Sprague-Dawley rats display sex-linked differences in the pharmacokinetics of 3,4-methylenedioxymethamphetamine (MDMA) and its metabolite 3,4-methylenedioxyamphetamine (MDA)

Recreational MDMA doses do not elicit hepatotoxicity in HepG2 spheroids under normo- and hyperthermia

MDMA (3,4-methylenedioxymethamphetamine), an entactogen with empathogenic and prosocial effects, is widely used in music festivals and other festive settings. High MDMA doses have been associated with drug-induced liver injury and cases of hyperthermia. Although the latter condition is thought to increase MDMA hepatotoxicity, this correlation remains poorly explored for recreational MDMA doses. On the other hand, the fact that MDMA acts to extinguish fear and to reconsolidate memory could be explored as an adjunct to psychotherapy during treatment of neuropsychiatric disorders such as post-traumatic stress disorder. In this context, assessing MDMA toxicity is relevant, and tridimensional cell culture has emerged as an alternative to animal models in toxicity assessment. Herein, we have used HepG2 spheroids to evaluate MDMA-induced hepatotoxicity at recreational doses, under normo- or hyperthermia. The MTT reduction assay did not evidence significantly reduced cell viability. Moreover, MDMA did not increase reactive oxygen species production, deplete the mitochondrial membrane potential, arrest the cell cycle, or induce apoptotic cell death. These findings support further pre-clinical investigation of MDMA safety from the perspective of both harm reduction and therapy given that non-abusive recreational and therapeutic doses overlap.

Does MDMA have treatment potential in sexual dysfunction? A systematic review of outcomes across the female and male sexual response cycles

INTRODUCTION

Sexual health, an integral component of overall well-being, is frequently compromised by common yet underdiagnosed sexual dysfunctions. Traditional interventions encompass pharmaceutical and psychological treatments. Unconventional therapies, like MDMA, offer hope for sexual dysfunction. This review delves into MDMA's effects on sexual responsiveness and its potential role in treating sexual dysfunction.

OBJECTIVES

The purpose of this review is to elucidate effects of MDMA on different domains of the female and male sexual response cycles.

METHODS

We conducted a systematic review on the effects of MDMA on each domain of the female and male sexual response cycles. PubMed, MEDLINE, and EMBASE were queried, and results were screened using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Search terms utilized were "MDMA" or "ecstasy" in combination with "desire," "arousal," "lubrication," "orgasm," "pleasure," "libido," "erection," and "ejaculation." Inclusion criteria for this review were MDMA use by study subjects and sexual outcomes in at least 1 domain of the female and/or male sexual response cycles were described and measured. Randomized controlled trials, cohort studies (both prospective and retrospective), surveys, and literature reviews published between January 2000 and June 2022 were included. Case reports and studies that did not address conditions of interest were excluded from analysis. Duplicated search results were screened out. The remaining studies were then read in full text to ensure they met inclusion and exclusion criteria for analysis.

RESULTS

We identified 181 studies, of which 6 met criteria for assessment of the female sexual response cycle and 8 met criteria for assessment of the male sexual response cycle. Four of 6 studies reported increased sexual desire with MDMA use among women. Arousal and lubrication were improved with MDMA use in 3 of 4 studies, but they were not affected in 1 randomized control study. In men, 7 studies evaluated the effects of MDMA on desire and/or arousal, 5 studies measured impact on erection, 3 on orgasm, and 2 on ejaculation. Sixty percent of interview-based studies reported increased sexual desire in men, while 40% reported mixed or no effect. Two studies reported impairment of erection, 2 reported mixed effects, and 1 reported fear of erection impairment. In both men and women, all studies evaluating orgasm reported delay in achieving orgasm but increased intensity and pleasure if achieved. Primary outcome measures were variable and largely qualitative.

CONCLUSION

Our findings suggest that MDMA generally increases sexual desire and intensifies orgasm when achieved. While producing conflicting evidence on sexual arousal in both sexes, MDMA may impair erectile and ejaculatory function in men.

Women and MDMA: particularities of gender and sex

This comprehensive review delves into the intricate interplay between gender/sex and MDMA use, drawing upon recent evidence. It explores how girls, as a means of coping with negative emotions, often resort to drug use, while boys primarily initiate drug use due to peer pressure or sensation-seeking tendencies. Women, frequently having endured traumatic life events, may turn to MDMA as a form of self-medication. Notably, women face an elevated risk of contracting sexually transmitted infections due to their altered mental states and diminished condom use during MDMA consumption. Additionally, females exhibit heightened sensitivity to the subjective effects of MDMA, consistently reporting heightened anxiety, adverse effects, and negative side effects. While women may have a higher susceptibility to hyponatremia, intriguingly, they appear to be less vulnerable to MDMA-induced hyperthermia. Although limited, available data suggest that prenatal MDMA exposure could lead to motor delays in infants, necessitating further research to unravel the potential cognitive effects. Furthermore, MDMA-assisted psychotherapy holds immense promise for addressing post-traumatic stress disorder (PTSD) among female subgroups. These pronounced gender and sex disparities in MDMA use and its effects underscore the pressing need for additional research to develop tailored, effective, and safe treatment approaches that account for these fundamental factors.

Neurochemical and Behavioral Profiling in Male and Female Rats of the Psychedelic Agent 25I-NBOMe

4-Iodo-2,5-dimethoxy-N-(2-methoxybenzyl)phenethylamine (25I-NBOMe), commonly called “N-Bomb,” is a synthetic phenethylamine with psychedelic and entactogenic effects; it was available on the Internet both as a legal alternative to lysergic acid diethylamide (LSD) and as a surrogate of 3,4-methylenedioxy-methamphetamine (MDMA), but now it has been scheduled among controlled substances. 25I-NBOMe acts as full agonist on serotonergic 5-HT2A receptors. Users are often unaware of ingesting fake LSD, and several cases of intoxication and fatalities have been reported. In humans, overdoses of “N-Bomb” can cause tachycardia, hypertension, seizures, and agitation. Preclinical studies have not yet widely investigated the rewarding properties and behavioral effects of this compound in both sexes. Therefore, by in vivo microdialysis, we evaluated the effects of 25I-NBOMe on dopaminergic (DA) and serotonergic (5-HT) transmissions in the nucleus accumbens (NAc) shell and core, and the medial prefrontal cortex (mPFC) of male and female rats. Moreover, we investigated the effect of 25I-NBOMe on sensorimotor modifications as well as body temperature, nociception, and startle/prepulse inhibition (PPI). We showed that administration of 25I-NBOMe affects DA transmission in the NAc shell in both sexes, although showing different patterns; moreover, this compound causes impaired visual responses in both sexes, whereas core temperature is heavily affected in females, and the highest dose tested exerts an analgesic effect prominent in male rats. Indeed, this drug is able to impair the startle amplitude with the same extent in both sexes and inhibits the PPI in male and female rats. Our study fills the gap of knowledge on the behavioral effects of 25I-NBOMe and the risks associated with its ingestion; it focuses the attention on sex differences that might be useful to understand the trend of consumption as well as to recognize and treat intoxication and overdose symptoms.

A review of the influence of functional group modifications to the core scaffold of synthetic cathinones on drug pharmacokinetics

RATIONALE

The synthetic cathinones are a class of designer drugs of abuse that share a common core scaffold. The pharmacokinetic profiles of the synthetic cathinones vary based on the substitutions to the core scaffold.

OBJECTIVES

To provide a summary of the literature regarding the pharmacokinetic characteristics of the synthetic cathinones, with a focus on the impact of the structural modifications to the pharmacokinetics.

RESULTS

In many, but not all, instances the pharmacokinetic characteristics of the synthetic cathinones can be reasonably predicted based on the substitutions to the core scaffold. Mephedrone and methylone are chemically alike and have similar T_max and t_1/2 in male rats. MDPV, a structurally distinct synthetic cathinone from mephedrone and methylone, has a lower T_max and t_1/2. Increasing the length of the alkyl chain on the α position of methylone, to produce pentylone, results in increased plasma concentrations and longer t_1/2. Metabolism of the synthetic cathinones is reasonably predictable based on the chemical structure, and several phase I metabolites retain pharmacodynamic activity. CYP2D6 is implicated in the metabolism of all of the synthetic cathinones, and other P450s (CYP1A2, CYP2B6, and CYP2C19) are known to contribute variably to the metabolism of specific synthetic cathinones.

CONCLUSIONS

Continued research will lead to a better understanding of the pharmacokinetic changes associated with structural modifications to the cathinone scaffold, and potentially in the long range, enhanced overdose and addiction therapy. Additionally, the areas of polydrug use and pharmacogenetics have been largely overlooked with regard to synthetic cathinones.

Evaluation of the Ecstasy influence on tramadol and its main metabolite plasma concentration in rats

BACKGROUND

Tramadol is prone to be abused alone, or in combination with 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy). It was reported that 95% of people with a history of substance abuse in the United States used tramadol in 2004. According to the WHO report in 2016, there was a growing number of tramadol abusers alone or in combination with psychoactive substances such as MDMA in particular in some Middle East countries. Higher concentrations of tramadol in plasma may lead to adverse drug reactions or lethal intoxication. In this study, the effect of MDMA on the pharmacokinetics of tramadol was examined in male rats.

METHODS

The effect of MDMA on Tmax, Cmax, area under the curve, elimination rate, and half-life of tramadol and its metabolites was examined. Two control and two treatment groups were designed. The treatment groups received MDMA 18 h before the administration of tramadol. Jugular vein blood samples were analyzed by high-performance liquid chromatography with fluorescent detector to determine the concentrations of tramadol and its metabolites. Independent-sample t-test was used to define the differences between pharmacokinetic parameters of control and treatment groups.

RESULTS

When tramadol administered intraperitoneally, the absorption rate of this drug was reduced, and a lower Cmax (40%) with longer Tmax (eight-fold) was achieved. MDMA exerted greater inhibitory effects on cytochrome P450 3A4 (CYP3A4) than on cytochrome P450 2D6 (CYP2D6). The M2 metabolite ratio was reduced by half, and because of the inhibition of M2 production, the M1 plasma concentration slightly increased.

CONCLUSIONS

According to the obtained data, MDMA treatment affected the absorption, distribution and metabolism phases of tramadol. This treatment increased the concentration of tramadol if administered intravenously and can latent the absorption of tramadol in oral route. However, MDMA was introduced as CYP2D6 inhibitor; in this study, MDMA inhibited CYP3A4 isoenzymes as well. This finding is important for the compounds that are metabolized through CYP3A4. It can be proposed that in abusers of MDMA who only receive tramadol for medical or nonmedical purposes in short intervals, the dangers of the intravenous administration of tramadol should be considered, and if tramadol is administered orally, the desired effect may not be achieved at the routine dose.

Sex differences in abuse-related neurochemical and behavioral effects of 3,4-methylenedioxymethamphetamine (MDMA) in rats

3,4-Methylenedioxymethamphetamine (MDMA) is a substrate for dopamine (DA), norepinephrine and serotonin (5HT) transporters that produces greater pharmacological effects on certain endpoints in females than males in both clinical and rodent preclinical studies. To evaluate potential for sex differences in abuse-related MDMA effects, the present study compared MDMA effects on intracranial self-stimulation (ICSS) and on in vivo microdialysis measurements of DA or 5HT in the nucleus accumbens (NAc) in female and male Sprague-Dawley rats. For ICSS studies, electrodes were implanted in the medial forebrain bundle and rats trained to press for electrical stimulation over a range of frequencies (56-158Hz, 0.05 log increments) under a fixed-ratio 1 schedule, and the potency (0.32-3.2mg/kg, 10min pretreatment) and time course (3.2. mg/kg, 10-180min pretreatment) of MDMA effects were determined. For in vivo microdialysis, rats were implanted with bilateral guide cannulae targeting the NAc, and the time course of MDMA effects (1.0-3.2mg/kg, 0-180min) on DA and 5HT was determined. MDMA produced qualitatively similar effects in both sexes on ICSS (both increases in low ICSS rates maintained by low brain-stimulation frequencies and decreases in high ICSS rates maintained by high brain-stimulation frequencies) and microdialysis (increases in both DA and 5HT). The duration and peak levels of both abuse-related ICSS facilitation and increases in NAc DA were longer in females. MDMA was also more potent to increase 5HT in females. These results provide evidence for heightened sensitivity of females to abuse-related behavioral and neurochemical effects of MDMA in rats.

MDMA Impairs Response to Water Intake in Healthy Volunteers

Hyponatremia is a serious complication of 3,4-methylenedioxymethamphetamine (MDMA) use. We investigated potential mechanisms in two double-blind, placebo-controlled studies. In Study 1, healthy drug-experienced volunteers received MDMA or placebo alone and in combination with the alpha-1 adrenergic inverse agonist prazosin, used as a positive control to release antidiuretic hormone (ADH). In Study 2, volunteers received MDMA or placebo followed by standardized water intake. MDMA lowered serum sodium but did not increase ADH or copeptin, although the control prazosin did increase ADH. Water loading reduced serum sodium more after MDMA than after placebo. There was a trend for women to have lower baseline serum sodium than men, but there were no significant interactions with drug condition. Combining studies, MDMA potentiated the ability of water to lower serum sodium. Thus, hyponatremia appears to be a significant risk when hypotonic fluids are consumed during MDMA use. Clinical trials and events where MDMA use is common should anticipate and mitigate this risk.

Gender-Dependent Pharmacokinetics of Veratramine in Rats: In Vivo and In Vitro Evidence

Veratramine, a major alkaloid from Veratrum nigrum L., has distinct anti-tumor and anti-hypertension effects. Our previous study indicated that veratramine had severe toxicity toward male rats. In order to elucidate the underling mechanism, in vivo pharmacokinetic experiments and in vitro mechanistic studies have been conducted. Veratramine was administrated to male and female rats intravenously via the jugular vein at a dose of 50 μg/kg or orally via gavage at 20 mg/kg. As a result, significant pharmacokinetic differences were observed between male and female rats after oral administration with much lower concentrations of veratramine and 7-hydroxyl-veratramine and higher concentrations of veratramine-3-O-sulfate found in the plasma and urine of female rats. The absolute bioavailability of veratramine was 0.9% in female rats and 22.5% in male rats. Further experiments of veratramine on Caco-2 cell monolayer model and in vitro incubation with GI content or rat intestinal subcellular fractions demonstrated that its efficient passive diffusion mediated absorption with minimal intestinal metabolism, suggesting no gender-related difference during its absorption process. When veratramine was incubated with male or female rat liver microsomes/cytosols, significant male-predominant formation of 7-hydroxyl-veratramine and female-predominant formation of veratramine-3-O-sulfate were observed. In conclusion, the significant gender-dependent hepatic metabolism of veratramine could be the major contributor to its gender-dependent pharmacokinetics.

Effects of 3,4-methylenedioxymethamphetamine (MDMA) and its main metabolites on cardiovascular function in conscious rats

BACKGROUND AND PURPOSE

The cardiovascular effects produced by 3,4-methylenedioxymethamphetamine (MDMA; 'Ecstasy') contribute to its acute toxicity, but the potential role of its metabolites in these cardiovascular effects is not known. Here we examined the effects of MDMA metabolites on cardiovascular function in rats.

EXPERIMENTAL APPROACH

Radiotelemetry was employed to evaluate the effects of s.c. administration of racemic MDMA and its phase I metabolites on BP, heart rate (HR) and locomotor activity in conscious male rats.

KEY RESULTS

MDMA (1-20 mg·kg(-1)) produced dose-related increases in BP, HR and activity. The peak effects on HR occurred at a lower dose than peak effects on BP or activity. The N-demethylated metabolite, 3,4-methylenedioxyamphetamine (MDA), produced effects that mimicked those of MDMA. The metabolite 3,4-dihydroxymethamphetamine (HHMA; 1-10 mg·kg(-1)) increased HR more potently and to a greater extent than MDMA, whereas 3,4-dihydroxyamphetamine (HHA) increased HR, but to a lesser extent than HHMA. Neither dihydroxy metabolite altered motor activity. The metabolites 4-hydroxy-3-methoxymethamphetamine (HMMA) and 4-hydroxy-3-methoxyamphetamine (HMA) did not affect any of the parameters measured. The tachycardia produced by MDMA and HHMA was blocked by the β-adrenoceptor antagonist propranolol.

CONCLUSIONS AND IMPLICATIONS

Our results demonstrate that HHMA may contribute significantly to the cardiovascular effects of MDMA in vivo. As such, determining the molecular mechanism of action of HHMA and the other hydroxyl metabolites of MDMA warrants further study.

Mephedrone and other cathinones

PURPOSE OF REVIEW

New designer drugs are constantly emerging in the illicit drug market and represent a significant health problem. A very popular class comprises synthetic cathinones, β-keto amphetamine analogues, endowed with psychostimulant properties. The aim of this review is to discuss the recent progress in our understanding of how cathinones act and the health consequences of their use.

RECENT FINDINGS

Despite being banned, synthetic cathinones are still used, especially by certain sub-populations. The recently observed trend to supplement psychostimulatory drugs of abuse with mephedrone must be considered highly dangerous to the public health. At the molecular level, the drugs act as blockers or substrates for monoamine transporter proteins. In animal studies, cathinones were found to evoke abuse-related behaviors and to have a negative impact on cognitive processes. The increased popularity of mephedrone among men who have sex with men with alarming sexual health consequences warrants the implementation of new treatments and education/training programs.

SUMMARY

Synthetic cathinones exert similar, but not identical, effects to psychostimulatory drugs of abuse. The use of cathinones may lead to serious psychotic, neurological, cardiovascular, and sexual health consequences. Exposure to these drugs may result in multiorgan failure and death.

Adolescent MDMA exposure diminishes the physiological and neurotoxic consequences of an MDMA binge in female rats

Intermittent MDMA pretreatment blocked the reductions in serotonin transporter (SERT) binding induced by an MDMA binge in a prior study in adolescent male rats. The objective of this investigation was to determine if the physiological, behavioral, and neurochemical responses to MDMA are sexually dimorphic. Female Sprague-Dawley rats received MDMA (10 mg/kg × 2) or Saline on every fifth day from postnatal day (PD) 35-60 and an MDMA binge (5 mg/kg × 4) on PD 67. The MDMA binge induced a pronounced temperature dysregulation in MDMA-naïve, but not MDMA-pretreated, groups. Similarly, MDMA-pretreated animals were resistant to the binge-induced SERT reductions, especially in the hippocampus. Motor activity at PD 68 was not reduced by the binge, unlike the responses found in males. These results show that female rats differ from males in their responses to an MDMA binge but are similar with respect to preconditioning from prior MDMA exposure.

Sex-dependent long-term effects of adolescent exposure to THC and/or MDMA on neuroinflammation and serotoninergic and cannabinoid systems in rats

BACKGROUND AND PURPOSE

Many young people consume ecstasy as a recreational drug and often in combination with cannabis. In this study, we aimed to mimic human consumption patterns and investigated, in male and female animals, the long-term effects of Δ(9) -tetrahydrocannabinol (THC) and 3,4-methylenedioxymethamphetamine (MDMA) on diverse neuroinflammation and neurotoxic markers.

EXPERIMENTAL APPROACH

Male and female Wistar rats were chronically treated with increasing doses of THC and/or MDMA during adolescence. The effects of THC and/or MDMA on glial reactivity and on serotoninergic and cannabinoid systems were assessed by immunohistochemistry in the hippocampus and parietal cortex.

KEY RESULTS

THC increased the area staining for glial fibrilar acidic protein in both sexes. In males, both drugs, either separately or in combination, increased the proportion of reactive microglia cells [ionized calcium binding adaptor molecule 1 (Iba-1)]. In contrast, in females, each drug, administered alone, decreased of this proportion, whereas the combination of both drugs resulted in a 'normalization' to control values. In males, MDMA reduced the number of SERT positive fibres, THC induced the opposite effect and the group receiving both drugs did not significantly differ from the controls. In females, MDMA reduced the number of SERT positive fibres and the combination of both drugs counteracted this effect. THC also reduced immunostaining for CB1 receptors in females and this effect was aggravated by the combination with MDMA.

CONCLUSIONS AND IMPLICATIONS

Adolescent exposure of rats to THC and/or MDMA induced long-term, sex-dependent neurochemical and glial alterations, and revealed interactions between the two drugs.

LINKED ARTICLES

This article is part of a themed section on Cannabinoids 2013. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-6.

Mephedrone pharmacokinetics after intravenous and oral administration in rats: relation to pharmacodynamics

RATIONALE

Mephedrone (4-methylmethcathinone) is a still poorly known drug of abuse, alternative to ecstasy or cocaine.

OBJECTIVE

The major aims were to investigate the pharmacokinetics and locomotor activity of mephedrone in rats and provide a pharmacokinetic/pharmacodynamic model.

METHODS

Mephedrone was administered to male Sprague-Dawley rats intravenously (10 mg/kg) and orally (30 and 60 mg/kg). Plasma concentrations and metabolites were characterized using LC/MS and LC-MS/MS fragmentation patterns. Locomotor activity was monitored for 180-240 min.

RESULTS

Mephedrone plasma concentrations after i.v. administration fit a two-compartment model (α = 10.23 h(-1), β = 1.86 h(-1)). After oral administration, peak mephedrone concentrations were achieved between 0.5 and 1 h and declined to undetectable levels at 9 h. The absolute bioavailability of mephedrone was about 10% and the percentage of mephedrone protein binding was 21.59 ± 3.67%. We have identified five phase I metabolites in rat blood after oral administration. The relationship between brain levels and free plasma concentration was 1.85 ± 0.08. Mephedrone induced a dose-dependent increase in locomotor activity, which lasted up to 2 h. The pharmacokinetic-pharmacodynamic model successfully describes the relationship between mephedrone plasma concentrations and its psychostimulant effect.

CONCLUSIONS

We suggest a very important first-pass effect for mephedrone after oral administration and an easy access to the central nervous system. The model described might be useful in the estimation and prediction of the onset, magnitude, and time course of mephedrone pharmacodynamics as well as to design new animal models of mephedrone addiction and toxicity.

Disruption of prepulse inhibition by 3,4-methylenedioxymethamphetamine (MDMA): comparison between male and female wild-type and 5-HT(1A) receptor knockout mice

The aim of this study was to investigate the involvement of serotonin-1A (5-HT(1A)) receptors in the effects of 3,4-methylenedioxymetamphetamine (MDMA) on prepulse inhibition of acoustic startle (PPI) by comparing male and female wild-type (WT) mice and 5-HT(1A) receptor knockout (1AKO) mice. MDMA dose-dependently decreased PPI in male and female mice although female mice were more sensitive at the 100-ms inter-stimulus interval (ISI). In male mice, 10 mg/kg MDMA disrupted PPI in 1AKO but not in WT controls. There was no genotype difference at higher or lower doses of MDMA. In female mice, there was no difference between genotypes at any dose of MDMA. Average startle was reduced by 10 mg/kg and 20 mg/kg MDMA similarly in male and female mice and all genotypes. These results show an involvement of 5-HT(1A) receptors in the effect of MDMA on PPI in male, but not female mice.

Population pharmacokinetics of 3,4-methylenedioxymethamphetamine and main metabolites in rats

The pharmacokinetics of the recreational drug 3,4-methylenedioxymethamphetamine (MDMA) and its mains metabolites have never been modeled together. We therefore designed a model with which to analyze the pharmacokinetics of MDMA, 3,4-methylenedioxyamphetamine (MDA), 4-hydroxy-3-methoxymethamphetamine (HMMA), and 4-hydroxy-3-methoxyamphetamine (HMA) and to test the effect of covariates like gender and body weight on the pharmacokinetics. Rats (18 males and 18 females) were given 1 mg/kg MDMA iv, and the concentrations of MDMA, MDA, and HMMA were measured by high-performance liquid chromatography-mass spectrometry. Another 30 rats (15 males) were given 1 mg/kg MDA, and MDA and HMA were measured. A population pharmacokinetic model was developed to describe the changes in MDMA, HMMA, MDA, and HMA concentrations over time and to estimate interanimal variability. The influence of gender was tested using a likelihood ratio test. Estimated exposures of males and females to MDMA and its metabolites were compared using the Wilcoxon nonparametric test. An integrated six-compartment model adequately described the data. MDMA (two compartments) was transformed irreversible to HMMA (one compartment) and MDA (two compartments), which then produced HMA (one compartment). All rate constants were first order. Females given MDMA had significantly smaller MDMA distribution volumes than males, and they converted less MDMA to MDA than did males. Our MDMA, MDA, HMA, and HMMA model is suitable for examining the relationship between drug concentrations and its pharmacological/toxicological effects. Male rats were exposed to significantly more MDA and HMA than were females, which could explain why males are more sensitive to MDMA toxic effects than females.