PubMed · 6715671
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
M M Vilenchik, I N Polovinkin, A N Khokhlov. [Improved fluorometric method for DNA microanalysis].. https://pubmed.ncbi.nlm.nih.gov/6715671/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Following invasion of the human erythrocyte by the malaria parasite, Plasmodium falciparum, there appear in the parasitized cell new, high-capacity permeation pathways that transport a diverse range of low-molecular-mass solutes. In this study a series of 16 arylaminobenzoates, analogues of the Cl- channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), were tested for their effects on the transport of choline, a univalent cation, into malaria-infected cells. A number of the arylaminobenzoates were found to be potent inhibitors of malaria-induced choline transport and to be similarly effective at blocking the induced transport of the uncharged pyrimidine nucleoside thymidine and the univalent anion lactate. The data are consistent with the hypothesis that much of the induced transport of cations, anions and non-electrolytes into parasitized cells is via broad-specificity, anion-selective pathways of a single type. A comparison of the effects of the arylaminobenzoates on malaria-induced transport with their effects on a number of representative anion transport systems in normal mammalian cells suggests that it is possible to identify pharmacological agents that block the malaria-induced pathway while not significantly affecting important transport mechanisms in host tissues. The most potent of the induced-transport inhibitors identified were shown to inhibit [3H]hypoxanthine incorporation in in vitro parasite growth assays. These data support the view that the induced-transport pathway may be a viable pharmacological target.
The effects of selected local anesthetics on in vitro and in vivo measurements of dopamine transporter activity were determined to investigate the role of local anesthetic activity in the neuronal actions of cocaine. Cocaine inhibited [3H]2-beta-carbomethoxy-3-beta-(4-fluorophenyl)tropane 1.5-naphthalenedisulfonate (CFT) binding and [3H]dopamine uptake with estimated Ki and IC50 values of 0.6 microM and 0.7 micorM, respectively. Of the local anesthetics tested, only dimethocaine showed full displacement of CFT binding (0-30 microM tested) and full inhibition of dopamine uptake (0-100 microM tested). Dimethocaine was only slightly less potent than cocaine with an estimated Ki of 1.4 micorM and an IC50 value of 1.2 microM for [3H]CFT binding and dopamine uptake. At a maximum concentration of 100 microM, the ester containing local anesthetics procaine, tetracaine, piperocaine and the amide containing local anesthetic dibucaine and bupivacaine partially inhibited dopamine uptake by 47-70%. The ester containing local anesthetic propoxycaine and the amide containing local anesthetics prilocaine, etidocaine, procainamide, and lidocaine inhibited dopamine uptake by 8-30% at 100 microM. A 10 min administration of cocaine, dimethocaine, or procaine in the dialysis solution produced dose-dependent, reversible increases in endogenous dopamine efflux from the striata of awake rats. Cocaine and dimethocaine produced similar 12-fold increases in dialysate dopamine at concentrations of 0.1 mM and 1 mM respectively. Procaine (10 mM) produced a 6-fold increase in dialysate dopamine while lidocaine (1 mM) produced a reproducible and reversible decrease (30%). These results show that the cocaine-like actions of certain local anesthetics such as dimethocaine and procaine result from their direct actions of dopamine uptake inhibitors.
A number of esteratic local anesthetics serve as positive reinforcers and produce cocaine-like discriminative stimulus effects in animals. It has been suggested that the affinity of these compounds for a site on the dopamine transporter, and not their local anesthetic actions, is responsible for these abuse-related behavioral effects. In the present study, three local anesthetics previously shown to be self-administered in animals were examined in squirrel monkeys trained to discriminate cocaine (0.3 mg/kg) from saline in a two-lever, food-reinforced procedure. Dimethocaine (0.1-3.0 mg/kg) fully and dose-dependently substituted for cocaine. Doses of dimethocaine (1.7 mg/kg) and cocaine (0.3 mg/kg) which produced full (> 80%) substitution for cocaine were administered in combination with the dopamine D1 receptor antagonist SCH 39166 ((-)-trans-6,7,7a,8,9,13b-hexahydro-3-chloro-2-hydroxy-N-methyl-5H -benzo [d]naphtho-(2,1-b)azepine) and the dopamine D2 receptor antagonist raclopride (both at 0.003-0.03 mg/kg). SCH 39166 fully blocked the cocaine-like discriminative stimulus effects of dimethocaine and cocaine, but raclopride produced only partial antagonism of cocaine-lever selection. In addition, there was some evidence that raclopride blocked cocaine-lever responding produced by a lower dose of dimethocaine. In substitution studies, neither procaine (1-10 mg/kg) nor chloroprocaine (1-30 mg/kg) produced cocaine-like effects. These results support a role for dopamine in the behavioral effects of some local anesthetics.