Anesthetic drugs specific agents

Contrast-enhanced MRI with Gd-DTPA has been applied to the evaluation of several compounds in man, some focusing on the hemodynamic effects of the drugs on cerebral blood volumes. Kolbtisch and others compared the anesthetic agents nitrous oxide and sevofhirane, noting them to produce compound-specific patterns of diffuse increases in cerebral blood volume (Kolbitsch et al., 2001). Intravenous cocaine, on the other hand, was observed to produce dose-dependent vasoconstriction of cerebral blood vessels (Kaufman et ul., 1998). 

First, it is clear that nearly all drugs with CNS effects act on specific receptors that modulate synaptic transmission. A very few agents such as general anesthetics and alcohol may have nonspecific actions on membranes (although these exceptions are not fully accepted), but even these non-receptor-mediated actions result in demonstrable alterations in synaptic transmission. 

The physiologic state induced by general anesthetics typically includes analgesia, amnesia, loss of consciousness, inhibition of sensory and autonomic reflexes, and skeletal muscle relaxation. The extent to which any individual anesthetic agent can produce these effects depends on the specific drug, the dosage, and the clinical situation. 

The method of drug administration or exposure to a poison may impart selectivity to a xenbiotic. For example, atropine can be applied directly to the eye for the dilation of the pupils. Note that eventual absorption into the blood stream from this site will cause systemic effects. Another example would be the topical (skin) application of a local anesthetic such as benzocaine. Monoclonal antibodies, which are specific for chemical functional groups, are tissue and cell-specific natural agents to which drugs can be chemically bonded. 

Hence, it is believed that general anesthetics exert most, if not all, of their effects by binding to one or more neuronal receptors in the CNS. This idea is a departure from the general perturbation theory described earlier that is, that the inhaled anesthetics affected the lipid bilayer rather than a specific protein. Continued research will continue to clarify the mechanism of these drugs, and future studies may lead to more agents that produce selective anesthetic effects by acting at specific receptor sites in the brain and spinal cord. 

---