R D Craven | PubMed Health

PubMed1999

Effect of a long-term low tryptophan diet on the prolactin responses to the 5-HT1A and 5-HT2C agonists, 8-OH-DPAT and mCPP in the male rat.

The study was undertaken to assess the long term effects of tryptophan (TRP) depletion through diet on the prolactin (PRL) responses to the serotonin (5-hydroxytryptophan, 5-HT) agonists m-chlorophenyl-piperazine (mCPP) and 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) in the male rat. The low TRP diet caused significant reductions in both plasma total TRP and brain cortical 5-HT content together with a significant increase in the PRL responses to mCPP. In contrast the PRL responses to 8-OH-DPAT in animals on the low TRP diet for 1 week and 6 weeks were similar to control rats. However, a small but significant increase in PRL was observed at 2 min after dosing in the 1-week group. At the same time the 3H-8-OH-DPAT binding parameters, Kd and Bmax, were similar in both control and TRP depleted animals. The results confirm that long-term TRP depletion causes a deficiency of brain TRP and a subsequent reduction of brain 5-HT. This is associated with an enhanced PRL response to mCPP probably resulting from a functional up-regulation of post-synaptic 5-HT2C receptors. The small or transient changes brought about by long-term TRP depletion on post-synaptic 5-HT1A receptors, suggests that these receptors may be less susceptible to 5-HT depleting effects than the 5-HT2C subtype.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1998

QCM response to solvated, tethered macromolecules.

When the quartz crystal microbalance (QCM) is operated in contact with solution and used to detect inertia increases caused by macromolecules binding to its surface, resonance frequency shifts are reported in the literature to be greater than, less than, and the same as an identical macromolecular mass would cause as a dry layer. A previous report of wet and dry M13 DNA giving the same, linear frequency versus mass response is examined. The M13 data are shown to follow the reciprocal of the square root of mass, not the reported linear relationship. New experiments on RNA duplexes oscillated in solution are reported. A lossy polymer layer is placed between the QCM and RNA. When changes in density, viscosity, and included water are eliminated, the response remains linear for a constant adlayer thickness. The expectation that response per unit mass should decrease with distance from the QCM surface is demonstrated. Total decoupling of mass lying beyond the acoustic overlayer is also demonstrated. The present results are placed in context with recently published results from a study of progressively thicker protein layers bound to the QCM.

Biopolymers↗