Baclofen into the lateral parabrachial nucleus induces hypertonic sodium chloride intake during cell dehydration

Behavioral and Brain Functions

Everton H Kimura²  Lisandra B De Oliveira³  José V Menani¹  João C Callera² 

[1] Department of Physiology and Pathology, School of Dentistry, UNESP, Araraquara, São Paulo, Brazil

[2] Department of Basic Sciences, School of Dentistry, UNESP – Univ. Estadual Paulista, Rodovia Marechal Rondom, km 527, Araçatuba, São Paulo, 16018-805, Brazil

[3] Department of Biological Sciences, DECBI-NUPEB, Federal University of Ouro Preto, UFOP, Ouro Preto, Minas Gerais, Brazil

关键词: Lateral parabrachial nucleus;    Thirst;    Sodium appetite;    Dehydration;    Baclofen;   

Others  :  793512
DOI  :  10.1186/1744-9081-9-17

 received in 2012-12-07, accepted in 2013-04-23,  发布年份 2013

【 摘 要 】

Background

Activation of GABA_B receptors with baclofen into the lateral parabrachial nucleus (LPBN) induces ingestion of water and 0.3 M NaCl in fluid replete rats. However, up to now, no study has investigated the effects of baclofen injected alone or combined with GABA_B receptor antagonist into the LPBN on water and 0.3 M NaCl intake in rats with increased plasma osmolarity (rats treated with an intragastric load of 2 M NaCl). Male Wistar rats with stainless steel cannulas implanted bilaterally into the LPBN were used.

Results

In fluid replete rats, baclofen (0.5 nmol/0.2 μl), bilaterally injected into the LPBN, induced ingestion of 0.3 M NaCl (14.3 ± 4.1 vs. saline: 0.2 ± 0.2 ml/210 min) and water (7.1 ± 2.9 vs. saline: 0.6 ± 0.5 ml/210 min). In cell-dehydrated rats, bilateral injections of baclofen (0.5 and 1.0 nmol/0.2 μl) into the LPBN induced an increase of 0.3 M NaCl intake (15.6 ± 5.7 and 21.5 ± 3.5 ml/210 min, respectively, vs. saline: 1.7 ± 0.8 ml/210 min) and an early inhibition of water intake (3.5 ± 1.4 and 6.7 ± 2.1 ml/150 min, respectively, vs. saline: 9.2 ± 1.4 ml/150 min). The pretreatment of the LPBN with 2-hydroxysaclofen (GABA_B antagonist, 5 nmol/0.2 μl) potentiated the effect of baclofen on 0.3 M NaCl intake in the first 90 min of test and did not modify the inhibition of water intake induced by baclofen in cell-dehydrated rats. Baclofen injected into the LPBN did not affect blood pressure and heart rate.

Conclusions

Thus, injection of baclofen into the LPBN in cell-dehydrated rats induced ingestion of 0.3 M NaCl and inhibition of water intake, suggesting that even in a hyperosmotic situation, the blockade of LPBN inhibitory mechanisms with baclofen is enough to drive rats to drink hypertonic NaCl, an effect independent of changes in blood pressure.

【 授权许可】

   
2013 Kimura et al.; licensee BioMed Central Ltd.

【 图 表 】

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