Innate differences in the expression of brain-derived neurotrophic factor in the regions within the extended amygdala between alcohol preferring and nonpreferring rats.
BACKGROUND
Animal lines such as alcohol-preferring (P) and nonpreferring (NP) rats appear to be suitable animal models to investigate the biological basis of alcohol-drinking behaviors. The extended amygdala serves as a neuroanatomical substrate for alcohol-drinking behaviors. Brain-derived neurotrophic factor (BDNF) in the amygdala has been implicated in alcohol-drinking behaviors; however, its expression in the extended amygdala of P and NP rats is unknown. Therefore, we examined the basal expression of BDNF in the extended amygdala of alcohol naive P and NP rats.


METHODS
We determined the basal mRNA and protein levels of BDNF by in situ RT-PCR and immuno-histochemical procedure, respectively, in the amygdaloid [central nucleus of amygdala (CeA), medial nucleus of amygdala (MeA), and basolateral amygdala (BLA)], nucleus accumbal (NAc shell and core), and bed nucleus of stria terminalis (BNST) [lateral BNST (lBNST), medial BNST (mBNST), and ventral BNST (vBNST)] brain structures of P and NP rats. In addition, we examined the localization of BDNF in neurons using double-immunofluorescence labeling of BDNF with neuron-specific nuclear protein (NeuN) and also determined the number of NeuN-positive neurons in the amygdaloid structures of P and NP rats.


RESULTS
The mRNA and protein levels of BDNF were found to be significantly lower in both the CeA and MeA, but not in the BLA, of P compared with NP rats. We also found that BDNF was expressed in neurons in the amygdaloid structures of P and NP rats. In addition, we found that the number of NeuN-positive neurons was similar in the amygdaloid structures of P and NP rats. Interestingly, the mRNA and protein levels of BDNF were also significantly lower in the lBNST, mBNST, and vBNST of P compared with NP rats. On the other hand, mRNA and protein levels of BDNF were similar in the NAc shell and core structures of P and NP rats.


CONCLUSIONS
P and NP rats are selectively bred for higher and lower alcohol preference, respectively; therefore it is possible that lower BDNF levels in the amygdaloid and BNST structures may be associated with the excessive alcohol-drinking behaviors of P rats.
Prakash
Anand
A
Department of Psychiatry, University of Illinois at Chicago, Jesse Brown VA Medical Center, Chicago, Illinois 60612, USA.
Zhang
Huaibo
H
Pandey
Subhash C
SC
D000428:Alcohol Drinking / Q000235:genetics*; D000437:Alcoholism / Q000235:genetics; D000679:Amygdala / Q000737:chemistry*; D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000032:analysis / Q000235:genetics*; D005455:Fluorescent Antibody Technique; D005518:Food Preferences; D015870:Gene Expression / Q000235:genetics*; D007150:Immunohistochemistry; D008297:Male; D009714:Nucleus Accumbens / Q000737:chemistry; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014018:Tissue Distribution / Q000235:genetics
D019208:Brain-Derived Neurotrophic Factor; D012333:RNA, Messenger