TRAINOR, B. C.; HOFMANN, H. A.; Harvard University; Harvard University: Interactions between the Neuropeptide Somatostatin and Social Plasticity in the African Cichlid Fish Astatotilapia burtoni

Hypothalamic neuropeptides play an important role in the regulation of social behavior. Recent research has documented important effects of somatostatin (SS) on dominance behavior, a neuropeptide known previously for its inhibitory effects on somatic growth. An earlier study found that in the cichlid fish Astatotilapia (Haplochromis) burtoni, dominant territorial males had larger SS immunoreactive cells in the preoptic area of the hypothalamus compared to subordinate nonterritorial males. Increased SS neuron size could be due to increased SS production and release or inhibition of SS release. We are testing these hypotheses by manipulating SS function with injections of cyclo-somatostatin (cSS), a SS antagonist. Preliminary results indicate that cSS increased aggression in territorial males compared to saline treated males, suggesting that territorial males have inhibited SS release. To examine variations in other aspects of SS function we have begun cloning genes for the SS peptide and SS receptors. These sequences will be used to design primers for quantitative real-time PCR to compare gene expression in territorial and nonterritorial males. Five different SS receptor sub-types have been identified, and the differential expression of these subtypes is thought to regulate functional specificity of SS. Comparing gene expression of these receptors in territorial and non-territorial males will provide insight on which receptor sub-types mediate the effects of SS on dominance interactions.