Nucleus Accumbens GABAergic Inhibition Generates Intense Eating and Fear That Resists Environmental Retuning and Needs No Local Dopamine.

Nucleus accumbens GABAergic inhibition generates intense eating and fear that resists environmental retuning and needs no local dopamine.

Eur J Neurosci. 2013 Mar 31;
Richard JM, Plawecki AM, Berridge KC

Intense fearful behavior and/or intense appetitive eating behavior can be generated by localized amino acid inhibitions along a rostrocaudal anatomical gradient within medial shell of nucleus accumbens of the rat. This can be produced by microinjections in medial shell of either the ?-aminobutyric acid (GABA)A agonist muscimol (mimicking intrinsic GABAergic inputs) or the AMPA (?-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) antagonist DNQX (6,7-dinitroquinoxaline-2,3-dione), disrupting corticolimbic glutamate inputs). At rostral sites in medial shell, each drug robustly stimulates appetitive eating and food intake, whereas at more caudal sites the same drugs instead produce increasingly fearful behaviors such as escape, distress vocalizations and defensive treading (an antipredator behavior rodents emit to snakes and scorpions). Previously we showed that intense motivated behaviors generated by glutamate blockade require local endogenous dopamine and can be modulated in valence by environmental ambience. Here we investigated whether GABAergic generation of intense appetitive and fearful motivations similarly depends on local dopamine signals, and whether the valence of motivations generated by GABAergic inhibition can also be retuned by changes in environmental ambience. We report that the answer to both questions is ‘no’. Eating and fear generated by GABAergic inhibition of accumbens shell does not need endogenous dopamine. Also, the appetitive/fearful valence generated by GABAergic muscimol microinjections resists environmental retuning and is determined almost purely by rostrocaudal anatomical placement. These results suggest that nucleus accumbens GABAergic release of fear and eating are relatively independent of modulatory dopamine signals, and more anatomically pre-determined in valence balance than release of the same intense behaviors by glutamate disruptions. HubMed – eating


Bergmann’s rule across the equator: a case study in Cerdocyon thous (Canidae).

J Anim Ecol. 2013 Apr 3;
Martinez PA, Marti DA, Molina WF, Bidau CJ

The variation in cranial size of the crab-eating fox Cerdocyon thous was analysed in relation to latitude and several environmental variables throughout its distribution in South America. We tested the existence of clines to determine whether this canid follows Bergmann’s rule to the north and south of the Equator. Also, using niche modelling, we analysed whether the climatic changes during the last glaciation could have influenced Bergmann’s rule in this species. We quantified the size of the cranium of C. thous (n = 300). The data were divided into two groups: (i) south of the Equator (n = 163) and (ii) north of the Equator (n = 137). We performed correlations, OLS regressions and simultaneous autoregressions to analyse the relationship between the variation in size and different geographic and environmental variables. Data of occurrence (n = 594) together with ambient variables from the present and the last glacial maximum (LGM) were used to predict the occurrence of C. thous with the implementation of the maximum entropy method. Present-day and historical distribution maps were obtained. The variation in the size of the cranium of C. thous showed two trends. In the south of Equator, we observed that the size of the skull shows an inverse relationship with temperature-related variables and a positive one with precipitation, while in north of the Equator, we observed the opposite relationship. Populations south of the Equator follow Bergmann’s rule showing increasing size with increasing latitude. To the north of the Equator, a non-Bergmannian pattern occurs because size decreases with increasing latitude. Niche modelling showed two present-day groupings in South America, one north of Amazonia and the other south. However, for the period of the LGM, four groups emerged, possibly related to the four subspecies presently described for C. thous. Therefore, it is possible that the observed pattern – southern populations following Bergmann’s rule while northern populations reflecting the opposite – has been influenced by the events that occurred during the LGM that could have led to the differentiation of populations. HubMed – eating


Disordered Eating Behaviors in Youth with Type 1 Diabetes: Prospective Pilot Assessment Following Initiation of Insulin Pump Therapy.

Diabetes Technol Ther. 2013 Apr 3;
Markowitz JT, Alleyn CA, Phillips R, Muir A, Young-Hyman D, Laffel LM

Abstract Background: There is risk for disordered eating behaviors in type 1 diabetes, especially related to insulin manipulation. Implementation of insulin pump therapy may encourage either normalization of eating behaviors or a greater focus on food intake due to renewed emphasis on carbohydrate counting. There is need for prospective studies to assess disordered eating behaviors upon implementation of pump therapy using diabetes-specific measurement tools. Subjects and Methods: In a multicenter pilot study, 43 youth with type 1 diabetes, 10-17 years old, were assessed prior to pump initiation and after 1 and 6 months of pump therapy. Youth completed the Diabetes-specific Eating Problems Survey-Revised (DEPS-R), a validated measure of risk for both diabetes-specific and general disordered eating behaviors. Results: Youth (45% female), 13.3 years old with diabetes for 2.1 years, had a mean hemoglobin A1c of 8.3±1.3% (68±14.5?mmol/mol) at baseline. DEPS-R scores decreased over time (P=0.01). Overall rate of high risk for eating disorders was low. Overweight/obese youth endorsed more disordered eating behaviors than normal-weight participants. DEPS-R scores were correlated with z-score for body mass index at all three time points and with hemoglobin A1c after 1 and 6 months. Hemoglobin A1c did not change significantly over the 6 months and was higher in overweight/obese compared with normal-weight participants. Conclusions: Initiation of insulin pump therapy was associated with diminished endorsement of disordered eating behaviors in youth with type 1 diabetes. Longer follow-up studies are needed to assess the impact of insulin pump therapy on glycemic control, weight status, and disordered eating behaviors in this vulnerable population. HubMed – eating



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