The drug is also an agonist of the serotonin5-HT2A, 5-HT2B, and 5-HT2C receptors. Its EC50 values are 466nM at the serotonin 5-HT2A receptor, 40nM at the serotonin 5-HT2B receptor, and 2.3nM at the serotonin 5-HT2C receptor. It is a full agonist of the serotonin 5-HT2A and 5-HT2B receptors and a weak partial agonist of the serotonin 5-HT2C receptor (EmaxTooltip maximal efficacy = 20%).
Notes: The smaller the value, the more strongly the drug releases the neurotransmitter. The assays were done in rat brain synaptosomes and human potencies may be different. See also Monoamine releasing agent § Activity profiles for a larger table with more compounds. Footnotes:aENAPTooltip Ethylnaphthylaminopropane is a partial releaser of serotonin (EmaxTooltip maximal efficacy = 66%) and dopamine (Emax = 78%). Refs:
Effects
In animal studies, naphthylaminopropane was shown to reduce cocaineself-administration, yet produced relatively weak stimulant effects when administered alone, being a much less effective stimulant than dextroamphetamine. Further research was being conducted in primates to see if the drug would be a useful substitute for treating drug addiction in humans.
An important observation is that in behavioral studies, rodents would consistently self-administerselectivenorepinephrine–dopamine releasing agents (NDRAs) like dextroamphetamine, yet compounds that also potently release serotonin like naphthylaminopropane would not be self-administered. In addition to the drug's effects on self-administration, the available evidence suggests that the locomotor activation caused by dopamine releasers is also dampened when they additionally induce serotonin release. Notably, despite potent dopamine release induction, naphthylaminopropane produces weak or no locomotor activation in rodents.
The high affinity of naphthylaminopropane for the serotonin 5-HT2C receptor meant that it might function as an appetite suppressant and was being considered for possible clinical use for this indication (i.e., weight loss). However, concerns were raised over the affinity of the drug for the serotonin 5-HT2B receptor, since some of the more serious side effects of the serotonin-releasing weight loss drugfenfluramine were linked to activation of this receptor. It is uncertain, although was considered unlikely per the researchers who developed the drug, that activation of the serotonin 5-HT2A and 5-HT2B receptors occurs to a significant degree in vivo.
Chemistry
Naphthylaminopropane was first described in the scientific literature by 1939. The drug is also known as 2-naphthylaminopropane (2-NAP) or β-naphthylaminopropane, and it was described along with its positional isomer1-naphthylaminopropane (1-NAP; α-naphthylaminopropane). Both 2-NAP and 1-NAP failed to substitute for dextroamphetamine in rodent drug discrimination tests, suggesting that they lack psychostimulant-like effects. The β-keto and N-methyl analogue of 2-NAP has been assessed and was found to act as a potent SNDRA similarly to naphthylaminopropane.
A few derivatives of naphthylaminopropane have been developed or have appeared, including methamnetamine (N-methylnaphthylaminopropane; MNAP; PAL-1046), N-ethylnaphthylaminopropane (ENAP; PAL-1045), and BMAPN (βk-methamnetamine; β-keto-MNAP; 2-naphthylmethcathinone). Like naphthylaminopropane, these derivatives also act as potent monoamine releasing agents, including of serotonin, norepinephrine, and/or dopamine.
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