Luciana P. Cadore

Hypothalamic paraventricular nucleus modulates maternal aggression in rats : Effects of ibotenic acid lesion and oxytocin antisense

Central oxytocin (OT) appears to be crucial for maternal behavior. OT, through the parvocellular neurons of the hypothalamic paraventricular nucleus (PVN), can exert its physiological and behavioral effects by acting on OT receptors in nonpituitary projections of the PVN. The purpose of the present study was to analyze the role of the PVN and OT on maternal aggressive behavior in two different periods after delivery: on the fifth day (period of high aggressiveness) and on the eighteenth day postpartum (period of low aggressiveness). In the first experiment, ibotenic acid was injected into the PVN in order to lesion the parvocellular neurons. A second experiment was designed to study more specifically the effects of OT using the antisense technique. On the fifth day postpartum, both the PVN lesion by the ibotenic acid and a possible acute reduction of OT synthesis by the antisense administration in that nucleus increased maternal aggressive behavior, while on the eighteenth day postpartum no effect was recorded. We may conclude that central projections of the PVN modulate maternal aggression during a restricted period after delivery, only when lactating females show naturally high levels of aggressive behaviors.

Neuropsychological Performance in DSM-IV ADHD Subtypes: An Exploratory Study with Untreated Adolescents

Objective: To explore neuropsychological performance in untreated Brazilian adolescents suffering from attention-deficit hyperactivity disorder (ADHD). Method: We assessed 30 untreated adolescents with ADHD and 60 healthy control subjects, aged 12 to 16 years, using a neuropsychological battery including the Wisconsin Card-Sorting Test (WCST), the Stroop Test (ST), the Digit Span, and the Word Span. Results: We found neuropsychological differences among the DSM-IV ADHD subtypes. Adolescents with the predominantly inattentive subtype (ADHD-I) performed more poorly than did control subjects on both the Digit Span and the ST. On both the Digit Span and the WCST, adolescents with the combined subtype (ADHD-C) presented significantly more impairments than did control subjects. Adolescents with the predominantly hyperactive-impulsive type (ADHD-HI) did not differ significantly from the control subjects in any measure assessed, but had a better performance than did those with ADHD-C on both the Digit Span and the WCST. In addition, adolescents with ADHD-HI performed better on the ST than did adolescents with ADHD-I. Conclusions: These findings suggest cognitive differences among ADHD subtypes, supporting the diagnostic distinction among them. Adolescents with ADHD-HI do not seem to have significant cognitive deficits.

Long-lasting effects of neonatal stimulation on the behavior of rats.

The present study aimed to analyze the effects of neonatal stimulation on species-specific behaviors (defensive reactions to a predator and social interactions) in adult male and female rats. Handling and an unpredictable sequence of aversive stimuli were applied to male and female pups from the 1st to the 10th day after delivery; behavioral inhibition, aggression, and sexual behavior were evaluated in adulthood. Results showed that either neonatal handling or aversive stimulation decreased behavioral inhibition in a novel and potentially harmful situation (open field with a predator) in both male and female rats and increased maternal aggressive behavior. Sexual behavior in both males and females decreased, which could affect reproductive capability. The results could cast doubts on the generalization of beneficial effects of neonatal stimulation on the behavior of adult rats.

Low-dose adrenocorticotropin test in patients with the Acquired Immunodeficiency Syndrome

Adrenocortical insufficiency is a serious complication of AIDS. Usually, integrity of the hypothalamo-pituitary-adrenal (HPA) axis in AIDS patients is assessed by measuring basal cortisol levels and cortisol response to 250 microg of ACTH. Recent studies suggest that a lower ACTH dose increases the sensitivity of the procedure. In the present study, we investigated the prevalence of adrenal hypofunction in AIDS patients using a low-dose ACTH test (1 microg), evaluated the clinical characteristics that might suggest this diagnosis, and the diseases and/or drugs that could be associated with it. We prospectively evaluated 63 very ill AIDS patients and 16 normal controls. A standard examination assessed the presence of signs and symptoms of adrenal insufficiency. Blood samples were collected before and 30 and 40 minutes after an injection of 1 microg 1-24 ACTH. No opportunistic disease, signs, symptoms or drugs were associated with an abnormal cortisol response to ACTH. The lowest stimulated cortisol level in the control group was 18.5 microg/dL; cortisol levels > or = 18 microg/dL were taken to indicate a normal HPA axis. Test results revealed that 12/63 AIDS patients (19%) had an abnormal HPA axis. With these data in mind, we suggest a prospective adrenal function evaluation of all severely ill AIDS patients.

Aversive stimulation during the stress-hyporesponsive period does not affect the number of corticotroph cells in neonatal male rats

Immunohistochemistry was used to evaluate the effects of neonatal handling and aversive stimulation during the first 10 days of life on the number of corticotrophs in the anterior lobe of the pituitary of 11-day-old male Wistar rats. Since adult rats handled during infancy respond with reduced corticosterone secretion in response to stressors and with less behavior inhibition in novel environments, we assumed that neonatal stimulation could affect pituitary morphology during this critical period of cell differentiation. Three groups of animals were studied: intact (no manipulation, N = 5), handled (N = 5) and stimulated (submitted to 3 different aversive stimuli, N = 5). The percentage of ACTH-immunoreactive cells in the anterior lobe of the pituitary (number of ACTH-stained cells divided by total number of cells) was determined by examining three slices per pituitary in which a minimum of 200 cells were counted by two independent researchers. Although animals during the neonatal period are less reactive to stress-like stimulation in terms of ACTH and corticosterone secretion, results showed that the relative number of ACTH-stained cells of neonatal handled (0.25 +/- 0.01) and aversive stimulated (0.29 +/- 0.03) rats was not significantly different from intact (0.30 +/- 0.03) animals. Neonatal stimulation may have a differential effect on the various subpopulations of corticotroph cells in the anterior pituitary.