RESUMEN
A new route for operating affinity biosensors based on the voltammetric monitoring of the accumulated guest (analyte) is described. High sensitivity and selectivity accrue from the coupling of the specific receptor binding process and the inherent sensitivity of the preconcentration/pulse-voltammetric scheme. The redox (measurement) process results in dissociation of the receptor-guest complex, thus allowing multiple analytical determinations. The receptor layer also serves as an effective barrier that excludes interfering species. The new concept of preconcentration/voltammetric affinity biosensors is illustrated in connection with the detection of phenothiazine drugs using Langmuir-Blodgett films of their receptor, the enzyme tyrosine hydroxylase. The effect of various experimental variables upon the sensor performance is described.
Asunto(s)
Técnicas Biosensibles , Fenotiazinas/análisis , Tirosina 3-Monooxigenasa/química , Oxidación-Reducción , Sensibilidad y EspecificidadAsunto(s)
Aminas Biogénicas/biosíntesis , Encéfalo/metabolismo , Psicotrópicos/farmacología , Animales , Antipsicóticos/farmacología , Encéfalo/efectos de los fármacos , Encéfalo/enzimología , Técnicas In Vitro , Cinética , Ratas , Sinapsis/metabolismo , Sinaptosomas/metabolismo , Tirosina 3-Monooxigenasa/metabolismoRESUMEN
Electrical stimulation of rat hypothalamic synaptosome suspensions produced activation of tyrosine hydroxylase due to increase of the affinity for tyrosine and 6,7-dimethyl-5,6,7,8-tetrahydropterine cofactor, decrease of the affinity for dopamine and enhancement of substrate inhibition. Cocaine (10(-7) - 10(-5) M) in vitro caused enzyme activation; when administered to animals systemically (0.5 mg/kg) the drug produced inhibition of hypothalamic tyrosine hydroxylase probably through a receptor-mediated feedback mechanism.
Asunto(s)
Encéfalo/enzimología , Tirosina 3-Monooxigenasa/metabolismo , Animales , Encéfalo/fisiología , Catecolaminas/biosíntesis , Cocaína/farmacología , Retroalimentación , Hipotálamo/enzimología , Hipotálamo/fisiología , Receptores de Neurotransmisores , Sinaptosomas/enzimología , Sinaptosomas/fisiologíaRESUMEN
The effect of a number of neuroleptics and tricyclic antidepressants on the activity of rat hypothalamic tyrosine hydroxylase was studied utilizing a direct spectrophotometric method. All the neuroleptics (but not the antidepressants) were able to reverse the substrate inhibition of the enzyme occurring when the tyrosine concentration in the medium was increased. Haloperidol, haloanisone and fluphenazine were found to activate the enzyme at optimal tyrosine concentrations in contrast to other neuroleptics which reduced the enzyme activity. The systemic administration of fluphenazine and clozapine was followed by an increase in the activity of striatal and hypothalamic tyrosine hydroxylase. The same drugs failed to produce this effect when administered chronically for 8 days.