Conditional Deletion of Ric-8b in Olfactory Sensory Neurons Leads to Olfactory Impairment.

The olfactory system can discriminate a vast number of odorants. This ability derives from the existence of a large family of odorant receptors expressed in the cilia of the olfactory sensory neurons. Odorant receptors signal through the olfactory-specific G-protein subunit, Gαolf. Ric-8b, a guanine nucleotide exchange factor, interacts with Gαolf and can amplify odorant receptor signal transduction in vitro To explore the function of Ric-8b in vivo, we generated a tissue specific knock-out mouse by crossing OMP-Cre transgenic mice to Ric-8b floxed mice. We found that olfactory-specific Ric-8b knock-out mice of mixed sex do not express the Gαolf protein in the olfactory epithelium. We also found that in these mice, the mature olfactory sensory neuron layer is reduced, and that olfactory sensory neurons show increased rate of cell death compared with wild-type mice. Finally, behavioral tests showed that the olfactory-specific Ric-8b knock-out mice show an impaired sense of smell, even though their motivation and mobility behaviors remain normal.SIGNIFICANCE STATEMENT Ric-8b is a guanine nucleotide exchange factor (GEF) expressed in the olfactory epithelium and in the striatum. Ric-8b interacts with the olfactory Gαolf subunit, and can amplify odorant signaling through odorant receptors in vitro However, the functional significance of this GEF in the olfactory neurons in vivo remains unknown. We report that deletion of Ric-8b in olfactory sensory neurons prevents stable expression of Gαolf. In addition, we demonstrate that olfactory neurons lacking Ric-8b (and consequently Gαolf) are more susceptible to cell death. Ric-8b conditional knock-out mice display impaired olfactory guided behavior. Our results reveal that Ric-8b is essential for olfactory function, and suggest that it may also be essential for Gαolf-dependent functions in the brain.

Zinc Alleviates Lipopolysaccharide Interference with Both Body Temperature and Sickness Behavior in Virgin Female Rats.

OBJECTIVES: Previous studies from our group showed that lipopolysaccharide (LPS) exposure induces several signs of sickness behavior, including a decrease in food consumption, body weight gain, adipsia, and a biphasic effect in tympanic temperature with a first phase of hypothermia, followed by an increased tympanic temperature. LPS can activate a chain of nonspecific host responses, including the immune response, and decreased zinc levels. In addition, there are differences in the immune response between males and females, particularly fever, with sex hormones interfering with body temperature. This study aims to characterize the effects of zinc treatment on tympanic temperature, body weight gain, food and water consumption, and general activity in open field of virgin female rats exposed to a dose of LPS that was previously reported to induce sickness behavior. METHODS: Virgin female Wistar rats were treated with either saline (S) or LPS. One hour later, the S group received another injection of saline (S + S group), half of the LPS group received saline (LPS + S group) and the other half received zinc (LPS + Zn group). Tympanic temperature, body weight, and water and food consumption were measured for 96 h. Measurements and observations started 2 h after LPS administration. RESULTS: Treatment with zinc attenuated LPS-increased temperature, decreased the body weight gain and food consumption, and water consumption was increased. CONCLUSION: Zinc treatment is beneficial as it reduces the increased tympanic temperature induced by LPS, but it does not influence other sickness behavior caused by exposure to LPS.

Short-Term Hyperprolactinemia Reduces the Expression of Purinergic P2X7 Receptors during Allergic Inflammatory Response of the Lungs.

PURPOSE: We have previously shown that domperidone-induced short-term hyperprolactinemia reduces the lung's allergic inflammatory response in an ovalbumin antigenic challenge model. Since purinergic receptor P2X7R activity leads to proinflammatory cytokine release and is possibly related to the pathogenesis of allergic respiratory conditions, the present study was designed to investigate a possible involvement of purinergic and prolactin receptors in this phenomenon. METHODS: To induce hyperprolactinemia, domperidone was injected intraperitoneally in rats at a dose of 5.1 mg × kg-1 per day for 5 days. P2X7 expression was evaluated by lung immunohistochemistry while prolactin receptor expression in bronchoalveolar lavage leukocytes was analyzed through flow cytometry. RESULTS: Previous reports demonstrated that rats subjected to short-term hyperprolactinemia exhibited a decrease in leukocyte counts in bronchoalveolar lavage, especially granulocytes. Here, it is revealed that hyperprolactinemia promotes an increased expression of prolactin receptors in granulocytes. Also, increased expression of purinergic P2X7R observed in allergic animals was significantly reduced by hyperprolactinemia. CONCLUSIONS: Both purinergic and prolactin receptor expression changes occur during the anti-asthmatic effect of hyperprolactinemia.

Lipopolysaccharide-induced sickness behavior in lactating rats decreases ultrasonic vocalizations and exacerbates immune system activity in male offspring.

OBJECTIVE: The present study analyzed the effects of lipopolysaccharide (LPS) on maternal behavior during lactation and possible correlations with changes in emotional and immune responses in offspring. METHODS: Lactating rats received 100 µg/kg LPS, and the control group received saline solution on lactation day (LD) 3. Maternal general activity and maternal behavior were observed on LD5 (i.e. the day that the peak of fever occurred). In male pups, hematological parameters and ultrasonic vocalizations (USVs) were assessed on LD5. At weaning, an additional dose of LPS (50 µg/kg, i.p.) was administered in male pups, and open-field behavior, oxidative burst and phagocytosis were evaluated. RESULTS: A reduction in the time in which dams retrieved the pups was observed, whereas no effects on maternal aggressive behavior were found. On LD5, a reduction of the frequency of USVs was observed in pups, but no signs of inflammation were found. At weaning, an increase in immune system activity was observed, but no differences in open-field behavior were found. CONCLUSION: These results indicate that inflammation in lactating mothers disrupted mother/pup interactions and may have produced short- and long-term effects on pup behavior as well as biological pathways that modulate inflammatory responses to bacterial endotoxin challenge in pups.

The mother as hunter: significant reduction in foraging costs through enhancements of predation in maternal rats.

In previous laboratory investigations, we have identified enhanced cognition and reduced stress in parous rats, which are likely adaptations in mothers needing to efficiently exploit resources to maintain, protect and provision their immature offspring. Here, in a series of seven behavioral tests on rats, we examined a natural interface between cognition and resource gathering: predation. Experiment 1 compared predatory behavior (toward crickets) in age-matched nulliparous mothers (NULLs) and postpartum lactating mothers (LACTs), revealing a highly significant enhancement of predation in LACT females (mean = -65s in LACTs, vs. -270s in NULLs). Experiment 2 examined the possibility that LACTs, given their increased metabolic rate, were hungrier, and thus more motivated to hunt; doubling the length of time of food deprivation in NULLs did not decrease their predatory latencies. Experiments 3-5, which examined sensory regulation of the effect, indicated that olfaction (anosmia), audition (blockade with white noise), and somatosensation (trimming the vibrissae) appear to play little role in the behavioral enhancement observed in the LACTs; Experiment 6 examined the possibility that visual augmentations may facilitate the improvements in predation; testing LACTs in a 0-lux environment eliminated the behavioral advantage (increasing their latencies from -65s to -212s), which suggests that temporary augmentation to the visual system may be important, and with hormone-neural alterations therein a likely candidate for further study. In contrast, testing NULLS in the 0-lux environment had the opposite effect, reducing their latency to catch the cricket (from -270s to -200s). Finally, Experiment 7 examined the development of predatory behavior in Early-pregnant (PREG), Mid-PREG, and Late-PREG females. Here, we observed a significant enhancement of predation in Mid-PREG and Late-PREG females--at a time when maternity-associated bodily changes would be expected to diminish predation ability--relative to NULLs. Therefore, as with the increasing reports of enhancements to the maternal brain, it is apparent that meaningful behavioral adaptations occur that likewise promote the survival of the mother and her infants at a crucial stage of their lives.

Maternal treatment with picrotoxin in late pregnancy improved female sexual behavior but did not alter male sexual behavior of offspring.

Previous studies from our laboratory investigated the effects of picrotoxin (PT), a γ-aminobutyric acid receptor antagonist administered during several perinatal periods, on the sexual behavior of male and female rats. We observed that the time of perinatal exposure to PT is critical to determine either facilitation or impairment of sexual behavior. The present study evaluated the effects of prenatal administration of a single dose of PT on gestation day 18 of dams (the first critical period of male brain sexual differentiation) on sexual behavior of male and female offspring. Thus, female Wistar rats were mated with males and, on gestation day 18, received 0.6 mg/kg of PT or 0.9% saline solution subcutaneously. On postnatal day 1, the offspring were weighed and several measures of sexual development were assessed. The sexual behaviors and the general activity in the open field of adult male and ovariectomized, hormone-treated female rats were observed. On comparison with the control group, maternal PT treatment: (i) did not alter the maternal weight, pup weight, anogenital distance, or male and female general activity; (ii) increased female sexual behavior, that is, decreased the latencies to first mount, first lordosis, and tenth lordosis, and the percentage of females presenting lordosis; and (iii) did not alter male sexual behavior. It is suggested that prenatal PT exposure interfered with epigenetic mechanisms related to the development of sex differences in the brain, leading to the observed sexually dimorphic effects on sexual behavior.

Maternal exposure to picrotoxin modifies the response of the GABAA receptor during sexual behavior of adult male rat offspring.

This study investigated whether perinatal exposure to picrotoxin, a GABAA antagonist, modifies the effect of muscimol, a GABAA agonist, on the sexual behavior of adult male rats. Two hours after birth and then once daily during the next 9 days of lactation, dams received picrotoxin (0.75 mg/kg subcutaneously) or saline (1 ml/kg subcutaneously). The adult male offspring from the picrotoxin and saline groups received saline (1 ml/kg intraperitoneally) or muscimol (1 mg/kg intraperitoneally), and 15 min later, their sexual behavior was assessed. Muscimol treatment in the saline-exposed group increased the mount and intromission latencies. However, these effects were absent in the picrotoxin-exposed groups. The latencies to first ejaculation, postejaculatory mount, and intromission were decreased in both picrotoxin-exposed groups relative to the saline-exposed groups. The picrotoxin+muscimol-treated rats required more intromissions to ejaculate and the picrotoxin-exposed groups made more ejaculations than the saline-exposed groups. Thus, muscimol treatment did not increase the mount and intromission latencies following picrotoxin exposure, but increased the ejaculation frequency, which did not differ between the picrotoxin+muscimol and the picrotoxin+saline groups. These data indicate that perinatal picrotoxin treatment interfered with GABAA receptor development.

Dual effects of hyperprolactinemia on carrageenan-induced inflammatory paw edema in rats.

OBJECTIVES: The effects of short-term 5-day and long-term 30-day hyperprolactinemia induced by domperidone (1.7 mg/kg/day, s.c.) or ectopic pituitary graft on the acute inflammatory response induced by carrageenan were evaluated in male rats. Both models of hyperprolactinemia effectively increased serum prolactin (PRL) levels. METHODS: The volume in milliliters of inflammatory edema was measured by plethysmography 1, 2, 3, 4, 6, 8 and 24 h after carrageenan injection. The areas under the inflammatory time-response curves were compared. Additionally, the effects of hyperprolactinemia on body weight and serum corticosterone levels were evaluated. RESULTS: In both domperidone-treated and pituitary graft-implanted animals, short-term 5-day hyperprolactinemia increased the inflammatory response, while long-term 30-day hyperprolactinemia had anti-inflammatory effects. Body weight was not affected by either short- or long-term hyperprolactinemia. CONCLUSION: These results show that PRL has biphasic effects on the carrageenan-induced inflammatory response.

Pioglitazone abolishes cognition impairments as well as BDNF and neurotensin disturbances in a rat model of autism.

We have shown that exposure of rats to lipopolysaccharide (LPS) during gestation induces autistic-like behaviors in juvenile offspring and pioglitazone post treatment corrects social and communication deficits. The first objective of the present study was to evaluate the cognition of the rats, because this is also a behavioral sphere committed in autism. Second, biomarkers related to pioglitazone pathways and autism were studied to try to understand their mechanisms. We used our rat model of autism and pioglitazone was administered daily to these young offspring. T-maze spontaneous alternations tests, plasma levels of brain-derived neurotrophic factor (BDNF), beta-endorphin, neurotensin, oxytocin, and substance P were all studied. Exposure of rats to LPS during gestation induced cognitive deficits in the young offspring, elevated BDNF levels and decreased neurotensin levels. Daily postnatal pioglitazone treatment abolished cognition impairments as well as BDNF and neurotensin disturbances. Together with our previous studies, we suggest pioglitazone as a candidate for the treatment of autism, because it improved the responses of the three most typical autistic-like behaviors. BDNF and neurotensin also appeared to be related to the autistic-like behaviors and should be considered for therapeutic purposes.

In vitro macrophage activity: biphasic effect of prolactin and indirect evidence of dopaminergic modulation.

OBJECTIVE: Prolactin (PRL), a peptide hormone produced by the pituitary gland, is involved in the interaction between the neuroendocrine and immune system. Since dopamine receptor antagonists increase serum levels of PRL, both PRL and dopamine receptors might be involved in the modulation of macrophage activity, providing means of communication between the nervous and immune systems. This study evaluated the effects of PRL and the dopamine antagonist domperidone (DOMP) on macrophage activity of female rats. METHODS: Oxidative burst and phagocytosis of peritoneal macrophages were evaluated by flow cytometry. Samples of peritoneal liquid from female rats were first incubated with PRL (10 and 100 nM) for different periods. The same procedure was repeated to evaluate the effects of DOMP (10 and 100 nM). RESULTS: In vitro incubation of macrophages with 10 nM DOMP decreased oxidative burst, after 30 min, whereas the PMA-induced burst was decreased by DOMP 10 nM after 2 and 4 h. Treatment with PRL (10 and 100 nM) for 30 min decreased oxidative burst and rate of phagocytosis (10 nM). After 2 h of incubation, 10 nM PRL decreased oxidative burst and phagocytosis intensity, but increased the rate of phagocytosis. On the other hand, after 4 h, PRL 10 and 100 nM increased oxidative burst and the rate of phagocytosis, but decreased intensity of phagocytosis. CONCLUSIONS: These observations suggest that macrophage functions are regulated by an endogenous dopaminergic tone. Our data also suggest that both PRL and dopamine exert their action by acting directly on the peritoneal macrophage.

Behavioral effects of acute stimulation of kappa-opioid receptors during lactation.

The behavioral effects of the kappa-opioid receptor agonist U69593 were examined in lactating rats. On day 5 of lactation, animals were treated with 0.1 mg/kg of U69593 to determine whether it influences general activity and maternal latencies toward pups. Because little attention has been given to the possibility that pre-mating treatment with morphine may modulate the response to kappa-opioid receptor stimulation, another group of animals was submitted to the same acute challenge after abrupt withdrawal from repeated treatment with morphine sulfate during the pre-mating period (5 mg/kg on alternate days for a total of five doses). Acute kappa-opioid stimulation reduced total locomotion, rearing frequency, and time spent self-grooming and increased immobility duration. These kappa agonist effects were not observed in animals pretreated with morphine. Similarly, latencies to retrieve pups were longer only in animals pretreated with saline and challenged acutely with U69593. None of these effects were observed in morphine sulfate-pretreated animals. The present results suggest that pre-mating repeated exposure to morphine produces a tolerance-like effect on behavioral responses to low-dose kappa-opioid receptor stimulation in active reproductive females.

Pioglitazone abolishes autistic-like behaviors via the IL-6 pathway.

Autism is characterized by social deficits, communication abnormalities, and repetitive behaviors. The risk factors appear to include genetic and environmental conditions, such as prenatal infections and maternal dietary factors. Previous investigations by our group have demonstrated that prenatal exposure to lipopolysaccharide (LPS), which mimics infections by gram-negative bacteria, induces autistic-like behaviors. No effective treatment yet exists for autism. Therefore, we used our rat model to test a possible treatment for autism. We selected pioglitazone to block or ease the impairments induced by LPS because although this drug was designed as an anti-diabetic drug (it has an insulin effect), it also exerts anti-inflammatory effects. Juvenile offspring were treated daily with pioglitazone, and the main behaviors related to autism, namely, socialization (play behavior) and communication (50-kHz ultrasonic vocalizations), were studied. Biomarkers linked to autism and/or pioglitazone were also studied to attempt to understand the mechanisms involved, namely, IL-6, TNF-alpha, MCP-1, insulin, and leptin. Prenatal LPS exposure induced social deficits and communicational abnormalities in juvenile rat offspring as well as elevated plasma IL-6 levels. Daily postnatal pioglitazone treatment blocked the impairments found in terms of the time spent on social interaction, the number of vocalizations (i.e., autistic-like behaviors) and the elevated plasma IL-6 levels. Thus, pioglitazone appears to be a relevant candidate for the treatment of autism. The present findings may contribute to a better understanding and treatment of autism and associated diseases.

Buried Food-seeking Test for the Assessment of Olfactory Detection in Mice.

The sense of smell allows animals to discriminate a large number of volatile environmental chemicals. Such chemical signaling modulates the behavior of several species that depend on odorant compounds to locate food, recognize territory, predators, and toxic compounds. Olfaction also plays a role in mate choice, mother-infant recognition, and social interaction among members of a group. A key assay to assess the ability to smell odorants is the buried food-seeking test, which checks whether the food-deprived mice can find the food pellet hidden beneath the bedding in the animal's cage. The main parameter observed in this test is the latency to uncover a small piece of chow, cookie, or other pleasant food, hidden beneath a layer of cage bedding, within a limited amount of time. It is understood that food-restricted mice which fail to use odor cues to locate food within a given time period are likely to have deficits in olfactory abilities. Investigators who used the buried food test, or versions of the buried food test, demonstrated that it is possible to evaluate olfactory deficits in different models of murine studies (Alberts and Galef, 1971; Belluscio et al., 1998 ; Luo et al., 2002 ; Li et al., 2013 ). We have recently used this assay to demonstrate that olfactory-specific Ric-8B knock-out mice (a guanine nucleotide exchange factor that interacts with olfactory-specific G-protein) show an impaired sense of smell ( Machado et al., 2017 ). Here we describe the protocol of the buried food-seeking test, as adopted in our assays.

The weaning period promotes alterations in the orexin neuronal population of rats in a suckling-dependent manner.

The orexin-immunoreactive neurons are part of an important arousal-promoting hypothalamic population. Several groups have investigated these neurons during the lactation period, when numerous physiological alterations occur in the dam's body to cope with the newly acquired metabolic needs of the litter. Although those studies have probed this population during the early and intermediate stages of lactation, few works have examined its response to weaning, including the cessation of the tactile suckling stimulus as the litter stops nursing. Using double immunohistochemistry for orexin and FOS combined with three-dimensional reconstruction techniques, we investigated orexin-synthesizing neurons and their activation at different times during weaning, in addition to the role played by the suckling stimulus. We report here that weaning promoted a decline in the anterior population of orexin-immunoreactive neurons and decreased the number of double orexin-FOS neurons labeled in the central dorsomedial hypothalamus, in addition to reducing the overall number of FOS-immunoreactive cells in the whole tuberal hypothalamus. Disruption of the suckling stimulus from the pups impaired the decrease in the number of anteriorly located orexin-immunoreactive neurons, attenuated the activation of orexin-synthesizing cells in the dorsomedial hypothalamus and reduced the number of FOS-immunoreactive neurons across the tuberal hypothalamus. When taken together, our data suggest that the weaning period is necessary to restore neurochemical pathways altered during the lactation period and that the suckling stimulus plays a significant role in this process.

Periaqueductal gray cholecystokinin infusions block morphine-induced disruption of maternal behavior.

Cholecystokinin (CCK) and opiates interaction is critical for maintaining maternal behavior during lactation. Morphine inhibits while CCK restores maternal behavior. Recently we have shown that periaqueductal gray (PAG) is a region critically involved in the opioidergic blockade of maternal behavior. A critical level of morphine-induced activation of the rostral lateral PAG is required to inhibit maternal behavior in lactating rats. Since central CCK injections reverted morphine-induced inhibition of maternal behavior, we tested whether this peptide would act similarly in the PAG. This hypothesis was confirmed in experiments showing that morphine's inhibitory effect on maternal responsiveness was blocked by 1.0 and 0.2 nmol CCK injections into the rostral PAG, but not in nearby regions of the mesencephalic reticular nucleus. To test for possible compensatory changes the CCK2 receptor due to morphine treatments the expression of CCK2 receptor mRNA was evaluated in the PAG. PAG CCK2 receptor cDNA amplification revealed no difference in morphine treated animals. These results broaden understanding of the role played by CCK in the PAG. This CCK action might not depend on changes in its receptor.

Blockade of neurotensin receptors during amphetamine discontinuation indicates individual variability.

Psychostimulant-induced locomotor sensitization has been related to changes within the mesolimbic dopamine system and has been suggested to be useful to study mechanisms underlying drug craving. Neurotensin is a neuropeptide co-localized with dopamine in the mesolimbic system. The response to novelty has been suggested to be a predictor of enhanced vulnerability to behavioral sensitization. The effects of repeated treatment with the neurotensin antagonist SR48692 after amphetamine discontinuation were investigated in mice previously classified as high responders (HRs) or low responders (LRs) to novelty. Mice were repeatedly treated with 2.0mg/kg amphetamine, every other day for 11 days. During the first 7 days after amphetamine discontinuation, the animals received a daily injection of saline or 0.3mg/kg SR48692. On the eighth day after amphetamine discontinuation all subjects received a 2.0mg/kg amphetamine challenge injection. Then, mice were tested for an open field behavior and after 90min, were sacrificed for Fos expression quantification in the nucleus accumbens. Both HRs and LRs expressed amphetamine-induced sensitized locomotor activation and increased expression of Fos protein. Treatment with SR48692 prevented behavioral sensitization and Fos protein expression enhancement in LRs but not in HRs mice. These data suggest that neurotensin plays a role in individual variability to amphetamine-induced sensitization.

Opiate regulation of behavioral selection during lactation.

Treatment of postpartum female rats with morphine inhibits maternal behavior. The same type of treatment stimulates foraging in adult animals. The aim of the present study was to investigate, in lactating rats, the functional role of opioid systems in the choice between caring for pups versus hunting insects. Experiment 1 was designed to test how acute morphine treatment with 3.0 mg/kg interferes with choosing between caring for pups versus predatory behavior. Morphine-treated dams decreased maternal behavior while increasing efficiency in hunting insects. The next step was to test the opioid antagonist naloxone in the same context of maternal versus predatory behavior. Naloxone restored maternal care and reduced hunting in morphine-treated rats. Finally, in order to test the role of endogenous opioidergic stimulation in this scenario, lactating rats were treated with the opioid antagonist naloxone alone. Consistently, naloxone treatment induced a decrease in number of insects captured and an increase in the percentage of animals displaying nursing behavior. These results provide important insight into the role of opioidergic transmission in the regulation of behavioral selection during lactation. The present results suggest that endogenous opioids may stimulate hunting by replacing maternal behavior during lactation.

A comparative study of morphine treatment regimen prior to mating and during late pregnancy.

Pre-mating treatment of female rats with morphine may have long-term effects. In this study, we analyzed the effects of two types of morphine sulfate pre-treatment: during pre-mating (5.0 mg/kg on alternate days for a total of seven doses) and during pregnancy (3.5 mg/(kgday) for 5 days starting on day 17 of pregnancy during early lactation. In order to evaluate possible morphine-induced behavioral changes, dams were tested for maternal behavior and locomotor activity during early lactation, and striatal and hypothalamic concentrations of dopamine and their metabolites and serum levels of corticosterone were measured. Maternal behavior was disrupted only in animals treated with morphine sulfate during pregnancy and challenged acutely (1.5 mg/kg) during lactation. Pre-mating treatment with morphine sulfate-induced changes in responses with increased locomotor activity, striatal dopamine turnover and serum corticosterone levels. None of these parameters were affected by morphine sulfate pre-treatment during late pregnancy. These data suggest that morphine has specific long-term and sometimes addictive-like effects on actively reproductive female animals that vary with the pre-treatment period, late pregnancy being particularly sensitive for effects on maternal behavior.

Rapidly induced dopaminergic supersensitivity: D1/D2 receptor participation and its prevention by an MAO-inhibitor.

The dopaminergic system requires combined dopamine D1/D2 receptor stimulation to express its activity; a phenomenon called synergism D1/D2. Dopamine receptors develop supersensitivity following dopamine de-afferentation and/or reserpine treatment. Acute supersensitivity occurs with reserpine treatment. The breakdown of D1/D2 synergism has been proposed implicating the genesis of this kind of supersensitivity. We sought to determine the best conditions for inducing acute dopaminergic supersensitivity evaluated by apomorphine-induced stereotyped behaviour, to examine whether D1/D2 synergism breakdown occurs in this reserpine-induced acute supersensitivity model, and whether it can be prevented by the monoamino-oxidase (MAO) inhibitor selegiline. Reserpine (2.0 mg/kg) was injected 3 h before apomorphine (0.6 mg/kg) induced stereotypy. D1/D2 synergism was investigated using specific antagonists (D1-SKF 83566 2.5 mg/kg, D2-haloperidol 2.0 mg/kg) and selegiline (10 mg/kg) was used to analyze the influence of dopamine "de-novo" synthesis. All antagonist treatments suppressed stereotypy and selegiline prevented supersensitivity. These data suggest that reserpine-induced acute dopaminergic supersensitivity is not due to the breakdown of D1/D2 synergism and such supersensitivity can be prevented by recently synthesised dopamine.

Attenuated allergic inflammatory response in the lungs during lactation.

AIMS: To evaluate the influence of lactation on lung immune function during allergic inflammation. MAIN METHODS: Female rats, 60-90days old, were divided into three groups: no lung allergy virgins (N group), ovalbumin (OVA)-immunized and sensitized virgins (V group), and OVA-immunized and sensitized lactating females (L group). On gestation day (GD) 10, all animals in L group received a subcutaneous injection of 0.1mg·kg(-1) OVA plus aluminum hydroxide. On GD17, the L group received a subcutaneous booster injection of 10µg OVA plus 10mg aluminum hydroxide. After 7days, an inhalatory challenge with 1% OVA was given in 15min sessions for 3 consecutive days. Animals from the V group received the same treatment, meaning both tests and time intervals between OVA treatment and inhalatory challenge were the same as in the L group. Twenty-four hours after the last inhalation session, the animals were euthanized, and the following tests were performed: total and differential bronchoalveolar lavage (BAL) and femoral marrow lavage (FML) leukocyte counts, quantification of tumor necrosis factor α (TNF-α) and interferon γ (IFN-γ) levels in BAL fluid, and quantification of plasma corticosterone and catecholamine levels. KEY FINDINGS: The L group presented lower BAL total leukocyte counts and decreases in the number of eosinophils and macrophages compared with the V group. They also expressed higher BAL IFN-γ and lower plasma corticosterone levels. Plasma norepinephrine levels were higher in the L group than in the N and V groups. SIGNIFICANCE: Lactating female rats presented less intense allergic lung inflammation. Our findings suggest that lactation may protect females from asthmatic crises.