Many viruses encode proteins that can inhibit apoptosis. Tramadol does not inhibit the reuptake or induce the release of dopamine. They do not, however, inhibit or induce these enzymes. Other intracellular toxins do not directly inhibit protein synthesis. CAs inhibit indole-3-acetic acid oxidation and enhance ethylene biosynthesis. Fungi produce compounds that inhibit viruses and cancer cells. In this way, allosteric interactions can either inhibit or activate enzymes. Oral contraceptives inhibit ovulation and so prevent conception. It does not inhibit any CYP450 enzymes. This effect is caused by the ability of some progestins to inhibit androgen receptors. Tamoxifen may inhibit its own metabolism. The hope was to inhibit cell proliferation and promote cytotoxicity. Aspirin may also inhibit the absorption of vitamin C. Within these cells, some also inhibit specific pyramidal cell dendrites. Amantadine probably does not inhibit monoamine oxidase (MAO) enzyme.