In situ hybridization analysis of preprotachykinin-A and -B mRNA levels in short-term sodium depletion.
Tachykinins inhibit salt appetite when applied intracranially in a number of brain regions and may function as endogenous inhibitors of sodium intake. To test the hypothesis that induced increases in salt appetite might involve disinhibition via a reduction in endogenous tachykinin expression, we used a semi-quantitative in situ hybridization analysis to investigate changes in brain areas expressing preprotachykinin-A (PPT-A) and preprotachykinin-B (PPT-B) mRNAs of rats after 1 day of sodium depletion (1d Na dep). PPT-A mRNA levels were detected in neurons of the olfactory tubercle (Tu), the nucleus of the olfactory tubercle (LOT), the dorsal and ventral caudate-putamen (d-CPu and v-CPu), the bed nucleus of the stria terminalis (BNST), the medial preoptic area (mPOA), the habenula (Hb) and the postero-dorsal part of the amygdala (MePD). PPT-B mRNA levels were measured in fundus striati (FStr), d-CPu, v-CPu, BNST, mPOA, dorsomedial hypothalamic nucleus (DMD), arcuate nucleus (Arc), central amygdaloid nucleus (CeL), basolateral amygdaloid nucleus (BLV), LOT, Hb and basal nucleus of Meynert (B). 1d Na dep reduced by 33-61% the mean number of PPT-A grains/cell in Tu, LOT, d-CPu, BNST, mPOA, Hb and MePD compared to control animals. Levels of PPT-B mRNA were not reduced as much by 1d Na dep, although statistically significant reductions of 26, 34 and 17% were found in v-CPu, BNST and B, respectively. These findings, therefore, support the hypothesis that endogenous tachykinins exert an inhibitory influence over sodium appetite.
Pompei
P
P
Department of Pharmacological Sciences and Experimental Medicine, University of Camerino, Italy. pompei@cambio.unicam.it
Lucas
L R
LR
Angeletti
S
S
Massi
M
M
McEwen
B S
BS
D000818:Animals; D001921:Brain / Q000378:metabolism*; D017403:In Situ Hybridization / Q000379:methods; D008297:Male; D009928:Organ Specificity; D011498:Protein Precursors / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000172:deficiency*; D015320:Tachykinins / Q000096:biosynthesis*; D014158:Transcription, Genetic
D011498:Protein Precursors; D012333:RNA, Messenger; D015320:Tachykinins; C044206:preprotachykinin; D012964:Sodium