Differential response of TRHergic neurons of the hypothalamic paraventricular nucleus (PVN) in female animals submitted to food-restriction or dehydration-induced anorexia and cold exposure.
TRH neurons of the hypothalamic paraventricular nucleus (PVN), regulate pituitary-thyroid axis (HPT). Fasting activates expression of orexigenic peptides from the arcuate nucleus, increases corticosterone while reduces leptin, and pro-TRH mRNA levels despite low serum thyroid hormone concentration (tertiary hypothyroidism). TRH synthesis is positively regulated by anorexigenic peptides whose expression is reduced in fasting. The model of dehydration-induced anorexia (DIA) leads to decreased voluntary food intake but peptide expression in the arcuate is similar to forced-food restriction (FFR), where animals remain hungered. We compared the response of HPT axis of female Wistar rats submitted to DIA (2.5% saline solution, food ad libitum, 7 days) with FFR (provided with the amount of food ingested by DIA) and naïve (N) group fed ad libitum, as well as their response to acute cold exposure. Pro-TRH and pro-CRH mRNA levels in the PVN were measured by RT-PCR, TRH content, serum concentration of TSH and thyroid hormones by radioimmunoassay. DIA rats reduced 80% their food consumption compared to N, decreased PVN pro-CRH expression, serum estradiol and leptin levels, increased corticosterone similar to FFR. HPT axis of DIA animals failed to adapt: FFR presented tertiary hypothyroidism and DIA, primary. Response to cold stimulation leading to increased pro-TRH mRNA levels and TRH release was preserved under reduced energy availability in FFR rats but not in DIA, although the dynamics of hormonal release differed: TSH release augmented only in naïve; thyroxine in all but highest in DIA, and triiodothyronine in FFR and DIA suggesting a differential regulation of deiodinases.
Jaimes-Hoy
Lorraine
L
División de Investigaciones en Neurociencias, Instituto Nacional de Psiquiatría RFM, México D.F., México.
Joseph-Bravo
Patricia
P
de Gortari
Patricia
P
D000222:Adaptation, Physiological; D000626:Aminopeptidases / Q000378:metabolism; D000818:Animals; D000855:Anorexia / Q000209:etiology / Q000378:metabolism; D001007:Anxiety / Q000150:complications / Q000378:metabolism; D001069:Appetite Regulation / Q000502:physiology*; D001823:Body Composition; D003080:Cold Temperature; D003345:Corticosterone / Q000097:blood; D003681:Dehydration / Q000150:complications / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D005508:Food Deprivation / Q000502:physiology*; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism; D016555:Matched-Pair Analysis; D009474:Neurons / Q000378:metabolism*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D018025:Receptors, Thyrotropin-Releasing Hormone / Q000235:genetics / Q000378:metabolism; D012737:Sex Factors; D013312:Stress, Physiological / Q000150:complications / Q000378:metabolism; D013961:Thyroid Gland / Q000378:metabolism; D013963:Thyroid Hormones / Q000097:blood; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*
D011498:Protein Precursors; D012333:RNA, Messenger; D018025:Receptors, Thyrotropin-Releasing Hormone; D013963:Thyroid Hormones; D013973:Thyrotropin-Releasing Hormone; D000626:Aminopeptidases; C023166:pyroglutamyl-peptidase II; D011761:Pyrrolidonecarboxylic Acid; D003345:Corticosterone