Characterization of receptors for calcitonin gene-related peptide and adrenomedullin on the guinea-pig vas deferens

1. The receptors which mediate the effects of calcitonin gene-related peptide (CGRP), amylin and adrenomedullin on the guinea-pig vas deferens have been investigated. 2. All three peptides cause concentration dependant inhibitions of the electrically stimulated twitch response (pD 2s for CGRP, amylin and adrenomedullin of 7.90 ± 0.11, 7.70 ± 0.19 and 7.25 ± 0.10 respectively). 3. CGRP 8-37 (1 μM) and AC187 (10 μM) showed little antagonist activity against adrenomedullin. 4. Adrenomedullin 22-52 by itself inhibited the electrically stimulated contractions of the vas deferens and also antagonized the responses to CGRP, amylin and adrenomedullin. 5. [ 125I]-adrenomedullin labelled a single population of binding sites in vas deferens membranes with a pIC 50 of 8.91 and a capacity of 643 fmol mg -1. Its selectivity profile was adrenomedullin > AC187 > CGRP = amylin. It was clearly distinct from a site labelled by [ 125I]-CGRP (pIC 50 = 8.73, capacity = 114 fmol mg -1, selectivity CGRP > amylin = AC187 > adrenomedullin). [ 125I]-amylin bound to two sites with a total capacity of 882 fmol mg -1. 6. Although CGRP has been shown to act at a CGRP 2 receptor on the vas deferens with low sensitivity to CGRP 8-37, this antagonist displaced [ 125I]-CGRP with high affinity from vas deferens membranes. This affinity was unaltered by increasing the temperature from 4°C to 25°C, suggesting the anomalous behaviour of CGRP 8-37 is not due to temperature differences between binding and functional assays.

Eating behaviours of preadolescent children over time:stability, continuity and the moderating role of perceived parental feeding practices

The links between childhood eating behaviours and parental feeding practices are well-established in younger children, but there is a lack of research examining these variables in a preadolescent age group, particularly from the child's perspective, and longitudinally. This study firstly aimed to examine the continuity and stability of preadolescent perceptions of their parents' controlling feeding practices (pressure to eat and restriction) over a 12 month period. The second aim was to explore if perceptions of parental feeding practices moderated the relationship between preadolescents' eating behaviours longitudinally. Two hundred and twenty nine preadolescents (mean age at recruitment 8.73 years) completed questionnaires assessing their eating behaviours and their perceptions of parental feeding practices at two time points, 12 months apart (T1 and T2). Preadolescents' perceptions of their parental feeding practices remained stable. Perceptions of restriction and pressure to eat were continuous. Perceptions of parental pressure to eat and restriction significantly moderated the relationships between eating behaviours at T1 and T2. The findings from this study suggest that in a preadolescent population, perceptions of parental pressure to eat and restriction of food may exacerbate the development of problematic eating behaviours.