Adrenergic receptors definition

Note that there are actually more than two beta adrenergic receptors. A beta-3 has been definitely identified and there may be a beta-4 as well. 

The answer is h. (Katzung, p 482.) Haloperidol, a butyrophenone, is by far the most likely antipsychotic to produce extrapyramidal toxicides. Other agents, such as piperazine (an aromatic phenothiazine), thiothixene (a thioxanthene), and pimozide (a diphenylbutyropiperidine) are comparitively less likely to produce extrapyramidal toxicity than haloperidol. The antagonism of dopamine in the nigrostriatal system might explain the Parkinson-like effects. Both haloperidol and pimozide act mainly on D2 receptors, whereas thioridazine and piperazine act on a-adrenergic receptors, and have a less potent but definite effect on D2 receptors. 

---