Corticotropin-releasing factor type-2 receptor and corticotropin-releasing factor-binding protein coexist in rat ventral tegmental area nerve terminals originated in the lateral hypothalamic area

There is significant functional evidence showing that corticotropin‐releasing factor type‐2 receptor (CRF2R) and corticotropin‐releasing factor‐binding protein (CRF‐BP) regulate glutamatergic synapses onto ventral tegmental area (VTA) dopaminergic neurons. It has been shown that CRF requires CRF‐BP to potentiate N‐methyl‐d‐aspartate receptors in dopaminergic neurons through CRF2R, and that increases glutamate release in cocaine‐treated rats through the activation of CRF2R only by agonists with high affinity to CRF‐BP. Furthermore, this CRF‐mediated increase in VTA glutamate is responsible for stress‐induced relapse to cocaine‐seeking behaviour. However, there is a lack of anatomical evidence to explain the mechanisms of CRF actions in VTA. Thus, it was studied whether CRF2R and CRF‐BP are expressed in VTA nerve terminals, using a synaptosomal preparation devoid of postsynaptic elements. The current results show that both proteins are co‐expressed in glutamatergic and γ‐aminobutyric acid (GABA)ergic VTA synaptosomes. A main glutamatergic input to the VTA that has been associated to addictive behaviour is originated in the lateral hypothalamic area (LHA). Thus, this study was focused in the LHA–VTA input using orexin as a marker of this input. The results show that CRF2R and CRF‐BP mRNA and protein are expressed in the LHA, and that both proteins are present in orexin‐positive VTA synaptosomes. The results showing that CRF2R and CRF‐BP are expressed in the LHA–VTA input give anatomical support to suggest that this input plays a role in stress‐induced relapse to cocaine‐seeking behaviour. Corticotropin releasing factor type‐2 receptor (CRF2R) and CRF‐binding protein (CRF‐BP) mRNA and protein are expressed in ventral tegmental area (VTA) and lateral hypothalamic area (LHA). Both proteins co‐exist in glutamatergic and GABAergic, but not in cholinergic VTA nerve terminals. Furthermore, CRF2R and CRF‐BP are present in VTA orexin‐positive varicosities (varicosome) and nerve terminals (synaptosome) of glutamatergic/orexinergic LHA neurons.