Estradiol enhances behavioral sensitization to cocaine and amphetamine-stimulated striatal [3H]dopamine release

Ovariectomy and estradiol treatment affect the dopamine transporter and its gene expression in the rat brain

The impact of gonadal hormone withdrawal and estrogen therapy was investigated on the rat dopamine transporter (DAT). Short-term ovariectomized (ST-OVX, 2 weeks) and long-term ovariectomized (LT-OVX, 3 months) rats were treated or not with 17beta-estradiol (E2) for 2 weeks. DAT mRNA expression was measured by in situ hybridization in the substantia nigra pars compacta (SNc) for the nigrostriatal pathway and the ventral tegmental area (VTA) for the mesolimbic pathway whereas DAT levels were assessed by [3H]GBR-12935 autoradiography, respectively, in the striatum and the nucleus accumbens. Ovariectomy produced a time-dependent decrease of the DAT density in the striatum and the nucleus accumbens and the E2 treatment did not significantly restore these DAT levels. Neither ST-OVX nor E2 treatment of the ST-OVX animals altered the DAT mRNA expression in the SNc and the VTA. However, LT-OVX animals showed increased DAT mRNA levels in these regions. E2 treatment of LT-OVX animals partially restored DAT mRNA levels in the SNc and left these levels unchanged in the VTA. These opposite variations induced by OVX on the DAT density and their mRNA levels suggest the involvement of non-genomic mechanisms, such as post-transcriptional events and/or membrane effects. Altered neurotransmission following gonadal hormone withdrawal may contribute to CNS disorders occurring at menopause in predisposed women. Ovariectomized rats constitute a useful model to study the changes in neurotransmitters balance occurring after menopause.

The effect of ginseng extract on locomotor sensitization and conditioned place preference induced by methamphetamine and cocaine in mice

Repeated i.p. injections of 2 mg/kg methamphetamine (MA) or 20 mg/kg cocaine at 48-h intervals induced reverse tolerance to their ambulation-enhancing effects (behavioral sensitization). Furthermore, the reappearance of the sensitized state was observed at the time of readministration of MA or cocaine even after a 30-day discontinuation of drug administration. A concomitant injection of ginseng extract (GE), 200 mg/kg, i.p., suppressed the development of reverse tolerance and the reappearance of sensitization to MA and cocaine. Conditioned place preference to MA (1, 2, and 4 mg/kg, i.p.) and cocaine (1, 4, 10, and 20 mg/kg, i.p.), was completely blocked by GE, 200 mg/kg, i.p. combined treatment with MA of cocaine. Meanwhile, spontaneous motor activity and place preference were not affected by GE alone. These results provide evidence that GE may be useful clinically for the prevention of adverse actions of MA and cocaine.

Clinically relevant EEG studies and psychophysiological findings: possible neural mechanisms for multiple chemical sensitivity

This paper addresses the evidence for the face, construct, and criterion-related validity of the olfactory-limbic/neural sensitization model for multiple chemical sensitivity (MCS). MCS is a poorly-understood, controversial condition in which low levels of environmental chemicals are reported to trigger disabling levels of illness in certain individuals. Neural sensitization processes could generate an endogenous amplification of responsivity to exogenous substances, thereby providing a plausible explanation for the apparent lack of a classical toxicological dose-response relationship in MCS. Convergent data from both survey and psychophysiological studies of MCS patients and of persons from the community without MCS, but who report elevated frequency of illness from chemical odors (cacosmics), support the involvement of the limbic system and the sensitizability of cacosmics, as predicted by the model. Recent studies show that cacosmics do sensitize their heart rate, blood pressure, and plasma beta-endorphin responses to repeated exposures to a novel laboratory procedure involving dietary manipulations over time. Cacosmia may represent a pathological form of neural plasticity. Taken together, the model and the available evidence suggest the need for more intensive investigation of MCS from the standpoint of possible neurobiological mechanisms affecting cognitive, emotional, and somatic functions.

Neuropsychiatric and somatic characteristics of young adults with and without self-reported chemical odor intolerance and chemical sensitivity

The psychological, neuropsychiatric, and somatic characteristics of young adults who have different degrees of cacosmia (i.e., feeling "ill" from the odor of xenobiotic chemicals) and who have self-described "chemical sensitivity" were examined. A total of 800 college students completed the following: a self-rating scale for frequency of odor intolerance for 10 common substances, Simon Environmental Illness Symptom Survey, the SCL-90-R, Barsky Amplification Scale, Pearlin-Schooler Mastery Scale, Cheek-Buss and Kagan Shyness scales, Marlowe-Crowne Social Desirability Scale, and a health-symptom and physician-diagnosed checklist. Two pairs of groups were compared: (1) subjects in the top 16% (i.e., cacosmics) and bottom 15% (noncacosmics) of the sample with respect to odor intolerance scale scores; and (2) subjects from the entire sample who did (28%) or did not (72%) consider themselves to be "especially sensitive to certain chemicals.¿ Cacosmics and the chemically sensitive subjects scored significantly higher on measures of psychological distress and amplification of somatic symptoms, but there was little evidence of lifestyle change, as assessed by the Simon Survey. Compared with their respective comparison groups, cacosmic and chemically sensitive groups had significantly higher incidences of illnesses associated with chemicals, alcohol intake, opiate drug use, and caffeine use, even after controlling for the psychological measures and histories of atopic allergy. Subjects with and without neuropsychiatric symptoms were differentiated with respect to chemical odor intolerance, but subjects with and without atopic allergies and possible autoimmune diseases were differentiated with respect to chemical sensitivity. Females were more cacosmic than males. Cacosmia is defined by a population subset, with or without occupational xenobiotic exposures or disability, that has distress and symptom amplification and neuropsychiatric and somatic symptoms, none of which are explained fully by psychological measures. Prospective clinical studies are possible with such individuals. The data are also consistent with a time-dependent sensitization model for illness from low-level chemical exposures.

Smoked cocaine self-administration in females

Although approximately 32% of all smoked cocaine ("crack") users are women, most studies investigating cocaine use have recruited only male subjects. Therefore, this study examined the smoked cocaine self-administration patterns of female crack abusers. A work requirement, where up to five tokens were earned by subjects, was followed by the administration of a sample delivery of one of three dose sizes [5.0 mg (placebo), 0.2 mg/kg, 0.4 mg/kg] of cocaine. The three dose sizes of cocaine were administered in counterbalanced order across subjects, with each subject receiving one dose size within a session and all dose sizes across the three experimental sessions. A self-administration phase followed the sample delivery, during which a token could be exchanged every 30 min for monetary reimbursement or a delivery of cocaine in the same dose size as the sample delivery. The results show that females' patterns of behavioral and subjective responding to smoked cocaine exhibit clear dose-related effects, thus affirming this self-administration model as safe and appropriate for use with women.

Effects of acute and chronic cocaine administration on EEG and behaviour in intact and castrated male and intact and ovariectomized female rats

Intact and gonadectomized male and female WAG/ Rij rats were used to study the effects of gender and gonadal hormones on the development of sensitization and tolerance to cocaine-induced changes in EEG and behaviour. The four groups of WAG/Rij rats differed in the number of spontaneously occurring spike-wave discharges: ovariectomy decreased and castration increased the number of spike-wave discharges. This confirms that testosterone has antiabsence effects and that female gonadal hormones may promote the occurrence of spike-wave discharges. Cocaine [10 and 20 mg/kg, intraperitoneally (IP)] was administered before and after chronic cocaine administration (9 days, one daily injection with 10 mg/kg) and EEG and behaviour were monitored. Cocaine strongly suppressed the occurrence of spike-wave discharges before and after chronic administration in all four groups, although the decrease was less in the intact males. Sensitization or tolerance induced by cocaine on EEG could not be established. Acute cocaine administration eliminated explorative, automatic, and passive behaviour, whereas various stereotypical activities such as uncoordinated head and body movements and head swaying emerged. Differences between groups were observed as intact males were less likely than subjects in the three other groups to engage in intense stereotyped behaviour. These data suggest that testosterone inhibits EEG and behavioural effects of acute cocaine administration. All four groups displayed less head swaying and more uncoordinated head and body movements after chronic cocaine administration, suggesting that behavioural sensitization had occurred. Differences between the four groups had faded away. Although pharmacokinetic differences in levels of cocaine and benzoylecgonine between the four groups were found, they could not easily be related to the behavioural differences between groups.

Brain dopamine transporter: gender differences and effect of chronic haloperidol

Gender differences and the effect of chronic haloperidol on the rat brain dopamine transporter is reported. The density of striatal dopamine transporter sites labelled with [3H]GBR 12935, and of substantia nigra dopamine transporter mRNA measured by in situ hybridization were higher in female compared to male rats whereas striatal D2 specific binding labelled with [3H]spiperone was not significantly higher. Daily haloperidol treatment (1 mg/kg, i.p.) for 21 days increased striatal [3H]spiperone specific binding but left unchanged striatal [3H]GBR 12935 binding density and affinity as well as substantia nigra dopamine transporter mRNA levels. A reduce clearance rate of dopamine in the striatum after acute and chronic haloperidol was previously reported; the present results indicate that this may occur without changes in the sites of dopamine transport or in gene expression of this transporter.

Sensitization to early life stress and response to chemical odors in older adults

This study examined the hypothesis that older persons who currently report illness from environmental chemical odors (cacosmia) may have experienced higher levels of stress early in life than did noncacosmic controls. The hypothesis derives from a time-dependent sensitization (TDS) model for cacosmia (Bell et al 1992) that predicts a relative interchangeability of stress and chemicals in inducing and eliciting sensitized responses in vulnerable individuals. Subjects were selected from those in the top 24% (cacosmic) and bottom 27% (noncacosmic) of a sample of 192 older adults (mean age 73.8 years) for self-reported frequency of illness form the odors of pesticide, car exhaust, paint, perfume, and new carpet. As in previous investigations, cacosmics were younger, more depressed, and more shy; cacosmics also included a higher proportion of women (83% versus 61%). As predicted, cacosmics rated themselves higher in stress for the first four decades of their lives, but not the recent past or present, even after controlling for depression, anxiety, hostility, shyness, age, and gender. Cacosmics reported increased prevalence of physician-diagnosed nasal allergies, breast cysts, hypothyroidism, sinusitis, food sensitivities, irritable bowel, and migraine headache. Only 4% of the overall sample (including 9% of the cacosmics) acknowledged the controversial physician diagnosis of "chemical sensitivity." The replicated observation of greater shyness in cacosmics is consistent with the ability of hyperreactivity to novelty to predict enhanced susceptibility to TDS from low levels of pharmacological agents in animals. The findings support a TDS model for cacosmia and suggest that cacosmia as a symptom identifies a large subset of the nonindustrial population with significant psychophysiological health problems that merit further objective examination.

The effects of acute and chronic cocaine administration on paced responding in intact and gonadectomized male and female Wistar rats

Intact and gonadectomized male and female Wistar rats pressed a lever on a multiple (tandem Random-Interval 30-s, Differential Reinforcement of High Rate 0.5-s) (tandem Random-Interval 30-s, Differential Reinforcement of Low-Rate 5.0-s) schedule of reinforcement. The pacing requirements maintained high and low response rates under equal reinforcement frequencies. Low doses of cocaine (1 and 3 mg/kg) either did not affect or slightly increased high and low response rates of intact and gonadectomized female rats, while they did not affect or decrease high and low response rates of intact and castrated male rats. Higher doses of cocaine (up to 30 mg/kg) dose-dependently decreased both high and low response rates for all subjects. Intact male rats were less sensitive to the rate-decreasing effects of these doses of cocaine than castrated male rats or intact and ovariectomized female rats. Chronic cocaine administration consistently resulted in behavioral sensitization only in intact male subjects. The results of this experiment provide further support for the notion that the behavioral effects of psychomotor stimulant drugs are not necessarily rate dependent but may depend upon the extent to which schedule contingencies allow for behavioral variability without negatively affecting behavioral outcomes.

Prenatal cocaine eliminates the sex-dependent differences in activation observed in adult rats after cocaine challenge

In the adult rat, acute administration of cocaine results in enhanced expression of certain behaviors. This activation is often referred to as "stereotypy" because of its repetitive nature. Repeated exposure to the same dose of cocaine does not result in tolerance or a dimunition of these behavioral responses. Rather, an increased responsiveness to cocaine, termed "sensitization," is observed. Female rats, in comparison to male rats, display greater activation to a given dose of cocaine and greater sensitization with repeated exposure. As prenatal cocaine exposure can involve repeated exposure to the drug, we examined the behavioral activation induced by an acute dose of cocaine. Young adult rats of both sexes received a challenge dose of cocaine to determine the long-term effects of repeated in utero exposure to cocaine (30 mg/kg daily, SC) given between gestational days 8-20. As expected, female offspring of dams exposed to saline in utero displayed greater activation to a 20 mg/kg SC dosage of cocaine than their male counterparts. However, these sex differences were completely eliminated by prenatal exposure to cocaine. That is, female rats receiving cocaine during the prenatal period showed no more activation to an acute dose of cocaine as young adults than either control males or those males receiving cocaine in utero. Males exposed in utero to cocaine showed activation to cocaine challenge equivalent to that displayed by males exposed to saline in utero. Prenatal exposure to cocaine may alter sexual differentiation of the brain.

Modulation of brain dopamine transmission by sex steroids

Sex steroid hormones influence the dopaminergic systems of the hypothalamus as well as the extrahypothalamic regions of the brain in controlling movement and behavior in both humans and animals. This review focuses on the effects of sex steroids on dopaminergic activity in extrahypothalamic brain areas. Among sex steroids, estrogens have been most extensively investigated, and many studies report that estrogens affect behaviors mediated by the basal ganglia, such as in humans suffering from extrapyramidal disorders. Epidemiological and clinical evidence also suggests an influence of estrogens on the vulnerability threshold for schizophrenia and sex differences in the clinical expression of this disease. Clinical observations point to a role of androgenic hormones in Gilles de la Tourette's syndrome. In normal humans, sex steroids were also shown to influence motor and cognitive performance. Biochemical and behavioral studies in animals have also shown the effect of sex steroids on dopaminergic activity in the basal ganglia; however, both activating and inhibiting effects have been reported. This may partly be explained by effects of the dose, duration of treatment, interval between steroid administration and testing the behavior measured, and the part of the basal ganglia from which the behavior is elicited. In view of the numerous variables that influence net dopaminergic response to steroids, focus will be on the literature using similar experimental conditions to assess the effect of in vivo chronic steroid treatment, acute short-term steroid treatment and the estrous cycle as well as in vitro effects of steroids on dopamine receptors. These experimental paradigms point to two general mechanisms of action of steroids: a rapid short-term non-genomic membrane effect and a slower long-term possibly genomic effect of steroids on dopamine systems. Combining dopaminergic drugs with sex steroids could improve efficacy or reduce side effects associated with these drugs. Examples of such combined treatments in rats and monkeys are presented for delta 9-tetrahydrocannabinol, cocaine, neuroleptics, apomorphine and L-DOPA. A better understanding of steroid-dopamine interactions and the possible isolation of conditions to have only pro or anti dopaminergic activity could then be used to develop combined therapies or to optimize drug treatments that would take into account the patient's sex and endocrine status.

Possible time-dependent sensitization to xenobiotics: self-reported illness from chemical odors, foods, and opiate drugs in an older adult population

The present paper summarizes key features of time-dependent sensitization (TDS) in neuropharmacology (progressive amplification of behavioral, neuronal, endocrine, and/or immune responses to repeated intermittent exposures to an environmental agent or cross-sensitizing agents) as a possible model for cacosmia (subjective sense of feeling ill from low levels of environmental chemical odors) in nonindustrial and industrial populations; and extends previous cacosmia research in nonpatient populations to an elderly sample. This study examined the symptom and psychological profiles of 263 older adults (aged 60-90 y, 71% women, 29% men); 57% reported that at least one chemical and 17% reported that at least four of five chemicals (pesticide, automobile exhaust, paint, new carpet, perfume) made them feel ill. Cacosmia ratings correlated weakly and negatively with age (r = -0.19, p = .001) over the whole sample. Cacosmia correlated significantly with self-reported illness from foods that may mobilize or generate opioid peptides (wheat, dairy, eggs) (r = 0.32, p < .0001) and with illness from opiate drugs (r = 0.23, p < .0001). When the sample was divided into four cells on the basis of above-versus below-median total chemical-induced illness score (CI) and total food-induced illness score (FI), the high CI and high FI, high CI only, and high FI only groups had more frequent indigestion, and the high CI group had more frequent difficulty concentrating than the groups below median for illness from both chemicals and foods (NOILL), even after covarying for age and anxiety. The most cacosmic subjects noted higher prevalence of physician-diagnosed allergies and irritable bowel than did noncacosmic subjects. In contrast with previous young adult cohort studies, the older illness groups did not differ with regard to sex distribution, depression, shyness, or repressive defensiveness. When considered with prior surveys of young adults, the present findings are consistent with the presence of previously established, time-dependent sensitization to multiple xenobiotic agents in susceptible individuals for whom psychological variables do not explain the symptom of cacosmia. If cacosmia is a symptom of TDS, then the neuropharmacology literature suggests the possibility of excitatory amino acid, hypothalamic-pituitary-adrenal axis, dopaminergic, and/or opioid involvement. Prospective studies with objective measures testing the possible induction of TDS to specific chemicals are indicated.

Polysymptomatic syndromes and autonomic reactivity to nonfood stressors in individuals with self-reported adverse food reactions

This study compared symptom reports and cardiovascular reactivity of a group of 24 individuals recruited from the community who reported a cognitive or emotional symptom caused by at least one food (food-sensitivity reporters, FSR) vs those of 15 controls (C) without a history of food, chemical, drug, or inhalant sensitivities. The main findings were: 1) FSR indicated sensitivities not only to foods, but also to environmental chemicals, drugs, and natural inhalants, as well as significantly more symptoms than C in multiple systems; 2) more FSR than C noted recent state depression and anxiety, as well as higher trait anxiety on the Bendig form of the Taylor Manifest Anxiety Scale; 3) however, on multiple regression analysis, not only depression, but also the number of sensitivities (foods, chemicals, drugs, inhalants), accounted for part of the variance in total number of symptoms (38 and 17%, respectively), whereas none of the affective measures accounted for any of the variance in total number of sensitivities over all subjects; 4) after controlling for depression and anxiety, FSR still showed a trend toward poorer performance on a timed mental arithmetic task (p = 0.16); and 5) FSR and C showed opposite patterns of heart rate change to two different stressful tasks (mental arithmetic and isometric exercise) (group by task interaction, p < 0.05). The data are discussed in terms of a time-dependent sensitization (TDS) process that predicts a cross-sensitizing and cross-reactive role for xenobiotic agents (e.g., foods, chemicals, drugs, and inhalants) and for salient psychological stress in the expression of psychophysiological dysfunctions of FSR. As in other chronically ill populations, negative affect in food-sensitive individuals may explain greater symptom reporting, but not necessarily account for the illness itself. For either a food or a psychological stimulus to begin to elicit sensitized responses, e.g., marked physiological differences from C, FSR may require multiple, intermittent exposures spaced over 5-28 days rather than on only 1 day.

Effect of chronic estradiol and progesterone treatments of ovariectomized rats on brain dopamine uptake sites

Dopamine released from brain nerve terminals is mainly removed from the synaptic cleft by an uptake mechanism. Despite their functional importance, modulation of the dopamine uptake sites is still not well known. Steroid hormones were shown to modulate brain dopamine transmission. The aim of this study was thus to investigate in ovariectomized rats the effects of 17 beta-estradiol and progesterone treatments on brain dopamine uptake sites. Treatments consisted of 17 beta-estradiol (10 micrograms/0.2 ml), progesterone (0.72 mg/0.2 ml), 17 beta-estradiol + progesterone, or the vehicle (0.3% gelatin in saline solution) twice daily for 2 weeks. The steroid treatments left the affinity of [3H]GBR 12935 binding to striatal homogenates unchanged (ovariectomized rats, 0.823 +/- 0.028 nM), whereas the density was increased by these steroids alone or in combination to a similar extent of 16-23%. Chronic treatment of ovariectomized rats with 17 beta-estradiol, progesterone, or their combination increased to the same extent and uniformly [3H]-GBR 12935 binding in the striatum as measured by autoradiography; the increase was similar in the substantia nigra pars compacta, whereas no steroid effect was observed in the nucleus accumbens and in the substantia nigra pars reticulata. In summary, chronic exposure to 17 beta-estradiol and/or progesterone increased dopamine uptake site density in the nigrostriatal dopaminergic system, whereas the nucleus accumbens and the substantia nigra pars reticulata were unaffected.

Behavioral and neurochemical changes caused by repeated ethanol and cocaine administration

Combined cocaine and ethanol abuse has become increasingly popular, yet research on the behavioral and neurochemical interactions of these two substances is limited. Four groups of male rats received either daily cocaine (10 mg/kg, IP) or saline injections with either water (groups C and S) or only 15% ethanol to drink (groups CE and E). Initially, locomotor activity was increased equally by ethanol or cocaine and to the greatest extent by both. After 2 weeks of drug treatment, group C exhibited behavioral sensitization to cocaine, group E exhibited ethanol tolerance and group CE exhibited greater cocaine sensitization with no indication of ethanol tolerance. In support of enhanced sensitization to cocaine, amphetamine-stimulated 3H-dopamine (DA) release in striatum and D2 DA receptor binding in the nucleus accumbens (NAC) were increased in group CE compared to group C. In support of a loss of ethanol tolerance, increases in striatal D2 DA and 35S-TBPS binding seen in group E (which exhibited ethanol tolerance) were absent in group CE (which did not exhibit tolerance). Thus, the synergistic effect of ethanol and cocaine on behavior may be due to complex interactions of these two drugs both on DA and GABA transmission in mesolimbic and nigrostriatal areas.

Cocaine in utero enhances the behavioral response to cocaine in adult rats

The effects of cocaine exposure in utero on cocaine-induced behaviors and dopamine (DA) transmission in the nigrostriatal and mesolimbic pathways were measured in adult rats. Pregnant rats received either saline or cocaine (1 or 3 mg/kg, IV) daily throughout gestation. When offspring were 3 months of age, locomotor and stereotypic behaviors were rated after an injection of either saline or cocaine (10 mg/kg, IP). Cocaine in utero increased the response to cocaine in adult offspring and increased basal locomotion in female offspring. Cocaine in utero increased amphetamine-stimulated release in female offspring but decreased release in males. On the other hand, male rats that had received cocaine in utero exhibited greater basal tritium release. One injection of cocaine increased amphetamine-stimulated [3H]DA release from striatal slices of male rats but not female rats. Neither cocaine in utero nor in vivo affected D2 DA receptor binding in striatum nor nucleus accumbens. Thus, cocaine in utero behaviorally sensitized animals to subsequent cocaine exposure and increased [3H]DA release from nigrostriatal endings, but the relationship of these two variables depended upon gender.