, citalopram, increases salivary cortisol in healthy volunteers and whether the increase produced by an equivalent dose of its active isomer, escitalopram, is greater. A total of 15 healthy subjects were tested on three occasions receiving either oral citalopram (20 mg), escitalopram (10 mg), or placebo in a double-blind, randomized, crossover design. Salivary cortisol and plasma cortisol and prolactin were measured for 240 min after each treatment. Relative to placebo, both citalopram and escitalopram increased salivary and plasma cortisol levels with no evidence of consistent differences between them. Plasma prolactin concentration was not altered by either active treatment. Plasma and salivary cortisol responses after citalopram but not escitalopram correlated significantly. The present study does not support an enhanced effect of escitalopram on 5-HT-mediated neuroendocrine responses.