Adrenergic receptor ß3 is involved in the memory consolidation process in mice

Attention and emotion have a positive impact on memory formation, which is related to the activation of the noradrenergic system in the brain. The hippocampus and amygdala are fundamental structures in memory acquisition, which is modulated by noradrenaline through the noradrenergic receptors. Pharmacological studies suggest that memory acquisition depends on the action of both the β3 (β3-AR) and β2 (β2-AR) receptor subtypes. However, the use of animal models with specific knockout for the β3-AR receptor only (β3-ARKO) allows researchers to more accurately assess its role in memory formation processes. In the present study, we evaluated short- and long-term memory acquisition capacity in β3-ARKO mice and wild-type mice at approximately 60 days of age. The animals were submitted to the open field test, the elevated plus maze, object recognition, and social preference. The results showed that the absence of the β3-AR receptor caused no impairment in locomotion and did not cause anxious behavior, but it caused significant impairment of short- and long-term memory compared to wild-type animals. We also evaluated the expression of genes involved in memory consolidation. The mRNA levels for GLUT3, a glucose transporter expressed in the central nervous system, were significantly reduced in the amygdala, but not in the hippocampus of the β3-ARKO animals. Our results showed that β3-AR was involved in the process of acquisition of declarative memory, and its action may be due to the facilitation of glucose absorption in the amygdala.

Antinociceptive and anti-inflammatory effects of Lantana camara L. extract in mice / Efeitos antinociceptivos do extrato de Lantana camara L. em camundongos

ABSTRACT: he Lantana camara L. belongs to the family Verbenaceae, which contains several active compounds in leaves and roots and which are reported to have medicinal and insecticidal properties. Studies of plants within the same family show the existence of anti-inflammatory activity in paw edema induced by carrageenan, serotonin and histamine and analgesic activity in the acetic acid writhing and tail-flick tests. The present study investigated whether the L. camara extract (ACE) also exerts these effects. The ACE toxicity was studied in male mice, and the percentage of mortality recorded 7 days after treatment was assessed. The ACE was evaluated as an antinociceptive agent in the hot plate, tail-flick and acetic acid writhing tests at a nontoxic dose of 1.0 g/Kg. The results showed that 1.5 g/Kg of ACE was not able to cause death, and doses of 3.0 and 4.0 g/Kg caused 50% and 60% death, respectively, in male mice. In all of the antinociceptive tests, 1 g/Kg of ACE markedly reduced responses to pain. Our findings suggest that ACE may have active anti-inflammatory and antinociceptive properties in much smaller doses than toxic.

RESUMO: Lantana camara L. pertence à família Verbenaceae, a qual contem muitos princípios ativos em suas folhas e raízes com propriedade medicinais e inseticidas. Estudos com plantas da mesma família mostram a existência de propriedades antinflamatórias no modelo de edema de pata induzido pela carragenina, serotonina e histamina, além da atividade analgésica nos testes de contorção induzida pelo ácido acético e da retirada da cauda por estímulo térmico. O presente trabalho investigou os efeitos tóxicos e antinociceptivos do extrato de L. camara (ACE) em camundongos. Para tanto, investigou-se a porcentagem de mortes em 7 dias após a administração de diferentes doses do extrato. Avaliou-se também os efeitos antinociceptivos do ACE pelos testes da placa quente, estimulação térmica da cauda e contorções abdominais induzidas pelo ácido acético com a dose não-tóxica [1,0 g/Kg]. Os resultados mostraram que 1,5 g/Kg do ACE não causou mortalidade, enquanto que 3,0 e 4,0 g/Kg promoveram 50 e 60% de mortalidade, respectivamente. Em todos os testes antinociceptivos, a dose de 1,0 g/Kg do ACE reduziu a resposta à dor. Os presentes resultados indicam que o ACE apresenta propriedades antinflamatórias e analgésicas em doses muito menores que a tóxica.

Influence of lactation on motor activity and elevated plus maze behavior

Lactating rats show less noise-induced freezing and fewer inhibitory responses on the 6th day post-delivery when submitted to water and food deprivation in a classical conflict paradigm. Lactating mice go more often to the illuminated chamber in a light-dark cage and stay longer in it than virgin females. The present study was designed to assess the influence of this physiological state, i.e. lactation, on the elevated plus maze (EPM) and open-field behavior in adult female rats. Total (TL) and central (CL) locomotion and rearing (RF) frequencies were measured in an open-field. Number of entries into the open and closed arms as well as the time spent in each of these arms were measured in the EPM. Percent time spent and number of entries into the open arms were calculated and compared. In the open-field, TL was significantly decreased (115 + 10.6 vs 150 + 11.6) while CL and RF did not differ from those presented by virgin rats. In the EPM, lactating rats displayed a significant reduction in percent time spent (10.9 ñ 1.5 vs 17.4 ñ 2.3) in the open arms as well as a tendency to a reduction in percent entries into the open arms (35.7 ñ 4.7 vs 45.7 ñ 4.3). These results show that the physiological state of lactation modulates the open-field and EPM behaviors in rats.

Is perinatal picrotoxin anxiogenic?

Female Wistar rats were exposed to a subconvulsant dose of picrotoxin (0.75 mg/Kg,sc) on day 18 of pregnancy, immediately after paturition and daily during the first 5 days of lactation. In adulthood, the offspring were tested in an open-field, in an elevated plus maze and for social interaction. Results showed increased locomotor activity (75 days of age) and decreased social interaction (90 days of age) in experimental male rats compared to control male rats. No effects on behaviors related to anxiety were observed in males or females tested in the plus maze apparatus. An additional comparison of the activity male animals perinatally treated with picrotoxin showed a lack of the classical sexual dimorphic responses in the open-field (control male = 68.7 ñ 6.31; control female = 98.4 ñ 6.31; edxperimental male = 89.6 ñ 6.32; experimental female = 113.2 ñ 4.74). We suggest that perinatal picrotoxin exposure may interfere with normal male masculinization rather increasing anxiety in male rats

The diphenhydramine-induced decrease in general open-field activity of female rats is gonadal steroid dependent

The effect of ovarian steroids on sedative effects of diphenhydramine (D), a histamine H1 receptor blocker, was determined. Seventy-five female Wistar rats were randomly divided into three groups: Group 1 (N = 54) was ovariectomized, group 2 (N = 7) was sham-operated, and group 3 (N = 14) was intact. The ovariectomized rats were then subdivided into 4 groups. Two groups received peanut oil 54 and 6 h before treatment with saline solution (group OS) or 20 mg/kg D (group OD). The other two groups received 50 micrograms/kg 17-beta-estradiol and 2 mg/kg progesterone, respectively, 54 and 6h before treatment with saline solution (group OHS) or 20 mg/kg D (group OHD). The sham-operated animals were treated as the OS group. Intact animals were injected with saline (group IS) or 20 mg/kg D (group ID) on the day of estrus, as determined by vaginal smears taken in the morning before the behavioral observations. Rats were observed for 6 min in the open field during the dark period of the cycle, 15 min after the administration of saline or D. There was a similar decrease in locomotion and rearing frequencies in OHS vs OHD and IS vs ID groups. Nevertheless, a lack of D sedative effect was observed in OD rats (locomotion and rearing frequencies, 56.0 +/- 3.3 vs 46.1 +/- 3.8 and 15.5 +/- 1.6 vs 15.2 +/- 1.6., for OS and OD groups, respectively). The results suggest that the sedative effect of diphenhydramine depends on the presence of ovarian steroids

Behavioral and biochemical effects of Xylazine: possible interactions between central noradrenergic-dopaminergic systems

Alguns efeitos comportamentais e bioquímicos da xilazina foram estudados em ratos e camundongos. Os resultados mostraram que a xilazina: a)diminuiu a atividade geral de ratos e camundongos observados em campo-aberto; b) foi incapaz de produzir catatonia e suprimiu este comportamento induzido pelo haloperidol em camundongos; c) potencializou o comportamento estereotipado induzido pela apomorfina em ratos; d) aumentou os nívei cerebrais de noradrenalina, porém näo alterou aqueles de dopamina. Estes resultados foram discutidos considerando-se açäo da xilazina em sistemas noradrenérgicos centrais e da interaçäo entre sistemas noradrenérgicos e dopaminérgicos centrais

Effects of exposure to a pyrethroid insecticide during lactation on the behavior of infant and adult rats

Cyhalothrin, a pyrethroid insecticide, was administered to female Wistar rats as a 0.02% solution plus 0.04% sucrose (w/v) in drinking water from whelping to pup weaning after 21 days of lactation. The pesticide did not change the maternal behavior of the dams as measured by the scoring system of Sderstein and Eneroth. The body weight of pups exposed to the pesticide and at age 90 days was not different from that of controls, and the motor activity of the pups measured in a simple photocell activity cage was not affected by pesticide treatment. Furthermore, no overt sings of neural toxicity were observed in the offspring. However, the treatment disrupted rat behavior in adulthood when assessed by using an inhibitory avoidance learning task. Thus, inhibitory avoidance tests carried out on rats at 90 days of age were capable of demonstrating neural toxicity of Cyhalothrin (0.02%) present only in the drinking water of dams during 21 days of lactation

Effects of prenatal diphenhydramine administration on sexual behavior in rats

In order to study the involvement of the brain histamine system on the sexual vehavior of rats prenatally exposed to the histamine H1 receptor blockader, diphenhydramine (DPD), the famale lordotic response and male sexual behavior were aalyzed. The results show that the lorditic response in the prenatal DPD-treated rats was increased in relation to control animals. Impairment of male sexual behavior was indicated by an invrease in ejaculation latency, in the number of mounts and a decrease in the number of ejaculations up to 30 min after the first intromission. Prenatal expossure to DPD thus appears to alter female and male sexual behavior on reaching adulthood

Implicacoes fisiopatologicas do uso cronico de neurolepticos. / Physiopathological involvement of the chronical use of neuroleptics

Analisou-se as implicacoes fisiopatologicas do uso cronico de neurolepticos.O trabalho, inicialmente, discute as hipoteses explicativas da esquizofrenia paranoide, associando-a a um excesso de atividade dopaminergica central ou a quebra do balanco entre neurotransmissores. Por outro lado, os autores relacionam os efeitos antipsicoticos e os extrapiramidais dos neurolepticos com o desenvolvimento de fenomenos adaptativos do sistema nervoso central induzidos pelo tratamento cronico com as drogas. Neste particular relevam a existencia de bloqueios diferenciais produzidos pelos neurolepticos nos diferentes sistemas dopaminergicos centrais e comentam sua importancia