Evidence for this role of oxytocin come from two types of experiments. First, infusion of oxytocin into the ventricles of the brain of virgin rats or non-pregnant sheep rapidly induces maternal behavior. Second, administration into the brain of antibodies that neutralize oxytocin or of oxytocin antagonists will prevent mother rats from accepting their pups. Other studies support the contention that this behavioral effect of oxytocin is broadly applicable among mammals.
Silencing of the Tβ4 or Wnt5a gene was achieved by transfecting cells with small interfering RNA (siRNA). Cells were transfected with Tβ4 or Wnt5a siRNAs (30 nM) for 24 hours using Lipofectamine 2000 (Invitrogen, Carlsbad, CA, USA) according to the manufacturer's instructions. Cells were transfected with Silencer negative control siRNA using the same protocol.
Interestingly, there are numerous differences in the biology of teleosts and mammals, as well as specific differences in cardiomyocyte cellular structure and anatomy, all of which might contribute to regenerative variability. Unlike mammals, zebrafish can grow throughout most of adulthood, a phenomenon called “indeterminate growth” (Jordan, 1905). In fact, their growth can be affected markedly by changes in nutrition and population density (Goldsmith et al., 2006). It is thus possible that the capacity to replace cardiac tissue rapidly in teleosts has been retained in evolution as a function of the need for robust animal and cardiac growth. Indeed, a recent study has found that experimentally-induced adult cardiac growth in zebrafish is hyperplastic, and appears to rely on the same signals present or required during cardiac regeneration (Wills et al., 2008).
In regards to interventions, one study in treatment resistant depressed persons that combination therapy of 5-HTP with Carbidopa noted that 43 out of 99 (43.4%) patients improved with an average 200mg (variable 50-600mg) dosage of 5-HTP. It has been noted that since Cardidopa is a peripheral decarboxylase inhibitor that can prevent metabolism of monoamines including serotonin that these results are unlikely to reflect monotherapy with 5-HTP, despite being within the 30-45% range sometimes seen with the placebo effect.
5-HTP is decarboxylated to serotonin (5-hydroxytryptamine or 5-HT) by the enzyme aromatic-L-amino-acid decarboxylase with the help of vitamin B6. This reaction occurs both in nervous tissue and in the liver. 5-HTP crosses the blood–brain barrier, while 5-HT does not. Excess 5-HTP, especially when administered with vitamin B6, is thought to be metabolized and excreted.