Female novelty and the courtship behavior of male guinea pigs (Cavia porcellus)

In several rodent species, an increase or recovery of sexual behavior can be observed when sexually satiated males are placed in contact with a novel mate. In order to assess the influence of female novelty on the courtship behavior of guinea pigs (Cavia porcellus), four adult males were observed during four daily 15-min sessions while interacting with the same pregnant female (same-female sessions). A new female was presented during the fifth session (switched-female session). The duration of behavioral categories was obtained from videotape records using an observational software. From the first to the second session, all males decreased the time allocated to investigating (sniffing and licking), following, and mounting the female, and that response did not recover by the end of the same-female sessions. No similar decreasing tendencies were detected in the circling or rumba categories. A marked increase of investigating occurred in all males from the last same-female session (8.1, 11.9, 15.1 and 17.3 percent session time) to the switched-female one (16.4, 18.4, 37.1 and 28.9 percent session time, respectively). Increases in following and circling were recorded in three of four males, and full-blown recovery of mounting in one male. No consistent changes in the females' responses to males (following or attacking) were observed throughout testing. These results are consistent with the hypothesis that guinea pig males recognize individual females and that courtship responses may suffer a habituation/recovery process controlled by mate novelty.

The terrestrial Gastropoda Megalobulimus abbreviatus as a useful model for nociceptive experiments: effects of morphine and naloxone on thermal avoidance behavior

We describe the behavior of the snail Megalobulimus abbreviatus upon receiving thermal stimuli and the effects of pretreatment with morphine and naloxone on behavior after a thermal stimulus, in order to establish a useful model for nociceptive experiments. Snails submitted to non-functional (22ºC) and non-thermal hot-plate stress (30ºC) only displayed exploratory behavior. However, the animals submitted to a thermal stimulus (50ºC) displayed biphasic avoidance behavior. Latency was measured from the time the animal was placed on the hot plate to the time when the animal lifted the head-foot complex 1 cm from the substrate, indicating aversive thermal behavior. Other animals were pretreated with morphine (5, 10, 20 mg/kg) or naloxone (2.5, 5.0, 7.5 mg/kg) 15 min prior to receiving a thermal stimulus (50ºC; N = 9 in each group). The results (means ± SD) showed an extremely significant difference in response latency between the group treated with 20 mg/kg morphine (63.18 ± 14.47 s) and the other experimental groups (P < 0.001). With 2.5 mg/kg (16.26 ± 3.19 s), 5.0 mg/kg (11.53 ± 1.64 s) and 7.5 mg/kg naloxone (7.38 ± 1.6 s), there was a significant, not dose-dependent decrease in latency compared to the control (33.44 ± 8.53 s) and saline groups (29.1 ± 9.91 s). No statistically significant difference was found between the naloxone-treated groups. With naloxone plus morphine, there was a significant decrease in latency when compared to all other groups (minimum 64% in the saline group and maximum 83.2% decrease in the morphine group). These results provide evidence of the involvement of endogenous opioid peptides in the control of thermal withdrawal behavior in this snail, and reveal a stereotyped and reproducible avoidance behavior for this snail species, which could be studied in other pharmacological and neurophysiological studies.

Apoptotic mimicry: an altruistic behavior in host/Leishmania interplay

Apoptosis is the most common phenotype observed when cells die through programmed cell death. The morphologic and biochemical changes that characterize apoptotic cells depend on the activation of a diverse set of genes. Apoptosis is essential for multicellular organisms since their development and homeostasis are dependent on extensive cell renewal. In fact, there is strong evidence for the correlation between the emergence of multicellular organisms and apoptosis during evolution. On the other hand, no obvious advantages can be envisaged for unicellular organisms to carry the complex machinery required for programmed cell death. However, accumulating evidence shows that free-living and parasitic protozoa as well as yeasts display apoptotic markers. This phenomenon has been related to altruistic behavior, when a subpopulation of protozoa or yeasts dies by apoptosis, with clear benefits for the entire population. Recently, phosphatidylserine (PS) exposure and its recognition by a specific receptor (PSR) were implicated in the infectivity of amastigote forms of Leishmania, an obligatory vertebrate intramacrophagic parasite, showing for the first time that unicellular organisms use apoptotic features for the establishment and/or maintenance of infection. Here we focus on PS exposure in the outer leaflet of the plasma membrane - an early hallmark of apoptosis - and how it modulates the inflammatory activity of phagocytic cells. We also discuss the possible mechanisms by which PS exposure can define Leishmania survival inside host cells and the evolutionary implications of apoptosis at the unicellular level.

An empirical comparison of atypical bulimia nervosa and binge eating disorder

The International Classification of Diseases, 10th edition (ICD-10) defines atypical bulimia nervosa (ABN) as an eating disorder that encompasses several different syndromes, including the DSM-IV binge eating disorder (BED). We investigated whether patients with BED can be differentiated clinically from patients with ABN who do not meet criteria for BED. Fifty-three obese patients were examined using the Structured Clinical Interview for DSM-IV and the ICD-10 criteria for eating disorders. All volunteers completed the Binge Eating Scale (BES), the Beck Depression Inventory, and the Symptom Checklist-90 (SCL-90). Individuals fulfilling criteria for both ABN and BED (N = 18), ABN without BED (N = 16), and obese controls (N = 19) were compared and contrasted. Patients with ABN and BED and patients with ABN without BED displayed similar levels of binge eating severity according to the BES (31.05 ± 7.7 and 30.05 ± 5.5, respectively), which were significantly higher than those found in the obese controls (18.32 ± 8.7; P < 0.001 and P < 0.001, respectively). When compared to patients with ABN and BED, patients with ABN without BED showed increased lifetime rates of agoraphobia (P = 0.02) and increased scores in the somatization (1.97 ± 0.85 vs 1.02 ± 0.68; P = 0.001), obsessive-compulsive (2.10 ± 1.03 vs 1.22 ± 0.88; P = 0.01), anxiety (1.70 ± 0.82 vs 1.02 ± 0.72; P = 0.02), anger (1.41 ± 1.03 vs 0.59 ± 0.54; P = 0.005) and psychoticism (1.49 ± 0.93 vs 0.75 ± 0.55; P = 0.01) dimensions of the SCL-90. The BED construct may represent a subgroup of ABN with less comorbities and associated symptoms.