Hypericum possesses a unique pharmacology in that it displays the pharmacology of many classes of antidepressants and new mechanisms not typical of standard antidepressants. The most potent of all its action is the moderate to high potency for inhibition of the reuptake of monoamines, serotonin, dopamine and noradrenaline and the amino-acid neurotransmitters GABA and glutamate. Unlike standard reuptake inhibitors, hypericum exerts this reuptake inhibition non-competitively by enhancing intracellular Na+ ion concentrations. At a receptor level, chronic treatment with hypericum downregulates beta1-adrenoceptor, upregulates post-synaptic 5-HT1A receptors and 5-HT2 receptors. Although the major constituent responsible for the antidepressant effect is thought to be hyperforin, other constituents such as hypericin, pseudohypericin, flavonoids and oligomeric procyanidines may also play a direct or indirect role. While reuptake inhibition may more than likely be responsible for most of the antidepressant effect, other mechanisms may also contribute alone or in combination to exert the overall antidepressant action.
The DSC is a synchronous system using characters composed from a ten-bit error detecting code . The bits are encoded using frequency shift keying . For High Frequency and Medium Frequency two tones 170 Hz apart either side of the allocated frequency with 100 Baud symbol rate are used. For VHF the two tones used are 1300 and 2100 Hz with a symbol rate of 1200 Baud . Each character is transmitted twice with a time delay. The detailed specification is published in the International Telecommunications Union recommendation ITU-R , revision 14 being the most recent.