Milacemide, a prodrug for glycine, is an inhibitor of the B form of monoamine oxidase. This drug could enhance dopaminergic activity in the brain and could be used as therapy for Parkinson's disease. Milacemide participated in clinical trials as a treatment for senile dementia of the Alzheimer type (SDAT). However, results have shown the drug was not an effective treatment in enhancing cognition in SDAT patients. In addition, milacemide has been tested for antiepileptic efficacy; however, this study was discontinued.

PF-2545920 is an orally-active phosphodiesterase 10A (PDE10A) inhibitor originated by Pfizer, for the treatment of Huntington's disease. PF-2545920 was originally developed by Pfizer for the treatment of schizophrenia. But later clinical studies for Schizophrenia were discontinued. PF-2545920 is a potent and selective PDE10A inhibitor with IC50 of 0.37 nM, with >1000-fold selectivity over the PDE. PF-2545920 is active in a range of antipsychotic models, antagonizing apomorphine-induced climbing in mice, inhibiting conditioned avoidance responding in both rats and mice, and blocking N-methyl-D-aspartate antagonist-induced deficits in prepulse inhibition of acoustic startle response in rats, while improving baseline sensory gating in mice.

Metoprine is a diaminopyrimidine folate antagonist with potential antineoplastic activity. Metoprine inhibits dihydrofolate reductase, resulting in decreased cellular folate metabolism and cell growth. Metoprine shows potent in vitro antitumor activity against several experimental tumors including methotrexate-resistant tumors. Metoprine inhibits the enzyme dihydrofolate reductase, much less effectively than methotrexate but it also inhibits histamine-N-methyltransferase, resulting in decreased histamine catabolism. S phase cells are most sensitive, whilst cells in G2 and M are least sensitive to the lethal effects of Metoprine, and a prolonged exposure to a high Metoprine concentration produces maximum cytotoxic effects. After oral administration, Metoprine has a widespread distribution and concentration in all tissues examined with the highest tissue/plasma ratios found in brain, lung, pancreas, and skin. Phase I and early Phase II clinical trials in various centers have shown activity in hypernephroma, epidermoid carcinoma arising in bronchus or head and neck, central nervous system leukemia, malignant melanoma, and mycosis fungicides. Metoprine had been in some phase II clinical trials but further studies were discontinued due to CNS and hematological toxicity.

Spiromustine is a bifunctional nitrogen alkylating agent with antineoplastic activity and lipophilic properties. Preclinical screening has shown activity against a variety of tumors, including an intracranially implanted ependymoblastoma. Alkylating activity has been demonstrated in an intracerebral glioma in the rat. Spiromustine is a cell cycle non-specific agent. Animal pharmacology studies have shown a biphasic plasma decay curve, with hepatic metabolism and excretion, an enterohepatic circulation of metabolites, and approximately 50% renal excretion of unchanged drug. Toxicology studies in mice, rats, and dogs showed that dose-related myelosuppression and neurotoxicity predominated; other organ toxicities were mild. In Phase I clinical trials Neurotoxicity was the dose-limiting toxicity presenting as alterations in cortical integrative functions (orientation, language, coordination), leading to a decrease in the level of consciousness.

Psilocybin is a naturally occurring psychedelic prodrug compound produced by more than 200 species of mushrooms, collectively known as psilocybin mushrooms. Once ingested, psilocybin is rapidly metabolized to the psilocin, which then acts on serotonin receptors in the brain. Psilocybin was identified as the active hallucinogenic compound in magic mushrooms in 1959, but humans have used assorted psilocybin mushrooms in religious ceremonies since prehistoric times. In the 1960's psilocybin was marketed for use as a treatment for various psychoses, however, it was withdrawn from the market when the regulatory environment changed. Recently there has been as renewed interest in studying the medicinal uses of psilocybin for treatment of anxiety, depression, migraine headaches, addictions, and other neuropsychiatric conditions.

Idalopirdine (Lu AE58054) is a Serotonin 6 receptor (5-HT6) antagonist. Idalopirdine exrets good oral bioavailability and robust efficacy in a rat model of cognitive impairment in schizophrenia. In rats idalopirdine potentiates the effects of acetylcholinesterase inhibitor donepezil on two pharmacodynamic biomarkers associated with cognition, i.e. neuronal oscillations and extracellular ACh levels in the hippocampus. Such potentiation could contribute to the procognitive effects of idalopirdine observed in donepezil-treated Alzheimer's disease patients. The compound is being developed by Lundbeck as an adjunctive therapy with acetylcholinesterase inhibitor donepezil, and is in phase III development for the treatment of Alzheimer's disease in multiple countries worldwide. A phase II trial for the treatment of cognitive impairment associated with schizophrenia was conducted; however no recent reports of development for idalopirdine have been identified.

Chlorpyrifos (CPF) is a crystalline organophosphate insecticide. It was introduced in 1965 by Dow Chemical Company and is known by many trade names (see table), including Dursban and Lorsban. It acts on the nervous system of insects by inhibiting acetylcholinesterase. Chlorpyrifos is an organophosphate, with potential for both acute toxicity at larger amounts and neurological effects in fetuses and children even at very small amounts. For acute effects, the EPA classifies chlorpyrifos as Class II: moderately toxic. CPF is a strongly genotoxic agent that induces DNA damage and cell apoptosis.

KETAZOCINE, a benzomorphan derivative, is a kappa opioid receptor agonist. It is used in opioid receptor research.

Chloralose (alpha-Chloralose, 1,2-O-(2,2,2-Trichloroethylidene)-α-D-glucofuranose) is an avicide, and a rodenticide commonly used for the control of mice and birds. Since its initial description in 1893, alpha-chloralose has undergone extensive pharmacologic evaluation. It has been characterized as a compound possessing potent CNS activity and has been evaluated in humans and animal models for its therapeutic properties. Though the toxicity of the compound prohibits its use as a human therapeutic agent, it has been employed widely as an animal anesthetic in the laboratory setting. α-Chloralose is widely used as an anesthetic in studies of the cerebrovasculature because of its presumed minimal depression of autonomic function. α-Chloralose acts as the positive allosteric modulator of GABA-A receptor and increases the affinity for GABA 5-fold and produced a small increase in the efficacy of GABA. Studies of α-Chloralose interactions with other allosteric modulators determined that α-Chloralose binds to a site on the GABAA receptor complex distinct from the benzodiazepine, neurosteroid and barbiturate sites.

Cimoxatone is a fully reversible inhibitor selective for the A form of monoamine oxidase. Oral administration of Cimoxatone increased brain noradrenaline, dopamine, and serotonin and decreased DOPAC , 5-HIAA, and 3-methoxy-4-hydroxyphenylethylene glycol sulfate.