Hypo- and Hyperthyroidism Affect Neuropeptide Acid-Glutamic-Isoleucine (NEI) Content in Discrete Brain Areas of Adult Male Rats.

AYALA C; VALDEZ SR; NAVARRA MORERO ML; SOAJE M; CARREÑO NB; BITTENCOURT JC; JAHN GA; CELIS ME

Florencia

Congreso; 8th IBRO World Congress of Neuroscience.; 2011

IBRO

Neuropeptide acid-glutamic-isoleucine (NEI) derived from pp-MCH, inhibits thyrotropin releasing hormone (TRH) release in mediobasal hypothalamus. To investigate the relationship between NEI and the hypothalamic-pituitary-thyroid (HPT) axis, we studied the effect of hypothyroidism (hypoT) and hyperthyroidism (hyperT) on NEI content in brain areas related to metabolism and reproduction, and whether such alterations are related to the time of day. Adult male Wistar rats were divided into control and treated: hypoT received PTU 0.1 g/l in drinking water during 7 and 24 days, hyperT received L-T4 250 μg/kg sc daily for 4 days. Animals were sacrificed in the morning (10.00-12.00 h) and afternoon (17.00-19.00 h). Trunk blood was collected; pineal gland, brain and posterior pituitary (PP) were obtained. Coronal brain slices of 1 mm were serially sectioned from 0.12 mm anterior to bregma to approximately −3.48 mm posterior to bregma according to Paxinos and Watson Atlas, Ed. 2007. The hypothalamic areas of interest were microdissected. NEI content was determined by radioimmunoassay (RIA). HypoT and hyperT were confirmed by determination of triiodothyronine, total thyroxine, and thyrotropin levels by RIA. Statistical analysis was performed using two-way ANOVA with Bonferroni post-test. In all areas, except in OVLT+AVPV, NEI contents was similar in the controls, hypoT-7 had a very small effect in NEI concentration but hypoT-24 induced NEI reductions in the morning and afternoon in PeFLH and PVH, only in the morning in OVLT+AVPV and ME+Arc, and in POA only in the afternoon. HyperT induced higher NEI concentrations in the POA in the morning and in the ME+Arc and Pi in the afternoon. Thyroid hormones have a differential regulation of NEI levels in several brain areas probably through regulation of its synthesis, release or degradation.