Social Regulation of PKMzeta in African Cichlid Fish
Male African cichlid Astatotilapia burtoni form a reversible social hierarchy and the underlying biological and physiological processes of this social plasticity are of special interest. Particularly, males are either dominant (DOM), subordinate (SUB) or transitioning (TRANs) between the two states. DOMs are brightly colored (blue or yellow), defend a territory and are reproductively active while exhibiting a repertoire of quantifiable behaviors such as fighting, chasing and courting. In contrast, a SUB male is cryptically colored, lacks a territory, displays mostly fleeing behavior and has increased stress hormone levels (Hofmann 2001; Fox et al. 1997). If a social community is instable due to changes in territory setting, variability within transitions between social states is greatly increased as compared to a stable habitat (Hofmann et al. 1999). Preliminary results indicate Protein Kinase M ζ (PKMζ), an enzyme found in brain tissue linked to learning and memory in mammals, but also is up-regulated during acute stress are differential between the social phenotypes in a stable habitat (Neumeister et al. 2011). The goals of the present study are 1.) to confirm if social stress in SUBs due to bullying by DOMS increases PKMζ levels and 2.) to test for effects of habitat instability on PKMζ. After determining social status using focal observations, males were sacrificed and brain tissue sampled for Western blot analysis of the telencephalon, a hippocampus homologue of the forebrain linked to learning and spatial memory. Results confirm PKMζ levels are decreased in DOMs vs SUBs when housed in a stable habitat. In contrast, PKM levels did not correlate with social status in subjects from an instable habitat. Taken together, social uncertainty is a powerful stressor that can influence behavior and seems to be reflected by brain levels of PKMζ.
Supported by NIH-RCMI grant numbers MD007599 (formerly RR003037) and NIDA grant R25DA032520.