Effects of neonatal treatment with cyproterone acetate on aggressive behavior induced by footshock in adult male rats

High levels of androgens are required to organize aggressive behavior in adult male rats. Footshock-induced aggression was tested in Wistar rats allocated to one of three experimental groups: control (oil-injected) males (M), males neonatally injected with the antiandrogen cyproterone acetate (CA), and males treated as in the CA group but gonadectomized just before puberty (CAG). An antiaggressive effect of CA in those adult male rats neonatally treated with this compound was found. Neonatal exposure to cyproterone acetate exerts an antiandrogenic effect over the expression of shock-induced aggressive behavior. The behavioral effects of CA were not countered by adult treatment with testosterone propionate.     

Memory impairments and hippocampal modifications in adult rats with neonatal isolation stress experience

Early life events have profound consequences. Our research demonstrates that the early life stress of neonatal isolation (1-h individual isolation on postnatal days 2-9) in rats has immediate and enduring neural and behavioral effects. Recently, we showed neonatal isolation impaired hippocampal-dependent context conditioned fear in adult rats. We now expand upon this finding to test whether neonatal isolation impairs performance in inhibitory avoidance and in the non-aversive, hippocampal-dependent object recognition task. In addition to assessments of hippocampal-dependent memory, we examined if neonatal isolation results in cellular alterations in the adult hippocampus. This was measured with antibodies that selectively label calpain-mediated spectrin breakdown product (BDP), a marker of cytoskeletal modification that can have neuronal consequences. Neonatally isolated male and female rats showed impaired performance in both memory tasks as well as elevated BDP levels in hippocampal immunoblot samples. In tissue sections stained for BDP, the cytoskeletal fragmentation was localized to pyramidal neurons and their proximal dendrites. Interestingly, the hippocampal samples also exhibited reduced staining for the postsynaptic marker, GluR1. Neonatal isolation may render those neurons involved in memory encoding to be vulnerable to calpain deregulation and synaptic compromise as shown previously with brain injury. Together with our prior research showing enhanced striatal-dependent learning and neurochemical responsivity, these results indicate that the early experience of neonatal isolation causes enduring yet opposing region-specific neural and behavioral alterations.     

Male-female differences and the influence of neonatal and adult testosterone on intraspecies aggression in rats.

Male and female albino rats were tested for intraspecies aggression without the use of shock. In the first experiment, male pairs showed more biting attacks, offensive sideways movements, and self-grooming than did female pairs; male pairs also showed more stereotyped defensive/submissive behaviors and were wounded more frequently. The second experiment examined the effects of neonatal castration and testosterone propionate (TP) administration on fighting. Males castrated at birth attacked other males less frequently than did controls when tested with TP treatment as adults. The TP given at birth to neonatally castrated males restored attacks to control levels. Females given TP as neonates did not differ from either male or female controls. Other aggressive/defensive behaviors, however, did not show this pattern. The results suggest that while the presence of testosterone during a brief postnatal period and during adulthood is necessary for attack behavior to occur, other related behaviors may not be affected in a similar manner.     

Glucose treatment reduces memory deficits in young adult rats fed high-fat diets

Feeding rats high-fat diets for 3 months produces a widespread cognitive deficit that affects performance on a wide range of learning and memory tasks. The present study tested the hypothesis that this effect is related to a fat-induced impairment in glucose metabolism. Following 3 months of dietary intervention (20% by weight fat diets, composed primarily of either beef tallow or soybean oil versus standard laboratory chow), male Long-Evans rats were tested on a variable interval delayed alternation (VIDA) task that measures learning and memory functions that differentially involve specific brain regions. Relative to rats fed chow, rats consuming the high-fat diets were impaired on all aspects of VIDA performance. Following baseline testing, rats were maintained on their respective diets and the effect of glucose administration (100 mg/kg BW; i.p.) was examined. For the next 6 days, animals alternately received injections of saline or glucose 30 min prior to VIDA testing. Glucose treatment improved performance, with the effect being most pronounced at the longer intertrial intervals where task performance is sensitive to hippocampal impairment. Importantly, the beneficial effect of glucose were confined to those animals consuming the high-fat diets and were not observed in rats fed chow. These results demonstrate that glucose administration can overcome those deficits associated with hippocampal function in rats fed high-fat diets and are consistent with the hypothesis that high-fat diets, in part, mediate their effect through the development of insulin resistance and glucose intolerance.     

Organisational effects of neonatal and pubertal testosterone on sexually differentiated behaviours in the open-field and head-dip apparatus

On days 1 and 4 after birth rats were injected with 100 μg of testosterone propionate (TP) or vehicle, and at 35 days of age they were injected intramuscularly with 400 μg of testosterone oenanthate (TO), a long acting androgen, or the vehicle. There were four groups (oil-oil, TP-oil, oil-TO, TP-TO), each group subdivided by sex. Females treated with testosterone neonatally or at puberty were masculinised or defeminised on adult open-field behaviours, being less active and rearing less than oil-oil females; the oil-TO group also defaecated significantly more than controls. The TP-TO female group was indistinguishable from the oil-TO group. In a second experiment, sex differences were found in head-dipping behaviour as well as in activity and rearing. Females treated with TP or TO reared less and defaecated more than controls, and TP also decreased activity, but neither hormone treatment affected head-dipping behaviour. There is thus a peripubertal as well as a neonatal period when testosterone can act organisationally to masculinise or defeminise female rats. Potentiation between effects of neonatal and pubertal androgens was found on female body weights. TO alone had no effect, but TP-TO females were significantly heavier than controls at 90 days of age and by 130 days of age the TP-oil group was also heavier than controls.     

Psychosocial effects associated with dental fear in adult dental patients with avoidance behaviours

Abstract

The most obvious consequence of a genuine dental phobic reaction is the avoidance of necessary dental care. Previous research has indicated that such avoidance has adverse effects on an individual's oral health status, and also reduces the quality of life. However, systematic investigations in this area of dentistry are few and clinical observations and interviews may often fail to elicit information regarding the impairment created outside the dental situation. The present investigation assessed the presence and levels of emotional and social life effects among dental phobic patients with regard to the prevalence of dental and general fears and the length of time for which dentistry had been avoided. It was shown that a majority of the patients felt that they had to curtail their social relations, and many, especially long-term avoiders, reported wide-spread negative social life effects. Often this had extended into feelings of loneliness or to overt social isolation. It remains to be seen whether fear of dentistry itself produces disadvantage or whether these effects are mainly related to personality factors, which can also promote the development of dental fear. Alternatively, poor dental health, which is probably more frequent in anxious patients, may be perceived by these patients and thus impair social relationships.     

Potentiation and overshadowing in preweanling and adult rats

Four experiments compared the aversion acquired by 18-day-old and 60-day-old rats to a flavor that was either tasted alone or in combination, simultaneously or successively, with another flavor when paired with illness. The purpose was to study temporal variables and theoretical issues pertinent to potentiation and overshadowing while investigating ontogenetic differences in these phenomena. When either the preweanlings or the adults were presented a simultaneous compound flavor (sucrose/coffee) followed by lithium chloride-induced illness, greater sucrose aversions were found than for animals conditioned on sucrose alone--that is, potentiation. Preweanlings demonstrated greater potentiation than did adults, whether the conditioned stimulus-unconditioned stimulus (CS-US) delay was 0 or 1 hr. This potentiation was eliminated by nonreinforced presentations of the alternative CS element. Potentiation was not seen when the two flavors were presented successively as the CS; instead, overshadowing occurred. Tests of configuring by extinction procedures indicated a tendency for these animals to form a configured representation of the simultaneous compound solution. This disposition for configuring tended to be more pronounced for preweanlings than for adults. Ontogenetic differences in response to configuration, CS saliency, and generalization decrement seem consistent with at least one model of potentiation and the ontogenetic differences in potentiation seen in the present experiments.