The paraventricular nucleus (PVN) and the ventral tegmental area (VTA) have been shown to be involved in opioid mediated feeding behavior. The present study examined whether μ-opioid signalling between the PVN and VTA affected feeding behavior. Male Sprague-Dawley rats were cannulated with one cannula placed in the PVN and two cannulae placed in the VTA, which allowed for co-administration of the μ-opioid receptor agonist [D-Ala2, NMe-Phe4, Gly-ol5]-enkephalin (DAMGO) in one site and the opioid antagonist naltrexone (NTX) in the other site. Bilateral administration of DAMGO (1.2, 2.4 and 4.9 nmol) into the VTA stimulated feeding dose dependently at 2.4 and 4.9 nmol (P<0.05). The DAMGO (2.4 nmol)-induced increase of food intake following injection into the PVN was blocked by bilateral injection of NTX (6.6, 13.2 and 26.5 nmol) into the VTA at 2 and 4 h (P<0.05). In the reverse situation, the DAMGO (2.4 nmol)-induced increase of food intake following injection into the VTA was blocked by injection of NTX (13.2 and 26.5 nmol) into the PVN at 2 and 4 h (P<0.05). The present study suggests that a bidirectional μ-opioid-opioid signalling pathway exists between the PVN and the VTA which influences feeding.
Bibliographical noteFunding Information:
The authors would like to thank Sinead Eccles, Katrina Sharkey and Sarah Strange for their assistance. This research was supported by the Wellcome Trust 063938/GM/KM/RL.
- Paraventricular nucleus