Neuroendocrine mechanisms underlying sensory integration of social signals.

Individuals integrate information about their environment into adaptive behavioural responses, yet how different sensory modalities contribute to these decisions and where in the brain this integration occurs is not well understood. We presented male cichlid fish (Astatotilapia burtoni) with sensory information in three social contexts: intruder challenge, reproductive opportunity and a socially neutral situation. We then measured behavioural and hormonal responses along with induction of the immediate early gene c-Fos in candidate forebrain regions. In the intruder challenge context, males were exposed to either a visual stimulus of a dominant male, the putative male pheromone androstenedione, or both. We found that, compared to the neutral context, a visual stimulus was necessary and sufficient for an aggressive response, whereas both chemical and visual stimuli were needed for an androgen response. In the reproductive opportunity context, males were exposed to either a visual stimulus of a receptive female, a progesterone metabolite (female pheromone) only, or both. We further found that the visual stimulus is necessary and sufficient for an androgen response in the reproductive opportunity context. In the brain, we observed c-Fos induction in response to a visual challenge stimulus specifically in dopaminergic neurones of area Vc (the central region of the ventral telencephalon), a putative striatal homologue, whereas presentation of a chemical stimulus did not induce c-Fos induction in the intruder challenge context. Our results suggest that different sensory cues are processed in a social context-specific manner as part of adaptive decision-making processes.

Androgens coordinate neurotransmitter-related gene expression in male whiptail lizards.

Sex steroid hormones coordinate neurotransmitter systems in the male brain to facilitate sexual behavior. Although neurotransmitter release in the male brain has been well documented, little is known about how androgens orchestrate changes in gene expression of neurotransmitter receptors. We used male whiptail lizards (Cnemidophorus inornatus) to investigate how androgens alter neurotransmitter-related gene expression in brain regions involved in social decision making. We focused on three neurotransmitter systems involved in male-typical sexual behavior, including the N-methyl-d-aspartate (NMDA) glutamate receptor, nitric oxide and dopamine receptors. Here, we show that in androgen-treated males, there are coordinated changes in neurotransmitter-related gene expression. In androgen-implanted castrates compared with blank-implanted castrates (control group), we found associated increases in neuronal nitric oxide synthase gene expression in the nucleus accumbens (NAcc), preoptic area and ventromedial hypothalamus, a decrease of NR1 gene expression (obligate subunit of NMDA receptors) in the medial amygdaloid area and NAcc and a decrease in D1 and D2 dopamine receptor gene expression in the NAcc. Our results support and expand the current model of androgen-mediated gene expression changes of neurotransmitter-related systems that facilitate sexual behavior in males. This also suggests that the proposed evolutionarily ancient reward system that reinforces sexual behavior in amniote vertebrates extends to reptiles.

Neuronal nitric oxide synthase as a substrate for the evolution of pseudosexual behaviour in a parthenogenetic whiptail lizard.

The evolution of neuroendocrine mechanisms governing sex-typical behaviour is poorly understood. An outstanding animal model is the whiptail lizard (Cnemidophorus) because both the ancestral and descendent species still exist. The ancestral little striped whiptail, Cnemidophorus inornatus, consists of males and females, which exhibit sex-specific mating behaviours. The descendent desert grassland whiptail, Cnemidophorus uniparens, consists only of females that alternately exhibit both female-like and male-like pseudosexual behaviour. Castrated male C. inornatus will mount a conspecific in response to exogenous androgen, although some are also sensitive to progesterone. This polymorphism in progesterone sensitivity in the ancestral species may have been involved in evolution of progesterone-mediated male-typical behaviour in the descendant unisexual lizards. We tested whether progesterone activates a typically androgenic signalling pathway by investigating hormonal regulation of neuronal nitric oxide synthase (nNOS) using in situ hybridisation and NADPH diaphorase histochemistry, a stain for nNOS protein. NADPH diaphorase is widely distributed throughout the brain of both species, although only in the periventricular nucleus of the preoptic area (pvPOA) are there differences between mounting and non-mounting individuals. The number of cells expressing nNOS mRNA and NADPH diaphorase is higher in the pvPOA of individuals that mount in response to progesterone or androgen. Furthermore, the nNOS promoter has both androgen and progesterone response elements, and NADPH diaphorase colocalises with the progesterone receptor in the pvPOA. These data suggest that a polymorphism in progesterone sensitivity in the sexual ancestor reflects a differential regulation of nNOS and may account for the male-typical behaviour in unisexual whiptail lizards.

Workload and short-term outcome of babies weighing 2,500 grams or more at birth admitted to the paediatric unit of the Rotunda Hospital.

BACKGROUND: Audit is important in ensuring adequate use of resources and maintaining optimum standards of care. Most of the emphasis in neonatal audit is focused on very low birth weight infants. However, term and near-term infants account for a significant proportion of the workload in neonatal units and warrant regular audit. In addition, audit of these infants may be useful as a marker of the organisation of the perinatal service. METHODS: A retrospective audit was performed of all infants with birth weights greater than or equal to 2,500 grams admitted to the neonatal department in the first week of life over a two-year period, examining mode of delivery, level of care, duration of stay, diagnosis and short-term outcome. RESULTS: Eight hundred and seventy infants were admitted greater than or equal to 2,500 grams birth weight, 54% of all neonatal admissions, during the study period. Six hundred and eighty seven of these infants were admitted in the first week of life and were included in the study; this was 5.8% of infants born with a birth weight 2500 grams or more. Infants born by caesarean section were twice as likely to require admission (9.8%) compared with infants born by vaginal delivery (4.5%). The median length of stay was 3 days (3 hours to 45 days). One hundred and six (15.4%) infants required level 1 or level 2 care. One hundred and eleven infants received normal care, only. Most of these infants were admitted for maternal or social reasons. Other common reasons for admission were jaundice, respiratory disease, neonatal abstinence syndrome and congenital abnormality. Forty-one infants required transfer to another hospital, most commonly for surgical or cardiac conditions. Six infants died after admission. However, only one normally formed infant delivered in our hospital died prior to discharge or transfer. One infant was born at home and four infants who had a lethal congenital abnormality are known to have died following transfer. CONCLUSION: Term and near-term infants account for a significant proportion of neonatal admissions and deserve regular audit. Many admissions are potentially avoidable. Survival for infants weighing 2,500 grams or greater is excellent. Only one normally formed infant died following admission during the study period. The number of "social" admissions of "well" infants highlighted by this study reflects poorly on the services available for well infant whose mothers are unable to care for them for whatever reason. We recommend regular audit of these infants in order to ensure efficient use of neonatal resources and to ensure optimum levels of neonatal intensive care.