Answer:
PCP and Ketamine (D)
Step-by-step explanation:
Depressants, or depressive drugs, are drugs that decrease the level of activity in the brain.
Ketamine and phencyclidine (PCP) are chemically similar drugs used for anesthesia. Ketamine is available in powder or liquid form. The powder may be smelled or taken orally. The fluid may be injected intravenously, into a muscle (intramuscularly) or under the skin (subcutaneously). Phencyclidine (PCP) is usually smoked but it can also be smelled or taken orally.
The neuropharmacology of both drugs are similar and complex, since they interacts with various types of receptors at various binding sites, including glutamate receptors, both NMDA (N-methyl-Daspartate) and non-NMDA; opiates; gabaergic; serotonergics; besides acting, directly or indirectly, on monoamines (acetylcholine, noradrenaline and dopamine. But they act inhibiting the excitatory receptors (NMDA), resulting in a depressive effect in CNS (central nervous system).
Benadryl (diphenhydramine) is used for the treatment of allergic reactions. It acts blocking the histamine 1 receptor (H1), resulting in a antihistamine effect and with anticholinergic side effects (such as dryness) and sedatives. This drug also has a depressive effect, but its effect is more related to pheriperal nervous system.