Susana T. Broitman

Effects of a histamine synthesis inhibitor and antihistamines on the sexual behavior of female rats

Intraventricular administration of α-hydrazinohistidine, a histamine synthesis inhibitor, at different doses and times before testing produced a significant decrease of lordotic responses and sexual receptivity in ovariectomized estrogen plus progesterone-primed female rats. The H1-antihistamines pyrilamine and chlorfeniramine and the H2-antihistamine metiamide, injected in the lateral ventricle, significantly decreased the lordosis quotient but did not modify receptivity; antihistamine-injected rats showed no soliciting behavior. Exploratory activity was decreased by both α-hydrazinohistidine and metiamide but not by the H1-antihistamines. It is concluded that treatments which either deplete histamine or block their receptors can alter female copulatory responsiveness. The mechanism of this antihistamine effect appears to be unrelated to that of other side effects, such as motor impairment, sedation, or local anesthesia.

Effects of chronic imipramine and clomipramine oral administration on maternal behavior and litter development

The effects of the oral administration of imipramine (IM) or clomipramine (CIM) in adult female rats before pregnancy or during nursing were evaluated. IM caused a significant decrease of body weight in both groups of animals and affected the body weight of litters when administered during nursing. CIM reduced the increase of weight in the mothers throughout the experiment. Both IM and CIM decreased water and food intake and locomotor activity of the adult rats. Rats treated during nursing with IM showed decreased maternal behavior at various times of treatment. The milk intake of pups from drug-treated mothers also decreased. Pup eyeopening was delayed by CIM both before pregnancy and during nursing and by IM treatment during nursing. Vaginal opening was retarded in female litters from mothers treated during nursing. Openfield behavior showed modifications at 60 days of age in male pups from mothers exposed to IM during nursing.Results indicate that the two tricyclic drugs were able to produce general and behavioral modifications in both mothers and their litters. These modifications seem to depend on whether the drug is given before pregnancy or during nursing. Control experiments in dams fed with a restricted diet suggest that the observed alterations in maternal behavior and litter development is not due to the undernourishment caused by drug administration.

Locomotor activity and regional brain noradrenaline levels in rats treated with prenylamine

Ratas inyectadas con diferentes dosis de prenylamina (gluconato) presentaron una marcada disminución de la actividad motora espontánea y de los niveles de noradrenalina en el hipotálamo, tálamo y corteza cerebral, pero no en el tegmento del mesencéfalo. Se detectó una estrecha relación entre la caída de la concentración de NA hipotalámica y la disminución de la actividad espontanea con las diferentes dosis de prenylamina empleadas.

Effect of prenatal and postnatal exposure to therapeutic doses of chlorimipramine on emotionality in the rat

Prenatal administration of high doses of tricyclic antidepressants have been reported to produce teratogenic and behavioral effects in rat offspring. In the present work, behavioral abnormalities are described in offspring of rats treated with therapeutic doses of chlorimipramine (CIM) during pregnancy (CIM-P), lactation (CIM-L) and during the whole pregnancy-lactation period (CIM-PL). CIM-P treatment did not produce teratogenic effects, did not affect number or body weight of pups at birth and did not induce neonatal mortality. At 2 months of age, the CIM-P males showed a significant increase in digging and grooming (familiar environment test), a decrease in “exploration” (novel environment test) and a decrease in active social interactions (social behavior test). Females were more resistant than males to the prenatal CIM treatment. The results suggest increased emotionality in CIM-P pups. Some behavioral abnormalities were also observed in the tests performed at 4 months of age. CIM-L treatment had minor effects on litter behavior. CIM-PL treatment potentiated the effects of the CIM-P treatment. In the CIM-PL males, impairment of exploration of a novel environment still remained in the tests performed at 4 months of age. It is speculated that when prenatal brain development is altered by CIM, further postnatal treatment may impair compensatory processes occurring in early postnatal life.

Preferential nesting in lemon-scented environment in rats reared on lemon-scented bedding from birth to weaning

Newborn rats (males and females) were reared on lemon scented shavings from birth to weaning. The experienced rats (111 animals) and their controls (135 animals) were tested for lemon odor preference at 21, 51, 81, 111 and 141 days of age. The test box consisted of two preference chambers, containing wood shavings, interconnected by a starting compartment. Shavings of one of the preference chambers were sprinkled with natural lemon juice. The preference ratio was obtained on the basis of the chamber selected for nesting. The results clearly show that (1) sex differences occur in both experienced and control groups of rats and (2) rats reared on lemon scented bedding from birth to weaning acquire a permanent preference for nesting in the lemon scented chamber. The results are consistent with the hypothesis that an imprinting-like process takes place.

Effect of serotonergic and catecholaminergic antagonists on mild-stress-induced excessive grooming in the rat

Excessive grooming was induced in male rats by two ip injections of physiological saline. This mild stressful procedure did not modify open-field locomotion in 5-min trials. Methysergide (15 mg/kg) and pizotifene (5 mg/kg), serotonergic blockers, selectively prevented the grooming response to saline without affecting locomotion. Haloperidol (.4 mg/kg) also prevented the excessive grooming. However, this dopaminergic blocker impaired locomotion. The alpha- or beta-adrenoceptor antagonists phentolamine (20 mg/kg) and l-propranolol (20 mg/kg) did not prevent the excessive grooming in response to saline and did not affect locomotion. The results suggest that some serotonergic pathways in the brain are involved in the grooming response to a mild stress and support previous findings on the role of dopaminergic systems on this activity.

Maternal and sex-related influences on locomotor activity in rats following weaning

Abstract The effect of the presence of the mother beyond the normal time of weaning on the locomotor activity of litters is evaluated in the present work. Weaned rats, either females or males, showed a significantly higher activity in the open-field arena than the non-weaned ones. A sex-related difference was also detected. Weaned and nonweaned females showed higher activity than the weaned and nonweaned males, respectively. The androgen-induced lowering of female activity is affected by the presence of the mother. This is substained by the fact that weaned androgenized females exhibited higher levels of activity than nonweaned androgenized females. Our observations suggest that the presence of the mother after the normal time of weaning disturbs the emotional maturation of litters.

Effects of the chronic ingestion of therapeutic doses of chlorimipramine on the behavioral action of agonists and antagonists of serotonin in male rats

Locomotor activity and hole-board exploration (frequency and time spent head-dipping) were impaired in male rats by injecting IP the 5-HT agonists, fluoxetine and 5-HTP. This treatment produced also myoclonus and increased the time spent resting during trials. The chronic ingestion of chlorimipramine (CIM) or the injection of the 5-HT receptor blocker, methysergide (15 mg/kg) prevented the action of the 5-HT agonists on locomotion and resting and blocked the appearance of myoclonus. Both CIM and methysergide prevented to a minor degree the fluoxetine-5-HTP-induced decrease of exploration. The chronic ingestion of CIM clearly potentiated the effects of methysergide on hole-board exploration. Results suggest that the chronic treatment with therapeutic doses of CIM reduces the functional activity of some 5-HT systems in the brain of the rat, probably by blockade of post-synaptic 5-HT receptors. This does not preclude, however, that CIM may also alter some NA systems.

Behavioral responses of high and low active male rats to the chronic ingestion of desipramine.

Male rats arbitrarily selected for high and low motor activity (HA and LA-rats) were submitted to the chronic ingestion (30 days) of desipramine (DSP) in doses of about 1.5, 3 and 6 mg/kg/24 hr. Their motor activity was assessed in an animal activity monitor providing a measure of total horizontal movements and vertical movements and in a hole-board providing a measure of locomotion, head-dipping and grooming. There were significant differences between HA and LA-rats in their behavioral response to DSP treatment. At the doses used DSP did not affect horizontal and vertical movements and hole-board locomotion or exploration in HA-rats (Experiment 1). In LA-rats, however (Experiment 2), these motor activities were significantly stimulated by DSP. Such effect was dose dependent; 1.5 mg/kg/24 hr was ineffective while 6 mg/kg/24 hr produced a clear cut reversion of hypoactivity. It is speculated that DSP treatment increased resistance of LA-rats to the mild stress caused by testing.