Antinociceptive response to NT or to morphine in rats treated i.p. with saline, antisense PNA to the NTR1 (AS-NTR1), mismatch AS-NTR1 PNA, or antisense PNA to the MOR (AS-MOR1) or sense-NTR1 PNA microinjected into the PAG. PNA-treated animals received AS-NTR1, mismatch AS-NTR1, or AS-MOR1 10 mg/kg i.p., or sense-NTR1 PNA 5 μg microinjected into the PAG. Testing was 24 hr postinjection. For the these responses, animals either were placed on a hot plate after NT was microinjected into their PAG (18 nmol) or their tails were immersed in heated oil (tail flick assay) after they were treated with morphine (5 mg/kg i.p.). Data are reported as %MPE ± SEM as determined 30 min after drug (NT or morphine) delivery. The description before the slash at the bottom of each bar indicates pretreatment, while the drug listed after the slash indicates the drug used for testing. ∗, P < 0.001 vs. NT alone; †, P = 0.002 vs. NT alone.