Further research confirms that the HPA is regulated by methylation of the stress-hormone, glucocorticoid receptor (GR) gene.  Methylation of the GR gene is different in the offspring of the two maternal types and cross-fostering modifies the methylation. Epigenetic modifications are potentially reversible, so the researchers set about reversing GR methylation using a drug (demethylating agent) to see if this could reverse the stressed HPA behaviour of the pups nurtured by low-LG rats.

The answer affirms the effectiveness of drug treatment to influence the stress response and yields another interesting observation; the behaviour is reversible (through drug treatment) even when the pups have become adults. This fascinating work not only identifies an epigenetic link between parenting and offspring behaviour illustrating how dynamically nature gets nurtured throughout life, but serves as a springboard for human studies.