The Organization of the Second Optic Chiasm of the Drosophila Optic Lobe

Visual pathways from the compound eye of an insect relay to four neuropils, successively the lamina, medulla, lobula, and lobula plate in the underlying optic lobe. Among these neuropils, the medulla, lobula, and lobula plate are interconnected by the complex second optic chiasm, through which the anteroposterior axis undergoes an inversion between the medulla and lobula. Given their complex structure, the projection patterns through the second optic chiasm have so far lacked critical analysis. By densely reconstructing axon trajectories using a volumetric scanning electron microscopy (SEM) technique, we reveal the three-dimensional structure of the second optic chiasm of Drosophila melanogaster, which comprises interleaving bundles and sheets of axons insulated from each other by glial sheaths. These axon bundles invert their horizontal sequence in passing between the medulla and lobula. Axons connecting the medulla and lobula plate are also bundled together with them but do not decussate the sequence of their horizontal positions. They interleave with sheets of projection neuron axons between the lobula and lobula plate, which also lack decussations. We estimate that approximately 19,500 cells per hemisphere, about two thirds of the optic lobe neurons, contribute to the second chiasm, most being Tm cells, with an estimated additional 2,780 T4 and T5 cells each. The chiasm mostly comprises axons and cell body fibers, but also a few synaptic elements. Based on our anatomical findings, we propose that a chiasmal structure between the neuropils is potentially advantageous for processing complex visual information in parallel. The EM reconstruction shows not only the structure of the chiasm in the adult brain, the previously unreported main topic of our study, but also suggest that the projection patterns of the neurons comprising the chiasm may be determined by the proliferation centers from which the neurons develop. Such a complex wiring pattern could, we suggest, only have arisen in several evolutionary steps.

Prostaglandin E2 depresses GABA release onto parvocellular neuroendocrine neurones in the paraventricular nucleus of the hypothalamus via presynaptic receptors

Inflammation-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis and the ensuing release of anti-inflammatory glucocorticoids are critical for the fine-tuning of the inflammatory response. This immune-induced neuroendocrine response is in large part mediated by prostaglandin E₂ (PGE₂ ), the central actions of which ultimately translate into the excitation of parvocellular neuroendocrine cells (PNCs) in the hypothalamic paraventricular nucleus. However, the neuronal mechanisms by which PGE₂ excites PNCs remain incompletely understood. In the present study, we report that PGE₂ potently depresses GABAergic inhibitory synaptic transmission onto PNCs. Using whole-cell patch clamp recordings obtained from PNCs in ex vivo hypothalamic slices from rats, we found that bath application of PGE₂ (0.01-100 μmol L^-1 ) concentration-dependently decreased the amplitude of evoked inhibitory postsynaptic currents (eIPSCs) with maximum effects at 10 μmol L^-1 . The PGE₂ -mediated depression of eIPSCs had a rapid onset and was long-lasting, and also was accompanied by an increase in paired pulse ratio. In addition, PGE₂ decreased the frequency but not the amplitude of both spontaneous IPSCs and miniature IPSCs. These results collectively indicate that PGE₂ acts at a presynaptic locus to decrease the probability of GABA release. Using pharmacological approaches, we also demonstrated that the EP3 subtype of the PGE₂ receptor mediated the actions of PGE₂ on GABA synapses. Taken together, our results show that PGE₂ , via actions of presynaptic EP3 receptors, potently depresses GABA release onto PNCs, providing a plausible mechanism for the disinhibition of HPA axis output during inflammation.

A resource for the Drosophila antennal lobe provided by the connectome of glomerulus VA1v

Using FIB-SEM we report the entire synaptic connectome of glomerulus VA1v of the right antennal lobe in Drosophila melanogaster. Within the glomerulus we densely reconstructed all neurons, including hitherto elusive local interneurons. The fruitless-positive, sexually dimorphic VA1v included >11,140 presynaptic sites with ~38,050 postsynaptic dendrites. These connected input olfactory receptor neurons (ORNs, 51 ipsilateral, 56 contralateral), output projection neurons (18 PNs), and local interneurons (56 of >150 previously reported LNs). ORNs are predominantly presynaptic and PNs predominantly postsynaptic; newly reported LN circuits are largely an equal mixture and confer extensive synaptic reciprocity, except the newly reported LN2V with input from ORNs and outputs mostly to monoglomerular PNs, however. PNs were more numerous than previously reported from genetic screens, suggesting that the latter failed to reach saturation. We report a matrix of 192 bodies each having >50 connections; these form 88% of the glomerulus' pre/postsynaptic sites.

Undergraduate students' perceptions of child sexual abuse: effects of age, sex, and gender-role attitudes

OBJECTIVE

The present study examined how sex of the child and the adult and age of the child influence perceptions regarding the abusiveness of adult-child sexual interactions and attributions of blame and responsibility to the adult in such incidents. The relationship of gender-role attitudes to perceptions of child sexual abuse was also investigated.

METHOD

Undergraduate students (N = 404) read one of eight vignettes depicting a sexual interaction between a child and an adult in which sex of the child, age of the child, and sex of the adult were manipulated. Respondents then answered questions regarding their perceptions of the abusiveness of the incident and attributions of responsibility and blame to the adult.

RESULTS

Scenarios depicting a 15-year-old were rated as less abusive, and less responsibility was attributed to the adult, relative to vignettes involving a 7-year-old. Respondents also rated scenarios depicting opposite-sex interactions as less abusive relative to scenarios describing same-sex interactions. When vignettes depicted a 15-year-old, less blame was attributed to the adult relative to when vignettes depicted a 7-year-old with an adult of either sex, with the least amount of blame being attributed to the adult involved with an adolescent of the opposite-sex. Gender-role attitudes were not significantly related to ratings of abusiveness or attributions of responsibility and blame.

CONCLUSIONS

These findings suggest that age of the child may influence ratings of abusiveness and attributions of responsibility and blame. Ratings of abusiveness and attributions of blame also appear to be influenced by the sex pairing in the interaction.

The prevalence of trauma and its relationship to borderline personality symptoms and self-destructive behaviors in a primary care setting

OBJECTIVE

To determine the prevalence of five types of trauma and their relationship to borderline personality symptoms and self-destructive behaviors in female subjects recruited from a primary care setting.

DESIGN

Consecutive sample.

METHOD

Subjects completed a lengthy research booklet.

SETTING

Primary care, outpatient, health maintenance organization setting.

PATIENTS

One hundred fifty-two consecutive women, aged 18 to 45 years, who were scheduled for routine gynecological care by a female family physician.

MAIN OUTCOME MEASURES

Measures included a demographic questionnaire, a trauma questionnaire (ie, sexual, physical, and emotional abuse, physical neglect, and witnessing of violence), the Borderline Personality Scale of the Personality Diagnostic Questionnaire-Revised; and the Self-Harm Inventory.

RESULTS

Traumatic experiences were reported by 70.7% of the subjects (25.8%, sexual abuse; 36.4%, physical abuse; 43.7%, emotional abuse; 9.3%, physical neglect; and 43.0%, witnessing of violence). There was a significant correlation between the acknowledged number of abuse categories and borderline personality symptoms (r = .36, P = .01) as well as self-destructive behaviors (r = .43, P = .01). Sexual abuse and witnessing of violence were most associated with borderline personality symptoms; sexual abuse, physical abuse, and witnessing of violence were most associated with self-destructive behaviors.

CONCLUSIONS

This study provides further evidence that abuse is a nonspecific but contributory factor to psychopathologic processes, in particular borderline personality symptoms and self-destructive behaviors.