1
|
Maher EE, Strzelecki AM, Weafer JJ, Gipson CD. The importance of translationally evaluating steroid hormone contributions to substance use. Front Neuroendocrinol 2023; 69:101059. [PMID: 36758769 PMCID: PMC10182261 DOI: 10.1016/j.yfrne.2023.101059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 01/22/2023] [Accepted: 02/03/2023] [Indexed: 02/10/2023]
Abstract
Clinically, women appear to be more susceptible to certain aspects of substance use disorders (SUDs). The steroid hormones 17β-estradiol (E2) and progesterone (Pg) have been linked to women-specific drug behaviors. Here, we review clinical and preclinical studies investigating how cycling ovarian hormones affect nicotine-, cocaine-, and opioid-related behaviors. We also highlight gaps in the literature regarding how synthetic steroid hormone use may influence drug-related behaviors. In addition, we explore how E2 and Pg are known to interact in brain reward pathways and provide evidence of how these interactions may influence drug-related behaviors. The synthesis of this review demonstrates the critical need to study women-specific factors that may influence aspects of SUDs, which may play important roles in addiction processes in a sex-specific fashion. It is important to understand factors that impact women's health and may be key to moving the field forward toward more efficacious and individualized treatment strategies.
Collapse
Affiliation(s)
- Erin E Maher
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, United States
| | - Ashley M Strzelecki
- Department of Psychology, University of Kentucky, Lexington, KY, United States
| | - Jessica J Weafer
- Department of Psychology, University of Kentucky, Lexington, KY, United States
| | - Cassandra D Gipson
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, United States.
| |
Collapse
|
2
|
Hilz EN, Lee HJ. Estradiol and progesterone in female reward-learning, addiction, and therapeutic interventions. Front Neuroendocrinol 2023; 68:101043. [PMID: 36356909 DOI: 10.1016/j.yfrne.2022.101043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 09/24/2022] [Accepted: 10/28/2022] [Indexed: 11/09/2022]
Abstract
Sex steroid hormones like estradiol (E2) and progesterone (P4) guide the sexual organization and activation of the developing brain and control female reproductive behavior throughout the lifecycle; importantly, these hormones modulate functional activity of not just the endocrine system, but most of the nervous system including the brain reward system. The effects of E2 and P4 can be seen in the processing of and memory for rewarding stimuli and in the development of compulsive reward-seeking behaviors like those seen in substance use disorders. Women are at increased risk of developing substance use disorders; however, the origins of this sex difference are not well understood and therapeutic interventions targeting ovarian hormones have produced conflicting results. This article reviews the contribution of the E2 and P4 in females to functional modulation of the brain reward system, their possible roles in origins of addiction vulnerability, and the development and treatment of compulsive reward-seeking behaviors.
Collapse
Affiliation(s)
- Emily N Hilz
- The University of Texas at Austin, Department of Pharmacology, USA.
| | - Hongjoo J Lee
- The University of Texas at Austin, Department of Psychology, USA; The University of Texas at Austin, Institute for Neuroscience, USA
| |
Collapse
|
3
|
Peart DR, Andrade AK, Logan CN, Knackstedt LA, Murray JE. Regulation of Cocaine-related Behaviors by Estrogen and Progesterone. Neurosci Biobehav Rev 2022; 135:104584. [DOI: 10.1016/j.neubiorev.2022.104584] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 01/30/2022] [Accepted: 02/12/2022] [Indexed: 10/19/2022]
|
4
|
McNealy KR, Houser SD, Barrett ST, Bevins RA. Investigating sex differences and the effect of drug exposure order in the sensory reward-enhancing effects of nicotine and d-amphetamine alone and in combination. Neuropharmacology 2022; 202:108845. [PMID: 34678376 PMCID: PMC8627442 DOI: 10.1016/j.neuropharm.2021.108845] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 09/30/2021] [Accepted: 10/15/2021] [Indexed: 01/03/2023]
Abstract
Nicotine enhances the rewarding effects of other environmental stimuli; this reward-enhancement encourages and maintains nicotine consumption. Nicotine use precedes other psychostimulant use, but receiving a stimulant prescription also predicts future smoking. Previously, no study has investigated effects of drug exposure order in reward-enhancement, nor with nicotine and d-amphetamine. Thus, we aimed to investigate how drug exposure order impacted the reward-enhancing effects of nicotine and d-amphetamine, alone and in combination. We used 20 male and 20 female Sprague-Dawley rats. Enhancement was investigated within-subjects by examining responding maintained by a visual stimulus reinforcer following a pre-session injection of either d-amphetamine (Sal, 0.1, 0.3, or 0.6 mg/kg) or nicotine (Sal, 0.03, 0.06, 0.1, 0.3 mg/kg). Twenty rats (10 M, 10 F) completed enhancement testing with nicotine before d-amphetamine. The other 20 rats (10 M, 10 F) completed testing with d-amphetamine before nicotine. Following these phases, rats were then given two pre-session injections: one of d-amphetamine (Sal, 0.1, 0.3, or 0.6 mg/kg) and another of nicotine (Sal, 0.03, 0.06, 0.1, or 0.3 mg/kg). Experiencing amphetamine before nicotine increased reward-enhancing effects of nicotine. Females exhibited greater effects of d-amphetamine on reward-enhancement, with no effect of exposure order. During the interaction phase, receiving nicotine before amphetamine enhanced the interaction between nicotine and d-amphetamine for females whereas amphetamine before nicotine heightened this interaction for males. From this, prior and current amphetamine use, in addition to sex, should be considered when treating nicotine dependency and when examining factors driving poly-substance use involving nicotine and d-amphetamine. Keywords: Adderall, ADHD, Dexedrine, operant, smoking, polysubstance use.
Collapse
Affiliation(s)
- Kathleen R McNealy
- Department of Psychology University of Nebraska-Lincoln, 238 Burnett Hall, Lincoln, NE, 68588-0308, USA
| | - Sydney D Houser
- Department of Psychology University of Nebraska-Lincoln, 238 Burnett Hall, Lincoln, NE, 68588-0308, USA
| | - Scott T Barrett
- Department of Psychology University of Nebraska-Lincoln, 238 Burnett Hall, Lincoln, NE, 68588-0308, USA
| | - Rick A Bevins
- Department of Psychology University of Nebraska-Lincoln, 238 Burnett Hall, Lincoln, NE, 68588-0308, USA.
| |
Collapse
|
5
|
McNealy KR, Ramsay ME, Barrett ST, Bevins RA. Reward-enhancing effects of d-amphetamine and its interactions with nicotine were greater in female rats and persisted across schedules of reinforcement. Behav Pharmacol 2021; 32:435-447. [PMID: 34010168 PMCID: PMC8266728 DOI: 10.1097/fbp.0000000000000637] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Nicotine enhances the value of environmental stimuli and rewards, and reward enhancement can maintain nicotine consumption. Stimulants such as d-amphetamine are misused more by women and are commonly co-used with nicotine. d-Amphetamine potentiates nicotine's effects in human and animal research. To date, there are no published studies examining this interaction in a reward-enhancement task. The current study sought to investigate the reward-enhancing effects of nicotine alongside and coadministered with d-amphetamine. Further, we evaluated the persistence of reward enhancement across ratio and temporal schedules of reinforcement. We used 10 male and 10 female Sprague-Dawley rats. Enhancement was assessed within subjects by examining active lever pressing for a visual stimulus reinforcer on variable ratio 3, variable interval 30 s and variable time 30 s - variable ratio 3 schedules. Before 1-h sessions, rats received one injection of saline, 0.1 or 0.3 mg/kg d-amphetamine and one of saline or 0.4 mg/kg nicotine, making six possible drug combinations (saline + saline, saline + nicotine, 0.1 d-amphetamine + aline, 0.1 d-amphetamine + nicotine, 0.3 d-amphetamine + saline and 0.3 d-amphetamine + nicotine) experienced in a randomized order by each rat. When d-amphetamine was coadministered with nicotine, we found an interaction effect on reward enhancement that persisted across schedules of reinforcement. Males and females exhibited reward enhancement by 0.3 d-amphetamine, while only females showed reward enhancement by 0.1 d-amphetamine. Further, females responded more for the visual stimulus than males in all d-amphetamine conditions. Future studies should assess how reward enhancement is involved in high nicotine-amphetamine comorbidity rates and enhanced amphetamine misuse in women.
Collapse
Affiliation(s)
- Kathleen R McNealy
- Department of Psychology, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
| | | | | | | |
Collapse
|
6
|
Shin M, Copeland JM, Venton BJ. Real-Time Measurement of Stimulated Dopamine Release in Compartments of the Adult Drosophila melanogaster Mushroom Body. Anal Chem 2020; 92:14398-14407. [PMID: 33048531 DOI: 10.1021/acs.analchem.0c02305] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Drosophila melanogaster, a fruit fly, is an exquisite model organism to understand neurotransmission. Dopaminergic signaling in the Drosophila mushroom body (MB) is involved in olfactory learning and memory, with different compartments controlling aversive learning (heel) vs. appetitive learning (medial tip). Here, the goal was to develop techniques to measure endogenous dopamine in compartments of the MB for the first time. We compared three stimulation methods: acetylcholine (natural stimulus), P2X2 (chemogenetics), and CsChrimson (optogenetics). Evoked dopamine release was measured with fast-scan cyclic voltammetry in isolated adult Drosophila brains. Acetylcholine stimulated the largest dopamine release (0.40 μM) followed by P2X2 (0.14 μM) and CsChrimson (0.07 μM). With the larger acetylcholine and P2X2 stimulations, there were no regional or sex differences in dopamine release. However, with CsChrimson, dopamine release was significantly higher in the heel than the medial tip, and females had more dopamine than males. Michaelis-Menten modeling of the single-light pulse revealed no significant regional differences in Km, but the heel had a significantly lower Vmax (0.12 μM/s vs. 0.19 μM/s) and higher dopamine release (0.05 μM vs. 0.03 μM). Optogenetic experiments are challenging because CsChrimson is also sensitive to blue light used to activate green fluorescent protein, and thus, light exposure during brain dissection must be minimized. These experiments expand the toolkit for measuring endogenous dopamine release in Drosophila, introducing chemogenetic and optogenetic experiments for the first time. With a variety of stimulations, different experiments will help improve our understanding of neurochemical signaling in Drosophila.
Collapse
Affiliation(s)
- Mimi Shin
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901, United States
| | - Jeffrey M Copeland
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901, United States.,Department of Biology, Eastern Mennonite University, Harrisonburg, Virginia 22802, United States
| | - B Jill Venton
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901, United States
| |
Collapse
|
7
|
Miliano C, Marti M, Pintori N, Castelli MP, Tirri M, Arfè R, De Luca MA. Neurochemical and Behavioral Profiling in Male and Female Rats of the Psychedelic Agent 25I-NBOMe. Front Pharmacol 2019; 10:1406. [PMID: 31915427 PMCID: PMC6921684 DOI: 10.3389/fphar.2019.01406] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 11/05/2019] [Indexed: 11/13/2022] Open
Abstract
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.
Collapse
Affiliation(s)
- Cristina Miliano
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
| | - Matteo Marti
- National Institute of Neuroscience (INN), Universirty of Cagliari, Cagliari, Italy.,Department of Morphology, Experimental Medicine and Surgery, Section of Legal Medicine and LTTA Centre, University of Ferrara, Ferrara, Italy.,Collaborative Center for the Italian National Early Warning System, Department of Anti-Drug Policies, Presidency of the Council of Ministers, Rome, Italy
| | - Nicholas Pintori
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
| | - Maria Paola Castelli
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy.,National Institute of Neuroscience (INN), Universirty of Cagliari, Cagliari, Italy
| | - Micaela Tirri
- Department of Morphology, Experimental Medicine and Surgery, Section of Legal Medicine and LTTA Centre, University of Ferrara, Ferrara, Italy
| | - Raffaella Arfè
- Department of Morphology, Experimental Medicine and Surgery, Section of Legal Medicine and LTTA Centre, University of Ferrara, Ferrara, Italy.,Institute of Public Health, Section of Legal Medicine, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Maria Antonietta De Luca
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy.,National Institute of Neuroscience (INN), Universirty of Cagliari, Cagliari, Italy
| |
Collapse
|
8
|
Sylvestre MP, Chagnon M, Wellman RJ, Dugas EN, O’Loughlin J. Sex Differences in Attaining Cigarette Smoking and Nicotine Dependence Milestones Among Novice Smokers. Am J Epidemiol 2018. [PMID: 29522067 DOI: 10.1093/aje/kwy045] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
There may be sex differences in the response to nicotine, according to findings of studies in animals; however, sex differences in the natural course of cigarette smoking and nicotine dependence are documented in few studies. Prevalent (n = 240 girls; n = 184 boys) and incident (n = 231 girls; n = 184 boys) cigarette smokers from the Nicotine Dependence in Teens Study were followed up to 5 years after first puff, from age 12 to 18 years (1999-2005). We used Cox proportional hazards models to compare time to development of 3 cigarette-use (i.e., whole cigarette; 100 cigarettes lifetime; regular smoking), and 3 nicotine-dependence symptom (i.e., "really need a cigarette"; mentally addicted; physically addicted) milestones across sex. Girls were at higher risk than boys of attaining all milestones; hazard ratios (95% confidence intervals) ranged from 1.35 (1.06, 1.72) for 100 cigarettes lifetime to 1.74 (1.44, 2.10) for "really need a cigarette." Among nonregular smokers, 26% (8%; 43%) and 25% (6%; 44%) more girls than boys reported "really need a cigarette" 1 and 2 years, respectively, after first puff. Preventive interventions may need adjustment to incorporate these findings. Additional research should clarify the relative contribution of biological and social underpinnings of these sex differences.
Collapse
Affiliation(s)
- Marie-Pierre Sylvestre
- Centre de recherche du Centre Hospitalier de l’Université de Montréal, Montréal, Québec, Canada
- Department of Social and Preventive Medicine, School of Public Health, University of Montréal, Montréal, Quebec, Canada
| | - Miguel Chagnon
- Centre de recherche du Centre Hospitalier de l’Université de Montréal, Montréal, Québec, Canada
- Department of Social and Preventive Medicine, School of Public Health, University of Montréal, Montréal, Quebec, Canada
| | - Robert J Wellman
- Department of Family Medicine and Community Health, University of Massachusetts Medical School, Worcester, Massachusetts
| | - Erika N Dugas
- Centre de recherche du Centre Hospitalier de l’Université de Montréal, Montréal, Québec, Canada
| | - Jennifer O’Loughlin
- Centre de recherche du Centre Hospitalier de l’Université de Montréal, Montréal, Québec, Canada
- Department of Social and Preventive Medicine, School of Public Health, University of Montréal, Montréal, Quebec, Canada
| |
Collapse
|
9
|
Tonn Eisinger KR, Larson EB, Boulware MI, Thomas MJ, Mermelstein PG. Membrane estrogen receptor signaling impacts the reward circuitry of the female brain to influence motivated behaviors. Steroids 2018; 133:53-59. [PMID: 29195840 PMCID: PMC5864533 DOI: 10.1016/j.steroids.2017.11.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 11/20/2017] [Accepted: 11/23/2017] [Indexed: 12/12/2022]
Abstract
Within the adult female, estrogen signaling is well-described as an integral component of the physiologically significant hypothalamic-pituitary-gonadal axis. In rodents, the timing of ovulation is intrinsically entwined with the display of sexual receptivity. For decades, the importance of estradiol activating intracellular estrogen receptors within the hypothalamus and midbrain/spinal cord lordosis circuits has been appreciated. These signaling pathways primarily account for the ability of the female to reproduce. Yet, often overlooked is that the desire to reproduce is also tightly regulated by estrogen receptor signaling. This lack of emphasis can be attributed to an absence of nuclear estrogen receptors in brain regions associated with reward, such as the nucleus accumbens, which are associated with motivated behaviors. This review outlines how membrane-localized estrogen receptors affect metabotropic glutamate receptor signaling within the rodent nucleus accumbens. In addition, we discuss how, as estrogens drive increased motivation for reproduction, they also produce the untoward side effect of heightening female vulnerability to drug addiction.
Collapse
Affiliation(s)
- Katherine R Tonn Eisinger
- Department of Neuroscience and Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Erin B Larson
- Department of Neuroscience and Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Marissa I Boulware
- Department of Obstetrics and Gynecology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Mark J Thomas
- Department of Neuroscience and Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Paul G Mermelstein
- Department of Neuroscience and Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
| |
Collapse
|
10
|
Cross SJ, Linker KE, Leslie FM. Sex-dependent effects of nicotine on the developing brain. J Neurosci Res 2017; 95:422-436. [PMID: 27870426 DOI: 10.1002/jnr.23878] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 07/08/2016] [Accepted: 07/14/2016] [Indexed: 02/06/2023]
Abstract
The use of tobacco products represents a major public health concern, especially among women. Epidemiological data have consistently demonstrated that women have less success quitting tobacco use and a higher risk for developing tobacco-related diseases. The deleterious effects of nicotine are not restricted to adulthood, as nicotinic acetylcholine receptors regulate critical aspects of neural development. However, the exact mechanisms underlying the particular sensitivity of women to develop tobacco dependence have not been well elucidated. In this mini-review, we show that gonadal hormone-mediated sexual differentiation of the brain may be an important determinant of sex differences in the effects of nicotine. We highlight direct interactions between sex steroid hormones and ligand-gated ion channels critical for brain maturation, and discuss the extended and profound sexual differentiation of the brain. We emphasize that nicotine exposure during the perinatal and adolescent periods interferes with normal sexual differentiation and can induce long-lasting, sex-dependent alterations in neuronal structure, cognitive and executive function, learning and memory, and reward processing. We stress important age and sex differences in nicotine's effects and emphasize the importance of including these factors in preclinical research that models tobacco dependence. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Sarah J Cross
- Department of Anatomy and Neurobiology, School of Medicine, University of California, Irvine, California
| | - Kay E Linker
- Department of Anatomy and Neurobiology, School of Medicine, University of California, Irvine, California
| | - Frances M Leslie
- Department of Anatomy and Neurobiology, School of Medicine, University of California, Irvine, California.,Department of Pharmacology, School of Medicine, University of California, Irvine, California
| |
Collapse
|
11
|
Sex differences and the role of dopamine receptors in the reward-enhancing effects of nicotine and bupropion. Psychopharmacology (Berl) 2017; 234:187-198. [PMID: 27695921 DOI: 10.1007/s00213-016-4448-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 09/20/2016] [Indexed: 12/27/2022]
Abstract
RATIONALE Nicotine and bupropion have been demonstrated to enhance the value of other reinforcers, and this may partially account for nicotine reward and dependence. Evidence suggests that the sexes differ in their sensitivity to the primary and secondary reinforcing effects of nicotine and nicotine-associated stimuli. Whether the sexes also differ in sensitivity to the reward-enhancing effects of nicotine (and bupropion) is yet unclear. OBJECTIVES The present study evaluated potential sex differences in the enhancement effects of nicotine and bupropion using a reinforcer demand approach. Furthermore, we sought to investigate the role that D1- and D2-type dopamine receptors play in the reward-enhancing effects of nicotine and bupropion. METHODS Demand for sensory reinforcement was assessed in male and female rats responding on a progression of fixed ratio schedules. The effects of nicotine and 10 or 20 mg/kg bupropion on reinforcer demand were assessed within subjects. Subsequently, the effects of SCH-23390 and eticlopride were assessed on the enhancing effects of nicotine and bupropion on progressive ratio responding. RESULTS Nicotine and bupropion enhanced demand metrics of reinforcement value in both sexes. Females were more sensitive to the enhancement effects of bupropion assessed by reinforcer demand and progressive ratio performance. D2-like dopamine receptor antagonism by eticlopride attenuated the enhancement effects of bupropion, but not of nicotine. CONCLUSIONS Nicotine and bupropion both enhance reinforcement value in both sexes, though females may be more sensitive to the reward-enhancing effects of bupropion. D2- and possibly D1-type receptors appear to be involved in the reward-enhancing effects of bupropion, but not necessarily nicotine.
Collapse
|
12
|
Kuhn C. Emergence of sex differences in the development of substance use and abuse during adolescence. Pharmacol Ther 2015; 153:55-78. [PMID: 26049025 DOI: 10.1016/j.pharmthera.2015.06.003] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 04/29/2015] [Indexed: 12/24/2022]
Abstract
Substance use and abuse begin during adolescence. Male and female adolescent humans initiate use at comparable rates, but males increase use faster. In adulthood, more men than women use and abuse addictive drugs. However, some women progress more rapidly from initiation of use to entry into treatment. In animal models, adolescent males and females consume addictive drugs similarly. However, reproductively mature females acquire self-administration faster, and in some models, escalate use more. Sex/gender differences exist in neurobiologic factors mediating both reinforcement (dopamine, opioids) and aversiveness (CRF, dynorphin), as well as intrinsic factors (personality, psychiatric co-morbidities) and extrinsic factors (history of abuse, environment especially peers and family) which influence the progression from initial use to abuse. Many of these important differences emerge during adolescence, and are moderated by sexual differentiation of the brain. Estradiol effects which enhance both dopaminergic and CRF-mediated processes contribute to the female vulnerability to substance use and abuse. Testosterone enhances impulsivity and sensation seeking in both males and females. Several protective factors in females also influence initiation and progression of substance use including hormonal changes of pregnancy as well as greater capacity for self-regulation and lower peak levels of impulsivity/sensation seeking. Same sex peers represent a risk factor more for males than females during adolescence, while romantic partners increase risk for women during this developmental epoch. In summary, biologic factors, psychiatric co-morbidities as well as personality and environment present sex/gender-specific risks as adolescents begin to initiate substance use.
Collapse
Affiliation(s)
- Cynthia Kuhn
- Department of Pharmacology and Cancer Biology, Box 3813, Duke University Medical Center, Durham, NC 27710, United States.
| |
Collapse
|
13
|
Zhou L, Pruitt C, Shin CB, Garcia AD, Zavala AR, See RE. Fos expression induced by cocaine-conditioned cues in male and female rats. Brain Struct Funct 2014; 219:1831-40. [PMID: 23832598 PMCID: PMC3877704 DOI: 10.1007/s00429-013-0605-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 06/24/2013] [Indexed: 02/04/2023]
Abstract
Previous studies have shown that female rats exhibit different patterns of drug seeking during multiple phases of cocaine addiction when compared with males. However, the underlying mechanisms for these sex differences remain largely unknown. Here, we used a cocaine self-administration/reinstatement model to examine neuronal activation, as determined by Fos expression, following cue-induced reinstatement of cocaine seeking in male and female rats. Fos expression revealed both similarities between sexes in some brain regions, as well as selective sexually dimorphic patterns. As compared to no cue control subjects, conditioned cues induced higher Fos expression in the Cg1 region of the anterior cingulate cortex, but lower expression in the nucleus accumbens in both males and females. Females exhibited higher Fos expression than males in multiple brain regions, including the agranular insular cortex, dorsal medial caudate-putamen, nucleus accumbens shell, ventral tegmental area, dorsal subiculum, and ventral CA1 and CA3 regions of the hippocampus. Notably, only Fos expression in the prelimbic cortex, nucleus accumbens shell, basolateral amygdala, and ventral subiculum correlated positively with lever responding in response to conditioned cues across males and females. These findings indicate that while sexually dimorphic Fos activation does occur, the relationship between cue-induced cocaine seeking and neuronal activation may be similar for males and females in key brain regions of the relapse circuit.
Collapse
Affiliation(s)
- Luyi Zhou
- Department of Neurosciences, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC, 29425, USA,
| | | | | | | | | | | |
Collapse
|
14
|
“Sexy stimulants”: The interaction between psychomotor stimulants and sexual behavior in the female brain. Pharmacol Biochem Behav 2014; 121:53-61. [DOI: 10.1016/j.pbb.2013.11.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 11/06/2013] [Indexed: 11/19/2022]
|
15
|
High-frequency stimulation of the subthalamic nucleus counteracts cortical expression of major histocompatibility complex genes in a rat model of Parkinson's disease. PLoS One 2014; 9:e91663. [PMID: 24621597 PMCID: PMC3951430 DOI: 10.1371/journal.pone.0091663] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2012] [Accepted: 02/14/2014] [Indexed: 11/19/2022] Open
Abstract
High-frequency stimulation of the subthalamic nucleus (STN-HFS) is widely used as therapeutic intervention in patients suffering from advanced Parkinson’s disease. STN-HFS exerts a powerful modulatory effect on cortical motor control by orthodromic modulation of basal ganglia outflow and via antidromic activation of corticofugal fibers. However, STN-HFS-induced changes of the sensorimotor cortex are hitherto unexplored. To address this question at a genomic level, we performed mRNA expression analyses using Affymetrix microarray gene chips and real-time RT-PCR in sensorimotor cortex of parkinsonian and control rats following STN-HFS. Experimental parkinsonism was induced in Brown Norway rats by bilateral nigral injections of 6-hydroxydopamine and was assessed histologically, behaviorally, and electrophysiologically. We applied prolonged (23h) unilateral STN-HFS in awake and freely moving animals, with the non-stimulated hemisphere serving as an internal control for gene expression analyses. Gene enrichment analysis revealed strongest regulation in major histocompatibility complex (MHC) related genes. STN-HFS led to a cortical downregulation of several MHC class II (RT1-Da, Db1, Ba, and Cd74) and MHC class I (RT1CE) encoding genes. The same set of genes showed increased expression levels in a comparison addressing the effect of 6-hydroxydopamine lesioning. Hence, our data suggest the possible association of altered microglial activity and synaptic transmission by STN-HFS within the sensorimotor cortex of 6-hydroxydopamine treated rats.
Collapse
|
16
|
Cummings JA, Jagannathan L, Jackson LR, Becker JB. Sex differences in the effects of estradiol in the nucleus accumbens and striatum on the response to cocaine: neurochemistry and behavior. Drug Alcohol Depend 2014; 135:22-8. [PMID: 24332790 PMCID: PMC3947194 DOI: 10.1016/j.drugalcdep.2013.09.009] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 08/27/2013] [Accepted: 09/08/2013] [Indexed: 11/27/2022]
Abstract
BACKGROUND Females exhibit more rapid escalation of cocaine use and enhanced cocaine-taking behavior as compared to males. While ovarian hormones likely play a role in this increased vulnerability, research has yet to examine the role of estradiol in affecting the behavioral and neurological response to cocaine in a brain region- and sex-specific way. METHODS First, we examined stereotypy and locomotor sensitization after repeated cocaine administration (10 mg/kg i.p.) in intact (SHAM) and castrated (CAST) males, and ovariectomized (OVX) females treated with 5 μg estradiol benzoate (EB) or vehicle (OIL). Next, we used in vivo microdialysis to examine the effects of acute EB treatment on cocaine-induced DA in the regions mediating the display of these behaviors (i.e., the dorsolateral striatum, DLS; and the nucleus accumbens, NAc; respectively). RESULTS We find that EB enhances sensitization of cocaine-induced stereotypy in OVX females after 12 days of cocaine treatment, and after a 10-day withdrawal. Similarly, the OVX/EB females show enhanced locomotor sensitization compared to the other three groups on the same days. Using in vivo microdialysis to assess the neurochemical response, we find that EB rapidly enhances cocaine-induced DA in DLS dialysate of OVX females but not CAST males, and has no effect in NAc of either sex. CONCLUSIONS With these experiments, we show that there are sex differences in the effects of estradiol to preferentially enhance the response to cocaine in the DLS over the NAc in females, which may contribute to the preferential sensitization of stereotypy in females.
Collapse
Affiliation(s)
- Jennifer A Cummings
- Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, United States
| | - Lakshmikripa Jagannathan
- Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, United States
| | - Lisa R Jackson
- Department of Psychology, Schoolcraft College, Livonia, MI 48152, United States
| | - Jill B Becker
- Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, United States; Department of Psychology, University of Michigan, Ann Arbor, MI 48109, United States; Department of Psychiatry, University of Michigan, Ann Arbor, MI 48109, United States.
| |
Collapse
|
17
|
Goebrecht GKE, Kowtoniuk RA, Kelly BG, Kittelberger JM. Sexually-dimorphic expression of tyrosine hydroxylase immunoreactivity in the brain of a vocal teleost fish (Porichthys notatus). J Chem Neuroanat 2014; 56:13-34. [PMID: 24418093 DOI: 10.1016/j.jchemneu.2014.01.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 01/04/2014] [Accepted: 01/04/2014] [Indexed: 12/23/2022]
Abstract
Vocal communication has emerged as a powerful model for the study of neural mechanisms of social behavior. Modulatory neurochemicals postulated to play a central role in social behavior, related to motivation, arousal, incentive and reward, include the catecholamines, particularly dopamine and noradrenaline. Many questions remain regarding the functional mechanisms by which these modulators interact with sensory and motor systems. Here, we begin to address these questions in a model system for vocal and social behavior, the plainfin midshipman fish (Porichthys notatus). We mapped the distribution of immunoreactivity for the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH) in the midshipman brain. The general pattern of TH(+) cell groups in midshipman appears to be highly conserved with other teleost fish, with a few exceptions, including the apparent absence of pretectal catecholamine cells. Many components of the midshipman vocal and auditory systems were innervated by TH(+) fibers and terminals, including portions of the subpallial area ventralis, the preoptic complex, and the anterior hypothalamus, the midbrain periaqueductal gray and torus semicircularis, several hindbrain auditory nuclei, and parts of the hindbrain vocal pattern generator. These areas thus represent potential sites for catecholamine modulation of vocal and/or auditory behavior. To begin to test functionally whether catecholamines modulate vocal social behaviors, we hypothesized that male and female midshipman, which are sexually dimorphic in both their vocal-motor repertoires and in their responses to hearing conspecific vocalizations, should exhibit sexually dimorphic expression of TH immunoreactivity in their vocal and/or auditory systems. We used quantitative immunohistochemical techniques to test this hypothesis across a number of brain areas. We found significantly higher levels of TH expression in male midshipman relative to females in the TH cell population in the paraventricular organ of the diencephalon and in the TH-innervated torus semicircularis, the main teleost midbrain auditory structure. The torus semicircularis has been implicated in sexually dimorphic behavioral responses to conspecific vocalizations. Our data thus support the general idea that catecholamines modulate vocal and auditory processing in midshipman, and the specific hypothesis that they shape sexually dimorphic auditory responses in the auditory midbrain.
Collapse
Affiliation(s)
- Geraldine K E Goebrecht
- Department of Biology, Gettysburg College, 300 North Washington Street, Gettysburg, PA 17325, USA.
| | - Robert A Kowtoniuk
- Department of Biology, Gettysburg College, 300 North Washington Street, Gettysburg, PA 17325, USA.
| | - Brenda G Kelly
- Department of Biology, Gettysburg College, 300 North Washington Street, Gettysburg, PA 17325, USA.
| | - J Matthew Kittelberger
- Department of Biology, Gettysburg College, 300 North Washington Street, Gettysburg, PA 17325, USA.
| |
Collapse
|
18
|
Grieb B, von Nicolai C, Engler G, Sharott A, Papageorgiou I, Hamel W, Engel AK, Moll CK. Decomposition of abnormal free locomotor behavior in a rat model of Parkinson's disease. Front Syst Neurosci 2013; 7:95. [PMID: 24348346 PMCID: PMC3842038 DOI: 10.3389/fnsys.2013.00095] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Accepted: 11/08/2013] [Indexed: 11/13/2022] Open
Abstract
Poverty of spontaneous movement, slowed execution and reduced amplitudes of movement (akinesia, brady- and hypokinesia) are cardinal motor manifestations of Parkinson's disease that can be modeled in experimental animals by brain lesions affecting midbrain dopaminergic neurons. Most behavioral investigations in experimental parkinsonism have employed short-term observation windows to assess motor impairments. We postulated that an analysis of longer-term free exploratory behavior could provide further insights into the complex fine structure of altered locomotor activity in parkinsonian animals. To this end, we video-monitored 23 h of free locomotor behavior and extracted several behavioral measures before and after the expression of a severe parkinsonian phenotype following bilateral 6-hydroxydopamine (6-OHDA) lesions of the rat dopaminergic substantia nigra. Unbiased stereological cell counting verified the degree of midbrain tyrosine hydroxylase positive cell loss in the substantia nigra and ventral tegmental area. In line with previous reports, overall covered distance and maximal motion speed of lesioned animals were found to be significantly reduced compared to controls. Before lesion surgery, exploratory rat behavior exhibited a bimodal distribution of maximal speed values obtained for single movement episodes, corresponding to a "first" and "second gear" of motion. 6-OHDA injections significantly reduced the incidence of second gear motion episodes and also resulted in an abnormal prolongation of these fast motion events. Likewise, the spatial spread of such episodes was increased in 6-OHDA rats. The increase in curvature of motion tracks was increased in both lesioned and control animals. We conclude that the discrimination of distinct modes of motion by statistical decomposition of longer-term spontaneous locomotion provides useful insights into the fine structure of fluctuating motor functions in a rat analog of Parkinson's disease.
Collapse
Affiliation(s)
- Benjamin Grieb
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, University of Hamburg Hamburg, Germany ; Department of General Psychiatry, Center for Psychosocial Medicine, University of Heidelberg Heidelberg, Germany
| | - Constantin von Nicolai
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, University of Hamburg Hamburg, Germany ; Centre for Integrative Neuroscience, University of Tübingen Tübingen, Germany
| | - Gerhard Engler
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, University of Hamburg Hamburg, Germany
| | - Andrew Sharott
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, University of Hamburg Hamburg, Germany ; Medical Research Council, Anatomical Neuropharacology Unit, Department of Pharmacology, University of Oxford Oxford, UK
| | - Ismini Papageorgiou
- Division of General Neurophysiology, Institute of Physiology and Pathophysiology, University of Heidelberg Heidelberg, Germany
| | - Wolfgang Hamel
- Department of Neurosurgery, University Medical Center Hamburg-Eppendorf, University of Hamburg Hamburg, Germany
| | - Andreas K Engel
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, University of Hamburg Hamburg, Germany
| | - Christian K Moll
- Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, University of Hamburg Hamburg, Germany
| |
Collapse
|
19
|
Aumann TD, Tomas D, Horne MK. Environmental and behavioral modulation of the number of substantia nigra dopamine neurons in adult mice. Brain Behav 2013; 3:617-25. [PMID: 24363965 PMCID: PMC3868167 DOI: 10.1002/brb3.163] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Revised: 06/25/2013] [Accepted: 07/26/2013] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND Recent evidence indicates that hypothalamic neurons acquire or lose the capacity to synthesize and release dopamine (DA) in response to environmental stimuli, and this has functional and behavioral consequences for adult rats. We have evidence that neuronal activity, including that driven by afferent input, regulates acquisition and loss of the DA phenotype by substantia nigra pars compacta (SNc) neurons in adult mice. Hypotheses The aims of the present study were to determine whether the environment or behavior regulates the number of SNc DA neurons in adult mice, and whether this is mediated by afferent input. METHODS ADULT MICE WERE SUBJECT TO TWO DIFFERENT ENVIRONMENTS/BEHAVIORS: "mating" for 1 week or "environment enrichment" (EE) for 2 weeks; then the numbers of tyrosine hydroxylase (TH, the rate limiting enzyme in DA synthesis) immunopositive (TH+) and immunonegative (TH-) SNc neurons were counted. RESULTS More TH+ neurons were present in mated males whereas less TH+ neurons were present in mated females. Also, more TH+ neurons were present in EE males, and this increase was completely abolished by concurrent local infusion of GABAA receptor antagonists. CONCLUSIONS The number of DA neurons in the adult SNc is not fixed, but readily increases and decreases in response to environmental stimuli and/or behaviors. These changes are mediated by afferent input relaying information about the environment or behavior to SNc neurons.
Collapse
Affiliation(s)
- Tim D Aumann
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne Parkville, Victoria, Australia, 3010
| | - Doris Tomas
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne Parkville, Victoria, Australia, 3010
| | - Malcolm K Horne
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne Parkville, Victoria, Australia, 3010
| |
Collapse
|
20
|
Van Swearingen AED, Sanchez CL, Frisbee SM, Williams A, Walker QD, Korach KS, Kuhn CM. Estradiol replacement enhances cocaine-stimulated locomotion in female C57BL/6 mice through estrogen receptor alpha. Neuropharmacology 2013; 72:236-49. [PMID: 23608737 DOI: 10.1016/j.neuropharm.2013.04.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Revised: 04/05/2013] [Accepted: 04/10/2013] [Indexed: 12/22/2022]
Abstract
Psychostimulant effects are enhanced by ovarian hormones in women and female rodents. Estradiol increases behavioral responses to psychostimulants in women and female rats, although the underlying mechanism is unknown. This study utilized mice to investigate the time frame and receptor mediation of estradiol's enhancement of cocaine-induced behavior as mice enable parallel use of genetic, surgical and pharmacological methods. The spontaneous behavior of Sham and Ovariectomized (Ovx) female wildtype (WT) mice was determined during habituation to a novel environment and after cocaine administration. Ovx mice were replaced with vehicle (sesame oil) or 17β-estradiol (E2) for 2 days or 30 min prior to a cocaine challenge to investigate the time course of E2's effects. To examine receptor mediation of estradiol effects, Ovx mice replaced for 2 days with either the ERα-selective agonist PPT or the ERβ-selective agonist DPN were compared to Sham mice, and mice lacking either ERα (αERKO) or ERβ (βERKO) were compared to WT littermates. Ovx mice exhibited fewer ambulations during habituation than Sham females. Cocaine-induced increases in behavioral ratings were greater in Sham than in Ovx mice. Two days but not 30 min of E2 replacement in Ovx mice increased cocaine responses to Sham levels. PPT replacement also increased the cocaine response relative to vehicle- or DPN- treated Ovx mice. αERKO mice displayed modestly attenuated behavioral responses to novelty and cocaine compared to αWT littermates, but no behavioral differences were found between βERKO and βWT mice. These results suggest that E2 enhances cocaine-stimulated locomotion in mice predominantly through ERα.
Collapse
Affiliation(s)
- Amanda E D Van Swearingen
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
| | | | | | | | | | | | | |
Collapse
|
21
|
Sex differences in novelty- and psychostimulant-induced behaviors of C57BL/6 mice. Psychopharmacology (Berl) 2013; 225:707-18. [PMID: 22975726 PMCID: PMC3547129 DOI: 10.1007/s00213-012-2860-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 08/20/2012] [Indexed: 01/16/2023]
Abstract
RATIONALE Women are more sensitive than men to psychostimulants and progress from initial use to drug addiction more quickly. The mouse has been an under-utilized model to study sex differences in psychostimulant action. Mice could serve as an ideal genetically tractable model for mechanistic studies into sex and hormone effects on psychostimulant behavior. OBJECTIVES The objective of this study was to characterize psychostimulant effects in male and female mice with a combination of automated data collection and behavioral observation. METHODS Male and female C57BL/6 mice (Charles River) were given a single dose or sequential ascending binge doses of D-amphetamine (AMPH) or cocaine (COC). Behavior was assessed in open field chambers using both automated photobeam interruptions and behavioral observations. Brain psychostimulant concentrations were determined at the time of maximum behavioral stimulation. RESULTS Psychostimulants induced behavioral activation in mice including both increased locomotion as detected with an automated system and a sequence of behaviors progressing from stereotyped sniffing at low doses to patterned locomotion and rearing at high doses. Females exhibited more patterned locomotion and a shift towards higher behavior scores after either psychostimulant despite having lower AMPH and equivalent COC brain levels as males. CONCLUSIONS Female C57BL/6 mice exhibit enhanced psychostimulant-induced behavior compared to males, similar to reports in rats. The combination of automated behavioral measures and behavioral observation was essential for verifying the existence of these differences. These results indicate the importance of testing both sexes when characterizing genetically manipulated mice to control for potential sex-specific effects.
Collapse
|