HTR1A and schizophrenia: In summary, although the data that best fits with the current knowledge regarding the pathophysiology of schizophrenia is that reduced levels of muscarinic receptors contribute to a reduced inhibition of the serotonergic system and a subsequent decrease in post-synaptic serotonergic receptors, as seen with 5-HT2A and 5-HT7 receptors, this is overly simplistic given that these are not the only post-synaptic serotonergic receptors; the data regarding 5-HT1A receptors in schizophrenia is inconclusive but there are no reports of decreased levels in schizophrenia.