PT  - JOURNAL ARTICLE
AU  - Nadège Altier
AU  - Jane Stewart
TI  - Dopamine Receptor Antagonists in the Nucleus Accumbens Attenuate Analgesia Induced by Ventral Tegmental Area Substance P or Morphine and by Nucleus Accumbens Amphetamine
DP  - 1998 Apr 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 208--215
VI  - 285
IP  - 1
4099  - http://jpet.aspetjournals.org/content/285/1/208.short
4100  - http://jpet.aspetjournals.org/content/285/1/208.full
SO  - J Pharmacol Exp Ther1998 Apr 01; 285
AB  - In the present study, we examined the effects of dopamine (DA) receptor antagonists infused into the nucleus accumbens septi (NAS) on analgesia induced by intra-ventral tegmental area (VTA) infusions of the substance P (SP) analog, DiMe-C7 or morphine and intra-NAS infusions of amphetamine. Rats received intra-NAS infusions of either the mixed DA receptor antagonist flupenthixol (1.5 or 3.0 μg/0.5 μl/side; DiMe-C7 only), the DA D1/D5 receptor antagonist SCH 23390 (0.1 μg/0.5 μl/side; DiMe-C7 only) or the DA D2-type receptor antagonist raclopride (1.0, 3.0 or 5.0 μg/0.5 μl/side). Ten minutes later, rats received intra-VTA infusions of DiMe-C7 (3.0 μg/0.5 μl/side) or morphine (3.0 μg/0.5 μl/side) or intra-NAS infusions of amphetamine (2.5 μg/0.5 μl/side). Animals were then administered the formalin test for tonic pain. Intra-NAS raclopride prevented analgesia induced by intra-VTA DiMe-C7, intra-VTA morphine and intra-NAS amphetamine. Similarly, intra-NAS flupenthixol or SCH 23390 attenuated the analgesia induced by intra-VTA DiMe-C7. These findings suggest that tonic pain is inhibited, at least in part, by enhanced DA released from terminals of mesolimbic neurons. Furthermore, the evidence that SP and opioids in the VTA mediate stress-induced analgesia suggests that the pain-suppression system involving the activation of mesolimbic DA neurons is naturally triggered by exposure to stress, pain or both. The American Society for Pharmacology and Experimental Therapeutics