Rapid Effects of Hearing Song on Catecholaminergic Activity in the Songbird Auditory Pathway

Catecholaminergic (CA) neurons innervate sensory areas and affect the processing of sensory signals. For example, in birds, CA fibers innervate the auditory pathway at each level, including the midbrain, thalamus, and forebrain. We have shown previously that in female European starlings, CA activity in the auditory forebrain can be enhanced by exposure to attractive male song for one week. It is not known, however, whether hearing song can initiate that activity more rapidly. Here, we exposed estrogen-primed, female white-throated sparrows to conspecific male song and looked for evidence of rapid synthesis of catecholamines in auditory areas. In one hemisphere of the brain, we used immunohistochemistry to detect the phosphorylation of tyrosine hydroxylase (TH), a rate-limiting enzyme in the CA synthetic pathway. We found that immunoreactivity for TH phosphorylated at serine 40 increased dramatically in the auditory forebrain, but not the auditory thalamus and midbrain, after 15 min of song exposure. In the other hemisphere, we used high pressure liquid chromatography to measure catecholamines and their metabolites. We found that two dopamine metabolites, dihydroxyphenylacetic acid and homovanillic acid, increased in the auditory forebrain but not the auditory midbrain after 30 min of exposure to conspecific song. Our results are consistent with the hypothesis that exposure to a behaviorally relevant auditory stimulus rapidly induces CA activity, which may play a role in auditory responses

Tissue engineering, stem cells, cloning, and parthenogenesis: new paradigms for therapy

Patients suffering from diseased and injured organs may be treated with transplanted organs. However, there is a severe shortage of donor organs which is worsening yearly due to the aging population. Scientists in the field of tissue engineering apply the principles of cell transplantation, materials science, and bioengineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. Both therapeutic cloning (nucleus from a donor cell is transferred into an enucleated oocyte), and parthenogenesis (oocyte is activated and stimulated to divide), permit extraction of pluripotent embryonic stem cells, and offer a potentially limitless source of cells for tissue engineering applications. The stem cell field is also advancing rapidly, opening new options for therapy. The present article reviews recent progress in tissue engineering and describes applications of these new technologies that may offer novel therapies for patients with end-stage organ failure

Tryptophan hydroxylase 2 (TPH2) gene variants associated with ADHD

Genetic and pharmacological studies have emphasised the role of serotonin 5-hydroxytryptamine (5-HT) as a possible etiologic factor in the development of attention-deficit hyperactivity disorder (ADHD). Tryptophan hydroxylase (TPH) is a rate-limiting enzyme in the biosynthesis of serotonin from tryptophan. Originally, the TPH gene was thought to be widely expressed, but a second form of TPH, TPH2, was recently identified and the TPH2 gene was found to be solely expressed in the brain. We examined eight single nucleotide polymorphisms (SNP) in the TPH2 gene for association with ADHD in 179 Irish nuclear families. Transmission disequilibrium test analysis revealed significant association between the T allele of marker rs1843809 with the disorder (Ξ = 12.2, P = 0.0006, OR = 2.36). Stratifying data by the sex of the transmitting parent showed that this association was enhanced when paternal transmission was considered (OR = 3.7). In addition, several haplotypes (all including the associated marker) were associated with ADHD. These preliminary findings suggest that TPH2 is a susceptibility locus for ADHD. Further confirmation, preferably from different ethnic groups, is required to firmly implicate TPH2 in the pathophysiology of ADHD