Astrocytic Hydrogen Sulfide Regulates Supraoptic Cellular Activity in the Adaptive Response of Lactating Rats to Chronic Social Stress

Maternal social stress among breastfeeding women can be adapted in chronic process. However, neuroendocrine mechanisms underlying such adaptation remain to be identified. Here, we report the effects of 2 hr/day unfamiliar male rat invasion (UMI) stress on maternal behaviors in lactating rats during postpartum day 8 (UMI8) to postpartum day 12 (UMI12). Rat dams at UMI8 presented signs of maternal anxiety, depression, and attacks toward male intruder. These changes partially reversed at UMI12 except the sign of anxiety. In the supraoptic nucleus (SON), UMI12 but not UMI8 significantly increased the expression of c-Fos and phosphorylated extracellular signal-regulated protein kinase 1/2. At UMI8 but not UMI12, length of glial fibrillary acidic protein (GFAP, astrocytic cytoskeletal element) filaments around oxytocin (OT) neurons was significantly longer than that of their controls; the amount of GFAP fragments at UMI12 was significantly less than that at UMI8. Expression of cystathionine β-synthase (CBS, enzyme for H2S synthesis) at UMI12 was significantly higher than that at UMI8. CBS expression did not change significantly in the somatic zone of the SON but decreased significantly at the ventral glia lamina at UMI8. In brain slices of the SON, aminooxyacetate (a CBS blocker) significantly increased the expression of GFAP proteins that were molecularly associated with CBS. Aminooxyacetate also reduced the firing rate of OT neurons whereas Na2S, a donor of H2S, increased it. The adaptation during chronic social stress is possibly attributable to the increased production of H2S by astrocytes and the subsequent retraction of astrocytic processes around OT neurons.

Need-based prioritization of behavior

When presented with a choice, organisms need to assimilate internal information with external stimuli and past experiences to rapidly and flexibly optimize decisions on a moment-to-moment basis. We hypothesized that increasing hunger intensity would curb expression of social behaviors such as mating or territorial aggression; we further hypothesized social interactions, reciprocally, would influence food consumption. We assessed competition between these motivations from both perspectives of mice within a resident-intruder paradigm. We found that as hunger state escalated, resident animal social interactions with either a female or male intruder decreased. Furthermore, intense hunger states, especially those evoked via AgRP photoactivation, fundamentally altered sequences of behavioral choice; effects dependent on food availibility. Additionally, female, but not male, intrusion attenuated resident mouse feeding. Lastly, we noted environmental context-dependent gating of food intake in intruding mice, suggesting a dynamic influence of context cues on the expression of feeding behaviors.

Ethanol during adolescence decreased the BDNF levels in the hippocampus in adult male Wistar rats, but did not alter aggressive and anxiety-like behaviors

Objective:To investigate the effects of ethanol exposure in adolescent rats during adulthood by assesssing aggression and anxiety-like behaviors and measuring the levels of inflammatory markers.Methods:Groups of male Wistar rats (mean weight 81.4 g, n = 36) were housed in groups of four until postnatal day (PND) 60. From PNDs 30 to 46, rats received one of three treatments: 3 g/kg of ethanol (15% w/v, orally, n = 16), 1.5 g/kg of ethanol (12.5% w/v, PO, n = 12), or water (n = 12) every 48 hours. Animals were assessed for aggressive behavior (resident x intruder test) and anxiety-like behaviors (elevated plus maze) during adulthood.Results:Animals that received low doses of alcohol showed reduced levels of brain-derived neurotrophic factor (BDNF) in the hippocampus as compared to the control group. No significant difference was found in prefrontal cortex.Conclusions:Intermittent exposure to alcohol during adolescence is associated with lower levels of BDNF in the hippocampus, probably due the episodic administration of alcohol, but alcohol use did not alter the level agression toward a male intruder or anxiety-like behaviors during the adult phase.

Social stress induces glucocorticoid resistance in macrophages

Stress-induced levels of plasma glucocorticoid hormones are known to modulate leukocyte function. These experiments examined the effects of a social stressor on the responsiveness of peripheral immune cells. Male mice experienced six evening cycles of social disruption (SDR), in which an aggressive male intruder was placed into their home cage for 2 h. Although circulating corticosterone was elevated in SDR mice, they had enlarged spleens and increased numbers of splenic leukocytes. Splenocytes from SDR and control mice were cultured with lipopolysaccharide and corticosterone. Cells from SDR mice exhibited decreased sensitivity to the antiproliferative effects of corticosterone, suggesting that the peripheral immune cells were resistant to glucocorticoids. In addition, SDR cells produced more interleukin (IL)-6. To determine which cell population was affected, we used antibody-labeled magnetic beads to deplete splenocyte suspensions of B cells or macrophages. Depletion of macrophages from SDR cultures, but not depletion of B cells, abolished both the corticosterone resistance and enhanced IL-6 secretion. These findings demonstrate that a psychosocial stressor induced glucocorticoid resistance in mouse splenic macrophages.

Influences of Motivation On Display Divergences in Three Cichlid Fish Species (Haplochromis)

Differences between three cichlid fish species in responsiveness to a restrained territorial intruder have been investigated while an experimenter, considered a disturbing stimulus, was sitting 2 meters in front of the tank in view of the fish. The purpose of the analyses was to determine which motivational factors control responses to intruders and disturbances between Haplochromis elegans, H. squamipinnis, and H. angustifrons. This could be done on the basis of a model for the causal organization of these responses that was developed in an earlier paper (CARLSTEAD, 1982). It was found that H. angustifrons responds significantly less to the intruder than the other two species, and this is because it responds more to the experimenter. H. squampinnis hides from the experimenter in longer bouts than the other two. It was concluded that angustifrons has a basically higher activation level of system D (refer to model, Fig. 3), a system determining the responsiveness to stimuli indicative of potential danger and controlling motor patterns for hiding responses. Elegans has a relatively higher activation level of system T for responding to territorial intruders. Squamipinnis was found to have a higher level of a general factor for reactivity to all unexpected, thus novel stimuli. Species differences in courtship display were also investigated. These displays differ little between species, but each shows one particular display more often than expected in temporal association with spawning. This display proved in each species to be the display performed more often than expected to a restrained male territorial intruder in the behavior sequence after a conflict to approach it or withdraw from it had occurred (Turning-Around). Using the model, the motivational differences between the three species described above could account for the latter differences. If only one particular motivational configuration can be assumed to be required for a display to occur in any situation, then a approach/withdrawal conflict to a male intruder and a female showing willingness to spawn must elicit the same motivational configuration. It was concluded that species divergences in the activation level of certain motivational factors are reflected in this particular momentary motivational configuration. Characteristics of each species' ecological niche in Lake George, to which they are all endemic, have been discussed with respect to the factors selecting for these motivational divergences, It was concluded that the hypothesis is supported that adaptations for features of a species' habitat may cause divergences in display behavior that are not directly selected for their signal value. This occurs through selection for optimal activation levels of motivational factors that in the behavioral organization control both responsiveness to types of environmental stimuli and motor patterns of display.

A Comparison of Effects of Simple Experimental Manipulations On Fighting Generated By Breeding Activity and Predatory Aggression in 'To' Strain Mice

A preliminary study was conducted to examine the influences of simple experimental manipulations on aggressiveness generated by breeding activity and locust-killing behaviour (a form of predatory aggression?) in 'TO' strain mice. In females, where response to a male intruder was the form of intraspecific aggression investigated, factors examined included: a) female's reproductive status (namely pregnant or lactating) ; b) time since parturition; c) gonadal steroid production; d) anosmia. In males, rank-related fighting and locust killing were contrasted in animals from the breeding situation, from individual housed mice and from unisexual groups of experimental animals. A comparison of these intra- and inter-specific forms of aggression confirm that they can be influenced in very different ways by situational and physiological variables. Both maternal aggression and rank-related fighting were suppressed by anosmia. The results reiterate the need to specify which form of 'aggression' is being used in a particular study.