HTR1A and post-traumatic stress disorder: Moreover, the density of 5HT1A receptors has also been shown to be upregulated in a rat model of PTSD suggesting the involvement of 5HT1A receptors in modulating the anxiety phenotype of PTSD (Luo et al. 2011), and these outcomes were consistent with the neuroimaging findings in PTSD patients (Sullivan et al. 2013).