Ants are insects which organize themselves into behavioral castes whose regulation has been proposed to involve epigenetic processes, including histone modification. In the carpenter ant, morphologically distinct worker castes called minors and majors exhibit pronounced differences in foraging and scouting/exploratory behaviors. The authors of this paper found that these behaviors are regulated by histone acetylation.
Valproic acid, a well-known mood stabilizer for bipolar disorder and known histone deacetylase inhibitor, was able to induce more foraging behavior in these ants. Valproic acid-treated minors were also the first to act as scouts, whereas majors never scouted. Analysis of brains of scouting minor ants fed pharmacological inhibitors of CBP and histone deacetylases (HDAC) revealed hundreds of genes linked to hyperacetylated regions targeted by CBP. CBP is an acetyltransferase and transcriptional coactivator (cyclic adenosine monophosphate response element-binding protein (CREB) binding protein). Majors rarely forage, but injection of a HDAC inhibitor or small interfering RNAs against the HDAC Rpd3 into young major brains induced and sustained foraging in a CBP-dependent manner. The authors suggest that behavioral plasticity in animals may be regulated in an epigenetic manner via histone modification. Whether the bipolar drug, valproic acid, has similar effects in mammals requires further investigation.
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Simola DF, Graham RJ, Brady CM, Enzmann BL, Desplan C, Ray A, Zwiebel LJ, Bonasio R, Reinberg D, Liebig J, Berger SL: Epigenetic (re)programming of caste-specific behavior in the ant Camponotus floridanus. Science 351(6268): pii: aac6633. doi: 10.1126/science.aac6633 [2016 Jan 1].
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http://www.ncbi.nlm.nih.gov/pubmed/26722000

http://news.sciencemag.org/biology/2015/12/bipolar-drug-turns-foraging-ants-scouts