Toxicology Essay Example | Topics and Well Written Essays - 1000 words - 1

Toxicology - Essay Example This paper declares that pleasure can be described as a â€Å"state or feeling of happiness and satisfaction resulting from an experience that one enjoys.†. Pleasure can serve to promote addiction. The process is a complex neurobiological one, which relies on the reward circuitry or limbic activity. These processes involve dopaminergic signalling. Endorphins and endogenous morphinergic mechanisms may also play a role. Addictive drugs are able to act directly on the reward pathways. Reward pathways are linked to the brain’s limbic system. The euphoria induced by drugs enhances the activity of the brain’s pleasure and reward systems. This discussion stresses that various species show differences in the rate of development of tolerance and physical dependence. Even in the same animal, tolerance develops to drugs at different rates, which rules out the possibility of an alteration in drug absorption, metabolism, excretion, etc., as a basis for the tolerance. Although tolerance develops to many of the effects of the opiates, miosis appears to be resistant to tolerance development. The pupil may be always sensitive to opiates because of the existence of different types of opiate receptors whereas the drug receptors on the cells of different tissues become less sensitive to the drug at different rates. â€Å"The most important point is that tolerance and dependence develop to different effects of drugs at different rates†.