PubMed · 9630740
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1998. 5-hydroxytryptophan.. https://pubmed.ncbi.nlm.nih.gov/9630740/
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The activation of rostrally projecting serotonergic (5-HT) neurons by acute sound stress is blocked by exogenous administration of the tridecapeptide neurotensin (NT). 5-HT neurons respond to acute sound stress within the median raphe nucleus (MRN), but not within the dorsal raphe nucleus or hindbrain regions. By use of the NT antagonist, SR 48692, the present study examines the involvement of endogenous NT in modulating the preferential activation of MRN 5-HT neurons by sound stress, and extends the findings with sound stress to two other stressors (swim and tail shock). Activation is determined from the enhanced accumulation of 5-hydroxytryptophan (5-HTP) from various brain regions over basal after inhibition of aromatic amino acid decarboxylase. The NT antagonist, SR 48692, enhances the stress activation of MRN 5-HT neurons and its projections without changing 5-HTP accumulation under basal conditions. Thus, the antagonist, SR 48692, unmasks the action of endogenous NT-containing neurons indicating that they become activated by stress and serve to attenuate the stress-induced response of MRN 5-HT neurons.
Tropomyosin is a coiled-coil protein that polymerizes by head-to-tail interactions in an ionic strength-dependent manner. We produced a recombinant full-length chicken alpha-tropomyosin containing a 5-hydroxytryptophan residue at position 269 (formerly an alanine), 15 residues from the C terminus, and show that its fluorescence intensity specifically reports tropomyosin head-to-tail interactions. We used this property to quantitatively study the monomer-polymer equilibrium in tropomyosin and to calculate the equilibrium constant of the head-to-tail interaction as a function of ionic strength. Our results show that the affinity constant changes by almost 2 orders of magnitude over an ionic strength range of 50 mm (between I = 0.045 and 0.095). We were also able to calculate the average polymer length as a function of concentration and ionic strength, which is an important parameter in the interpretation of binding isotherms of tropomyosin with other thin filament proteins such as actin and troponin.
In male Wistar rats fed a diet enriched in polyunsaturated fatty acids and starch (PUFA+S), the percentage of muricidal (Mu) rats increased to 82% within 60 days. Mu rats had higher serum triglyceride levels and lower cholesterol levels than non-Mu rats. Water intake decreased in all rats on the PUFA+S diet concurrently with the increase in the proportion of Mu rats; protracted water restriction in rats fed standard diet also increased the percentage of Mu rats. In the offspring of two Wistar females fed the PUFA+S diet, the proportion of young Mu rats was 67%. When the PUFA+S diet was replaced with standard diet, the induced Mu behavior was not reversed. PK11195 (6 mg/kg i.p.), clonazepam (0.2 mg/kg i.p.), and flumazenil (15 mg/kg i.p.) were ineffective in reversing the induced Mu behavior, whereas 4'-chlorodiazepam (5 mg/kg i.p.) or muscimol (0.5 mg/kg i.p.) caused reversals of 63% or 50%, respectively. A 5-hydroxytryptophan overload (60 mg/kg i.p.) also reversed Mu behavior by 71%. All reversal effects were temporary. Pretreatment with yeast for 7 days before the PUFA+S diet was given prevented induction for more than 90 days on the PUFA+S diet, while similar pretreatment 4'Cl-diazepam resulted in 71% prevention of induction. The results are analyzed in terms of the involvement of endozepin, vasopressin, and serotonin receptors, and of possible genetic parameters.