TABLE 1

	'D 1 -like'		'D 2 -like'
	D 1	D 5	D 2(short)/(long)	D 3	D 4
Amino acids	446(h, r)	477(h)	414/443(h)	400(h)	387(h, r)
		475(r)	415/444(r)	446(r)
Antagonists	SCH 23390	?	Spiperone	Spiperone	Spiperone
			Raclopride	Raclopride	Raclopride
			Clozapine	Clozapine	Clozapine
			S33084	L745870	S33084
Homology
With D1 receptor	100	82	44	44	42
With D2(short)	44	49	100	76	54
Receptor localization	Caudate/putamen, nucleus accumbens, olfactory tubercle, hypothalamus, thalamus, frontal cortex	Hippocampus, thalamus, lateral mamillary nucleus, striatum, cerebral cortex (all low)	Caudate/putamen, nucleus accumbens, olfactory tubercle, cerebral cortex (low)	Nucleus accumbens, olfactory tubercle, islands of Calleja, cerebral cortex (low)	Frontal cortex, midbrain, amygdala, hippocampus, hypothalamus, medulla (all low), retina
Response	Adenylyl cyclase	Adenylyl cyclase	Adenylyl cyclase	Adenylyl cyclase	Adenylyl cyclase

 This classification is based on the IUPHAR Compendium of Receptor Characterization and Classification. Complete details are available in Alexander et al. (2004). Differences between the human and rat forms of the receptors are indicated by (h) and (r), respectively. The D₂ receptor exists in short and long variant spliced forms; these forms have similar, but not identical, pharmacology. This table has been adapted from one originally produced by Philip Strange.