To investigate whether the newborn neurons generated in the DG are capable of projecting their axons into the CA3 region of the hippocampus after TBI, we stereotactically injected a fluorescent tracer, 1,1″-dioleyl-3,3,3″,3″-tetramethylindocarbocyanine methanesulfonate (Dil, Delta 9-DiI; AnaSpec, San Jose, CA) into the ipsilateral CA3 region (stereotaxic coordinates AP, -3.6 mm bregma, ML, 3.6 mm, DV, 3.0 mm, Paxinos and Watson, 1994) at day 28 after TBI. BrdU (100mg/kg, ip) was injected i.p. daily starting at day 1 after TBI for 10 days to label newly generated cells. One week after DiI injection (i.e., 35 days after TBI), the animals were anesthetized and sacrificed. Their brains were fixed in 4% paraformaldehyde. The brain was cut into seven equally spaced 2-mm coronal blocks using a rat brain matrix. The brain blocks containing the hippocampus were processed for vibratome sections (100 μm) followed by BrdU staining. BrdU and DiI labeling in the hippocampus on brain sections was analyzed with a Bio-Rad MRC 1024 (argon and krypton) laser-scanning confocal imaging system mounted onto a Zeiss microscope (Bio-Rad, Cambridge, MA). Co-localization of BrdU-positive nuclei within retrogradely DiI-labeled granule cells was found, indicating that newborn granule neurons extend axons into the CA3 region that are capable of retrogradely transporting DiI from the CA3 to their cell bodies within the DG after TBI (Fig.2). This finding suggests that newborn granule neurons may be incorporated into functional hippocampal circuitry after TBI.
When combined with antidepressants of the MAOI or SSRI class, very high parenteral doses of 5-HTP can cause acute serotonin syndrome in rats. It is unclear if such findings have clinical relevance, as most drugs will cause serious adverse events or death in rodents at very high doses. In humans 5-HTP has never been clinically associated with serotonin syndrome, although 5-HTP can precipitate mania when added to an MAOI.
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
Osteoclast differentiation was assessed by tartrate-resistant acid phosphatase (TRAP) staining and activity. After 5 days of culture, cells were stained for TRAP kit using a leukocyte acid phosphatase kit (Sigma Aldrich, St Louis, MO, USA). Cells with three or more nuclei were counted as multinucleated mature osteoclasts. To measure TRAP activity, cells were fixed with 10% formalin for 10 min and 95% ethanol for 1 min, and then 100 μl of citrate buffer (50 mM, pH 4.6) containing 10 mM sodium tartrate and 5 mM p-nitrophenylphosphate (Sigma-Aldrich) was added to the wells containing fixed cells in the 48-well plates. After incubation for 1 h, enzyme reaction mixtures in the wells were transferred to new plates containing an equal volume of 0.1 N NaOH. Absorbance was measured at 410 nm using a microplate reader.
Oxytocin has been of keen interest to neuroscientists since the 1970s, when studies started to show that it could drive maternal behaviour and social attachment in various species. Its involvement in a range of social behaviours2, including monogamy in voles, mother–infant bonding in sheep, and even trust between humans, has earned it a reputation as the 'hug hormone'. “People just concluded it was a bonding molecule, a cuddling hormone, and that's the pervasive view in the popular press,” says Larry Young, a neuroscientist at Emory University in Atlanta, Georgia, who has been studying the molecule since the 1990s.
TB-500 and Thymosin Beta-4 are not exactly the same, although you’ll often see the two names used interchangeably in the peptide world (AKA broscience bodybuilding forums). It’s much harder to get your hands on true Thymosin Beta-4, whether for research use, equine enhancement, athletic performance enhancement or bodybuilding. But TB-500’s peptide sequence shares most of the properties of Thymosin Beta-4, and it’s more economical to produce, thus easier to find.
She recruited 31 men* and asked them to sniff either an oxytocin nasal spray or another spray with the same ingredients minus oxytocin – a placebo. A few weeks later, the sprays were swapped so that the men who took oxytocin now took the placebo, and vice versa. At the time, neither the scientists nor the volunteers knew which was which – that was only revealed after the experiment was over.
The short half-life (<2h) of 5-HTP may inherently limit the therapeutic potential of 5-HTP, as the systemic 5-HTP exposure levels will fluctuate substantially, even with relatively frequent dosing. Such exposure fluctuations are usually associated with increased adverse event burden, resulting from Cmax drug spikes, and decreased clinical efficacy resulting from sub-therapeutic exposure for large parts of the day. It has been proposed that 5-HTP dosage forms achieving prolonged delivery would be more effective, as is generally the situation with short-acting active pharmaceutical ingredients.