Melanotans include melanotan I (afamelanotide) and melanotan II. Both melanotan I and II are widely abused to obtain a cosmetic tan. The melanotans are potent, non-selective melanocortin receptor agonists affecting MC1, MC3, MC4 and MC5 receptors. These receptors are responsible for many physiological systems including: pigmentation, energy, sexual function, immune system, inflammation and the cardiovascular system.
“The study is kind of a high-water mark for the field, putting different levels all together: a robust behaviour, a brain region, and a cellular basis for it,” says Richard Tsien, a neuroscientist also at Langone. Tsien has been studying the action of oxytocin on neuronal circuits in detail, by examining slices of the hippocampus, a region involved in learning and memory. In a 2013 study6 of rats, Tsien's team found that oxytocin selectively acts on a type of cell called an inhibitory interneuron in a way that quiets background chatter within the neuronal circuit. “Oxytocin improved signal transmission, almost doubling the ability of information to flow through the system,” Tsien says. In effect, it is producing more signal and less noise.

It has been noted[25] that isolated supplementation of 5-HTP may deplete or reduce the bioactivity of catecholamines such as dopamine[44][45][46] (which extends to L-Tryptphan[45]) and that this relationship also acts in reverse, with supplemental L-Tyrosine possibly able to deplete 5-HTP[47][48] and Serotonin itself,[48] which extends to supplemental L-DOPA which may reduce all intermediate of serotonin synthesis[49][50][51] although L-DOPA may also deplete L-Tyrosine (as it is merely later in the same metabolic chain).[50] Due to excessive levels of either one depleting the other, some authors have suggested that combination therapy of 5-HTP and L-Tyrosine (the furthest back in the metabolic chain while still passing rate limiting enzymes) is a potentially useful avenue for anti-depressive effects.[52]
Injected oxytocin analogues are used to induce labour and support labour in case of non-progression of parturition. It has largely replaced ergotamine as the principal agent to increase uterine tone in acute postpartum haemorrhage. Oxytocin is also used in veterinary medicine to facilitate birth and to increase milk production. The tocolytic agent atosiban (Tractocile®) acts as an antagonist of oxytocin receptors; this drug is registered in many countries to suppress premature labour between 24 and 33 weeks of gestation. It has fewer side-effects than drugs previously used for this purpose (ritodrine, salbutamol and terbutaline).
Evidence accumulated over the past decades has overturned the traditional dogma that the adult mammalian brain cannot generate new neurons. Adult neurogenesis has been identified in all vertebrate species examined thus far including humans.44-49 Newly generated neuronal cells originate from neural stem cells in the adult brain. Neural stem cells are the self-renewing, multipotent cells that generate the neuronal and glial cells of the nervous system.50 The major function of neurogenesis in adult brain seems to replace the neurons that die regularly in certain brain areas. Granule neurons in the DG continuously die and the progenitors in the subgranular zone of the DG may proliferate at the same rate as mature neuronal death to maintain a constant DG cell number.51 Similarly, the newly proliferated cells from the subventricular zone migrate and replenish the dead olfactory bulb neurons.52 Here, we focus on DG neurogenesis which is important for spatial learning and memory. In normal adult rats, newborn neural cells migrate from the subgranular zone of the DG of the hippocampus into the granule cell layer and eventually become mature granule neurons.53 These new granule neurons extend axonal processes to their postsynaptic targets54-57 and receive synaptic input.58 TBI stimulates widespread cellular proliferation in rats and results in focal neurogenesis in the DG of the hippocampus.59,60 Some of the newly generated granule neurons integrate into the hippocampus. The integration of the injury-induced neurogenic population into the existing hippocampal circuitry coincides with the time point when cognitive recovery is observed in injured animals.44
5-HTP is sometimes taken by people coming down from MDMA to relieve post-MDMA dysphoria.[8] As 5-HTP is a necessary precursor for the brain to produce more serotonin, and MDMA use depletes a person's natural serotonin levels, it is believed that taking 5-HTP after consuming MDMA will speed up serotonin production. DanceSafe claims that the anecdotal evidence is widespread and that the theory is physiologically reasonable.[9] Backing up this approach is research conducted by Wang, et al.  in 2007, which observed that MDMA-induced depletions of 5-HT (serotonin) were restored in rats after administration 5-HTP, and suggested that this approach might be clinically useful in abstinent MDMA users.[8]