Neurological investigation of sadistic humor

Sadistic humor is one of the major emotions that underlies bullying behavior. The emotion of sadistic humor is not the same emotion as plain, non-sadistic humor; sadistic humor is a mixture of basic humor with the sadistic disruptive emotions. I have wondered why it is that those particular emotions mix together so readily.

The sadistic disruptive emotions are mediated by the receptors of the nonapeptide neurotransmitters- oxytocin and vasopressin (despite the popular lies going around about oxytocin). But there has been little investigation into the neurology of the humor emotion, which causes laughing. There must be a neurological link between those emotions.

It is known that humor is caused by cannabinoids, nitrous oxide gas, and serotonin, so it is initially unclear what particular receptor causes humor. Cannabinoids have been discovered to increase the activity of 5-ht2a receptors (receptors that contain '5-ht' in their name are serotonin receptors), and some effects of nitrous oxide have been shown to be mediated by 5-ht2a and/or 5-ht2c receptors. I therefore conclude that the 5-ht2a receptor is most likely the main humor receptor, though the 5-ht2c receptor is probably also involved because it is so often co-expressed with 5-ht2a receptors.

So then, there would in theory be a close link between those particular serotonin receptors and nonapeptide activity, thus creating sadistic humor. And indeed, just such a link has been discovered. This research paper: http://www.ncbi.nlm.nih.gov/pubmed/12716407 states: "Infusion of agonists selective for the 5-HT2A + 2C receptor increased vasopressin mRNA in the [paraventricular nucleus of the hypothalamus]" and "stimulation with ... 5-HT agonists increases mRNA expression of oxytocin in the [paraventricular nucleus] and the [supraoptic nucleus] via stimulation of ... 5-HT2A and 5-HT2C receptors".

After doing more research, I believe that it is more likely that the link between 5-ht2a and/or 5-ht2c receptors and nonapeptide production and secretion is due to a 'stress-induced' response that destabilizes the emotions, in which case the 5-ht2a and/or 2c receptors would produce an emotion related to crying, rather than humor. That is supported by the fact that the research paper that I linked to in the original post states that the interaction involves corticotropin-releasing hormone (a chemical that is related to depression), and the facts that 5-ht2c receptor activity decreases dopamine (the neurotransmitter of pleasure), and elevated 5-ht2a levels have been found in the brains of people who died by suicide (and may therefore be related to depression).

So if that is the case, then I must look elsewhere for the neurological bases of humor and sadistic humor. Cannabinoid receptors are also a major candidate for the humor emotion, so I suspected that they interact with the nonapeptides. I found multiple research papers which link cannabinoid activity to nonapeptide activity in the hypothalamus (a major emotion center), here:
http://www.ncbi.nlm.nih.gov/pubmed/18655878 ,
http://www.ncbi.nlm.nih.gov/pubmed/21988161 ,
http://www.frontiersin.org/10.3389/conf ... t_abstract .