Environmental enrichment attenuates nicotine behavioral sensitization in male and female rats.

Environmental enrichment decreases nicotine reactivity in male rats, but these effects have not been examined in females. This research was conducted to examine the effects of enrichment on nicotine behavioral sensitization (i.e., nicotine reactivity) in male and female rats. One hundred forty-four Sprague-Dawley rats (72 male, 72 female) were raised in isolation, social enrichment (groups of three rats [SE]), or combined physical enrichment and social enrichment (groups of three rats with novel toys [PESE]) housing conditions. As adults, they received daily subcutaneous injections of saline or nicotine (0.1, 0.5, or 1.0 mg/kg) for 12 days; locomotor activity was measured on drug days 1, 5, 9, and 12. Before drug administration, PESE and SE decreased activity in males; only PESE decreased activity in females, F(2, 120) = 6.51, p < .01. In the drug phase, nicotine behavioral sensitization occurred, F(8.46, 341.04) = 20.71, p < .001, and was greater in females than males, F(8.340, 319.715) = 2.072, p < .05. Enrichment decreased nicotine behavioral sensitization in both sexes, F(16.91, 341.04) = 2.48, p < .01. In conclusion, nicotine behavioral sensitization occurred in male and female rats and was attenuated by environmental enrichment. This research has implications for treatment and prevention strategies in humans. Programs that incorporate aspects of social and environmental stimulation may have enhanced effectiveness in preventing and reducing cigarette smoking and may have implications for relapse prevention.

Psychological adjustment in children and families living with HIV.

OBJECTIVE: To assess psychological adjustment in children living with human immunodeficiency virus (HIV) and their primary caregivers. METHODS: The study protocol included use of standardized questionnaires to assess emotional and behavioral health of 57 children and 54 caregivers (Phase 1). Positive screening led to standardized interviews to assess current psychiatric diagnoses (Phase 2). RESULTS: Of the 16 children who entered Phase 2, 6 (38%) met the criteria for a psychiatric diagnosis. Of the 15 adults who met the screening criteria, 13 completed a computerized psychiatric interview and all 13 (100%) met the criteria for a psychiatric diagnosis. CONCLUSIONS: While important mental health needs were identified in families with HIV, the majority of families did not exhibit mental health disorders. These results might reflect the substantial psychosocial resilience of these families. Further study is needed to determine to what extent the mental health needs of children and their caregivers are being met. In addition, identification of protective factors in resilience and coping in families living with a chronic illness is warranted.

Effects of social and physical enrichment on open field activity differ in male and female Sprague-Dawley rats.

Environmental enrichment affects performance of neurologically intact organisms and facilitates recovery of function following CNS injury. Only, a few recent studies have examined the extent to which physical versus social aspects of enriched environments separately contribute to superior performance [Pietropaolo S, Branchi I, Cirulli F, Chiarotti F, Aloe L, Alleva E. Long-term effects of the periadolescent environment on exploratory activity and aggressive behavior in mice: social vs. physical enrichment. Physiol Behav 2004;81:443-53; Schrijver NC, Bahr NI, Weiss IC, Wurbel H. Dissociable effects of isolation rearing and environmental enrichment on exploration, spatial learning and HPA activity in adult rats. Pharmacol Biochem Behav 2002;73:209-24] or the extent to which male and females differ in their response to enrichment [Bardo MT, Kiebaur JE, Valone JM, Deaton C. Environmental enrichment decreases intravenous self-administration of amphetamine in male and female rats. Psychopharm 2001;155:278-84; Daniel JM, Roberts S, Dohanich G. Effects of ovarian hormones and environment on radial maze and water maze performance of female rats. Physiol Behav 1999;66:11-20]. The current experiment examined the separate and combined effects of social enrichment (SE) and physical enrichment (PE) on locomotor activity of male and female Sprague-Dawley rats to determine what aspect of enrichment had the greatest effect to alter activity and to determine whether there were sex differences in these effects. Habituation in the open field was used as an index of simple information-processing and refers to the decrease in activity over time that occurs as an animal becomes acclimated to its environment. Faster habituation indicates greater information-processing. The major findings from the current study were: (1) social enrichment has the greatest effect to improve performance (i.e., increased habituation) for both males and females and (2) the effects of enrichment overall generally appear to be greater for males than for females.

Adolescent and adult female rats differ in sensitivity to nicotine's activity effects.

More than 90% of cigarette smokers begin smoking during adolescence. This between-subjects repeated-measures experiment examined: (1) nicotine's acute effects on activity in adolescent and adult female Sprague-Dawley rats (Drug Phase I); (2) the effects of age of initial nicotine exposure on activity when nicotine was not administered (Interim Phase); and (3) the effects of age of initial nicotine exposure on later responses to nicotine (Drug Phase II). The experiment consisted of three separate phases. In Drug Phase I, animals were administered either 0 (saline), 0.01, 0.10, 0.50, or 1.0 mg/kg nicotine via subcutaneous injections for 12 days and horizontal activity was measured daily. During the Interim Phase (no drug phase), activity was measured but nicotine was not administered. During Drug Phase II, the same animals were administered the same nicotine dosages as in Drug Phase I for 12 days and activity was measured daily. Drug Phase I revealed dose-response differences between adolescent and adult female rats. In addition, animals initially exposed to nicotine in adolescence exhibited greater sensitivity to nicotine's activity-increasing effects than did females initially exposed to nicotine in adulthood (i.e., Drug Phase II).

Effects of nicotine on elevated plus maze and locomotor activity in male and female adolescent and adult rats.

Over 4500 adolescents start smoking every day in the United States. Of these, one-third will die prematurely from smoking-related diseases. The current experiment examined the effects of repeated-acute nicotine administration (saline, 0.1, 0.5, or 1.0 mg/kg daily) on elevated plus maze (EPM) and locomotor behaviors of 160 adolescent and adult male and female Sprague-Dawley rats. Nicotine's effects depended on age and sex of animal. On the EPM, nicotine exerted anxiolytic effects (increased percentage of time in the open arms) in adolescent males, but exerted anxiogenic effects (decreased percentage of time in the open arms) in adolescent females and in adult males and females. For adults, peak locomotor activity occurred at the 0.5-mg/kg dosage, and the 1.0-mg/kg dosage reduced activity below the saline level on Day 1 and below the 0.5-mg/kg level on Days 1, 3, and 5. For adolescents, peak locomotor activity occurred at the 1.0-mg/kg dosage and there were no activity-depressant effects. These findings suggest there are age differences in sensitivity to nicotine that may affect vulnerability to long-term tobacco use.

Effects of nicotine on heart dimensions and blood volume in male and female rats.

The adverse effects of tobacco smoking on the cardiovascular system are well established. Effects of nicotine on the heart, in contrast, are not well characterized. Understanding specific effects of nicotine on the heart and on blood volume is relevant to (a) elucidating the mechanisms by which nicotine may contribute to heart disease and (b) determining potential risks associated with nicotine products used in smoking cessation or to treat various medical conditions. The present experiment investigated effects of continuous nicotine administration for 14 days (0, 6, or 12 mg/kg/day) on heart histopathology and blood volume (a measure of hemoconcentration) in 59 male and 59 female rats of two strains (Sprague-Dawley and Long-Evans). Following nicotine administration, animals were sacrificed and blood volume was measured. Heart length; heart weight; left ventricle, right ventricle, lateral wall, anterior wall, and posterior wall thicknesses; and intraventricular width (i.e., septum) were measured. Nicotine reduced heart weight, heart length, and overall blood volume. Females were more sensitive than males to the effects of nicotine on heart weight. In contrast, males were more sensitive than females to the effects of nicotine on heart length. Together, these findings suggest that males and females differ in their sensitivity to nicotine's cardiac effects.

Adolescent and adult male rats differ in sensitivity to nicotine's activity effects.

More than 90% of cigarette smokers begin smoking during adolescence, suggesting that adolescents may be particularly vulnerable to nicotine's effects. This experiment examined: (1) nicotine's acute effects on locomotion in adolescent and adult male Sprague-Dawley rats (Drug Phase I); (2) the effects of age of initial nicotine exposure on locomotion when nicotine was not administered (Interim Phase); and (3) the effects of age of initial nicotine exposure on later responses to nicotine (Drug Phase II). In Drug Phase I, animals were administered 0, 0.01, 0.10, 0.50, or 1.0 mg/kg nicotine sc for 12 days and horizontal activity was measured daily. During the Interim Phase, activity was measured but nicotine was not administered. During Drug Phase II, animals were administered the same nicotine dosages as in Drug Phase I for 12 days, and activity was measured daily. Drug Phase I revealed dose-response differences between adolescents and adults such that adolescents exhibited peak activity at both the 0.50- and 1.0-mg/kg dosages, but adults exhibited peak activity at the 0.50-mg/kg dosage. Initial nicotine exposure in adolescence (0.50 and 1.0 mg/kg), but not in adulthood, resulted in hyperactivity in adulthood in the absence of nicotine (Interim Phase). Reexposure to nicotine when all animals were adults (Drug Phase II) revealed that initial nicotine exposure in adolescence compared to adulthood resulted in dose-response differences in adulthood similar to those in Drug Phase I. In addition, animals initially exposed in adolescence exhibited sensitization to nicotine's activity-increasing effects in adulthood. These findings suggest that there are age differences in nicotine sensitivity that could predispose individuals initially exposed to nicotine in adolescence to long-term smoking.

Repeated acute stress alters heart morphometry in male and female rats differently.

Stress exerts deleterious effects on the cardiovascular system. Left ventricular hypertrophy has been identified as a risk factor for heart disease. The effects of stress on other heart parameters, including heart size and heart shape, are not well-characterized. In addition, the extent to which males and females differ in stress effects on these measures has not been examined, but may help to further explain gender differences in heart disease morbidity and mortality. The present experiment examined effects of mild daily stress on heart morphology and blood volume (obtained by ex-sanguination at decapitation) in 39 male and 40 female rats of two strains. Following 14 days of stress exposure, rats were killed and blood volume was measured. Heart length, heart weight, left ventricle cavity width, right ventricle width, lateral wall thickness, anterior wall thickness, posterior wall thickness, and septal wall thickness were measured. In males, after controlling for body weight, stress decreased heart length and left ventricle cavity width and increased septal wall thickness. In females, after controlling for body weight, stress reduced total blood volume, but did not significantly affect other heart parameters. These findings suggest that stress exposure can alter heart morphology and blood volume and that there are sex differences in these effects.