Table 2. Cross-correlation of mRNA expression and PET measures of specific binding.

Receptor system	mRNA expression vs. PET-specific binding cross-correlation (ρ2)
	min	max	Mean	s.d.
Delta-opioid receptor mRNA and [11C]DPN VT
Probe 1	0.000	0.116	0.028	0.034
Probe 2	0.000	0.339	0.053	0.082
Kappa-opioid receptor mRNA and [11C]DPN VT
Probe 1	0.102	0.626	0.355	0.122
Probe 2	0.302	0.783	0.513	0.121
Probe 3	0.000	0.379	0.108	0.110
Mu-opioid receptor mRNA and [11C]DPN VT
Probe 1	0.005	0.339	0.090	0.086
Probe 2	0.010	0.245	0.110	0.058
Probe 3	0.000	0.223	0.054	0.064
5-HT1A receptor mRNA and [11C]WAY VT
Probe 1	0.679	0.991	0.882	0.055
Probe 2	0.158	0.784	0.565	0.197
Probe 3	0.658	0.965	0.858	0.064
5-HT1A receptor mRNA and [11C]CUMI BP
Probe 1	0.236	0.623	0.446	0.101
Probe 2	0.096	0.746	0.392	0.157
Probe 3	0.227	0.595	0.433	0.092

PET, positron emission tomography; [11C]DPN, [11C]diprenorphine; BP, binding potential; V_T, total distribution volume.