What exactly is substance tolerance?
How does it work?
Does the brain shutdown some receptors?
For example, why does the same dose today have a weaker effect if taken tomorrow?
Drug tolerance is a commonly encountered effect in pharmacology, it is a progressive diminution of the susceptibility of a human or animal to the effects of a drug, resulting from its continued administration., requiring an increase in concentration to achieve the desired effect. Tolerance is reversible, and its rate depends on the characteristics of each particular drug. Some drugs create tolerance more quickly than other. LSD develops tolerance to psychoactive effects very quickly (1-2 days), and cocaine or opiates in a week. There is also different rates of tolerance development for different effects of the same drug. For example, tolerance to anxiolytic effect of benzodiacepines develops in a few days but tolerance to anticonvulsivant effects develops in months.
The pharmacological mechanisms involved are complex. Sometimes depends on the ability of the organism to better metabolize and degrade the substance and other there is a decreased sensitivity of cerebral receptors.