The expression of an intraspecific aggressive reaction in the face of a stressor agent alters the immune response in rats

A repercussão sobre a resposta imune da expressão da agressividade intra-específica diante de um estressor foi investigada em ratos. Aos 90 dias de vida, os animais foram divididos em três grupos: grupo-controle (foram realizadas apenas mensurações imunológicas), choque nas patas (FS) (os animais receberam FS individualmente) e grupo resposta agressiva intra-específica (IAR) (os animais receberam FS e apresentaram IAR). Para as medições imunológicas, amostras de sangue foram coletadas imediatamente, 7 e 15 dias após FS ou IAR. O FS reduziu a quantidade total de leucócitos. Contudo, a agressividade foi acompanhada, além da redução do número de leucócitos, por diminuição de linfócitos e aumento de neutrófilos. Além disso, também foi observada elevação no número de leucócitos associada a aumento na resposta imune humoral uma semana após as IAR. Neste estudo, a expressão da agressividade intra-específica diante de um estressor parece ativar o sistema imune e potencializar a resposta humoral antígeno específica.

Neonatal administration of citalopram delays somatic maturation in rats

We investigated the somatic maturation of neonate rats treated during the suckling period with citalopram, a selective serotonin reuptake inhibitor. Groups with 6 male neonates were randomly assigned to different treatments 24 h after birth. Each litter was suckled by one of the dams until the 21st postnatal day. Body weight, head axis and tail length were measured daily from the 1st to the 21st postnatal day. Time of ear unfolding, auditory conduit opening, incisor eruption, and eye opening was determined. Pups received 5 mg (Cit5), 10 mg (Cit10) or 20 mg/kg (Cit20) citalopram sc, or saline (0.9 percent NaCl, w/v, sc). Compared to saline, body weight was lower (24.04 percent, P < 0.01) for Cit10 from the 10th to the 21st day and for Cit20 from the 6th to the 21st day (38.19 percent, P < 0.01). Tail length was reduced in the Cit20 group (15.48 percent, P < 0.001) from the 8th to the 21st day. A reduction in mediolateral head axis (10.53 percent, P < 0.05) was observed from the 11th to the 21st day in Cit10 and from the 6th to the 21st day in Cit20 (13.16 percent, P < 0.001). A reduction in anteroposterior head axis was also observed in the Cit20 group (5.28 percent, P < 0.05) from the 13th to the 21stday. Conversely, this axis showed accelerated growth from the 12th to the 21stday in the Cit5 group (13.05 percent, P < 0.05). Auditory conduit opening was delayed in the Cit5 and Cit20 groups and incisor eruption was delayed in all citalopram groups. These findings show that citalopram injected during suckling to rats induces body alterations and suggest that the activity of the serotoninergic system participates in growth mechanisms.

Reduction of intraspecific aggression in adult rats by neonatal treatment with a selective serotonin reuptake inhibitor

Most studies suggest that serotonin exerts an inhibitory control on the aggression process. According to experimental evidence, this amine also influences growth and development of the nervous tissue including serotoninergic neurons. Thus, the possibility exists that increased serotonin availability in young animals facilitates a long-lasting effect on aggressive responses. The present study aimed to investigate the aggressive behavior of adult rats (90-120 days) treated from the 1st to the 19th postnatal day with citalopram (CIT), a selective serotonin reuptake inhibitor (20 mg/kg, sc, every 3 days). Aggressive behavior was induced by placing a pair of rats (matched by weight) in a box (20 x 20 x 20 cm), and submitting them to a 20-min session of electric footshocks (five 1.6-mA - 2-s current pulses, separated by a 4-min intershock interval). When compared to the control group (rats treated for the same period with equivalent volumes of saline solution), the CIT group presented a 41.4 percent reduction in the duration of aggressive response. The results indicate that the repeated administration of CIT early in life reduces the aggressive behavior in adulthood and suggest that the increased brain serotoninergic activity could play a role in this effect