Pharmacological Evaluation of Antipsychotics and Parkinson's Therapies

HAL (Sigma-Aldrich, St. Louis, MO) was diluted with 0.05% dimethyl sulfoxide (DMSO; Dojindo Laboratories, Japan) in sterile saline (vehicle). The drug is a traditional antipsychotic agent used primarily to treat schizophrenia and other psychoses (Gomes et al. 2013 (link); Vaz et al. 2018 (link); Magno et al. 2015 (link); Bruni et al. 2016 (link)) by relieving the symptoms of delusions and hallucinations commonly associated with schizophrenia. Haloperidol competitively blocks post-synaptic dopamine D2 receptors, eliminating dopamine neurotransmission while partially inhibiting 5-hydroxy-tryptamine (5-HT₂) and α1-receptors. However, there is negligible activation of dopamine D1-receptors (Seibt et al. 2010 (link)).
CBD (Cayman Chemical, Ann Arbor, MI) was diluted with 0.05% methanol and sterile saline. CBD, one of the major compounds present in the marijuana (C. sativa) plant, has some medicinal properties; however, its mechanism is not well known (Andreza et al. 2016 (link); Jeong et al. 2019 (link)).
Ropinirole hydrochloride (ROP; KYOWA Pharmaceutical Industry Co., Ltd, Osaka, Japan) was diluted with 0.05% dimethyl sulfoxide (DMSO; Dojindo Laboratories, Kumamoto, Japan) and sterile saline. The drug is a novel non-ergoline dopamine agonist, has selective affinity for dopamine D2 receptors, and is indicated for the treatment of early and advanced Parkinson’s disease (Pahwa et al. 2004 (link)).