RESUMO
Thyrotropin-releasing hormone (TRH) plays an important role in central cardiovascular regulation. Recently, we described that the TRH precursor gene overexpression induces hypertension in the normal rat. In addition, we published that spontaneously hypertensive rats (SHR) have central extrahypothalamic TRH hyperactivity with increased TRH synthesis and release and an elevated TRH receptor number. In the present study, we report that intracerebroventricular antisense (AS) treatment with a phosphorothioate oligonucleotide against the TRH precursor gene significantly diminished up to 72 hours and in a dose-dependent manner the increased diencephalic TRH content, whereas normalized systolic blood pressure (SABP) was present in the SHR compared with Wistar-Kyoto (WKY) rats. Although basal thyrotropin was higher in SHR compared with WKY rats and this difference disappeared after antisense treatment, no differences were observed in plasma T4 or T3 between strains with or without AS treatment, indicating that the effect of the AS on SABP was independent of the thyroid status. Because the encephalic renin-angiotensin system seems to be crucial in the development and/or maintenance of hypertension in SHR, we investigated the effect of antisense inhibition of TRH on that system and found that TRH antisense treatment significantly diminished the elevated diencephalic angiotensin II (Ang II) content in the SHR without any effect in control animals, suggesting that the Ang II system is involved in the TRH cardiovascular effects. To summarize, the central TRH system seems to be involved in the etiopathogenesis of hypertension in this model of essential hypertension.
Assuntos
DNA Antissenso/farmacologia , Hipertensão/etiologia , Hormônio Liberador de Tireotropina/fisiologia , Angiotensina II/metabolismo , Animais , Pressão Sanguínea , Ventrículos Cerebrais/metabolismo , DNA Antissenso/administração & dosagem , Modelos Animais de Doenças , Hipertensão/genética , Hipertensão/metabolismo , Masculino , Oligonucleotídeos Antissenso/administração & dosagem , Oligonucleotídeos Antissenso/farmacologia , Radioimunoensaio , Ratos , Ratos Endogâmicos SHR , Ratos Endogâmicos WKY , Sistema Renina-Angiotensina/fisiologia , Hormônios Tireóideos/sangue , Hormônio Liberador de Tireotropina/análise , Hormônio Liberador de Tireotropina/biossíntese , Hormônio Liberador de Tireotropina/genéticaRESUMO
The ontogeny of the thyrotropin releasing hormone (TRH) neuronal system was evaluated by immunocytochemistry in Bufo arenarum. The first appearance of TRH immunoreactive fibers was at early premetamorphosis. These fibers were found in small numbers and weakly stained in the median eminence and pars nervosa. With the advance of larval development, TRH-like material stained intensely and tended to aggregate in the median eminence, pars nervosa and pars intermedia. At climax stages immunoreactive fibers and perikarya (weakly stained) were also identified in the preoptic area. In adult specimens TRH perikarya and neuronal fibers were found in the preoptic and infundibular nuclei of the hypothalamus and in the amygdala, septum and diagonal band of Broca of the telencephalon. In addition, TRH neuronal fibers and endings were found in the preoptic-hypophyseal tract, the external zone of the median eminence, the pars nervosa and pars intermedia. Fibers were absent in the pars distalis. This study represents the first immunocytochemical demonstration of TRH in Bufo species, and serves as a basis for clarification of the neuroendocrine regulation of metamorphosis.
Assuntos
Química Encefálica/fisiologia , Encéfalo/crescimento & desenvolvimento , Bufo arenarum/crescimento & desenvolvimento , Hipófise/química , Hipófise/crescimento & desenvolvimento , Hormônio Liberador de Tireotropina/análise , Fatores Etários , Animais , Anticorpos , Encéfalo/citologia , Feminino , Masculino , Neurônios/química , Hipófise/citologia , Hormônio Liberador de Tireotropina/imunologiaRESUMO
PURPOSE: Thyrotropin-releasing hormone (TRH), present in extra hypothalamic brain areas, has been proposed to have neuromodulatory functions and to be susceptible to change by electrical stimulation paradigms. We measured TRH concentrations of several brain areas during kindling development before its establishment and determined whether the changes detected in TRH levels were related to the behavioral stages of kindling, the number of stimulations required to reach these stages and, with the electrophysiological parameters characteristic of this paradigm (amygdaloid afterdischarge (AD) frequency, duration, and propagation). METHODS: Male Wistar rats were implanted stereotaxically with indwelling bipolar electrodes in the basolateral nucleus of the amygdala and with two stainless-steel electrodes epidurally in frontal cortex. Amygdaloid kindling was induced by daily electrical stimulation; AD frequency and duration were recorded and analyzed throughout the development of kindling. TRH was extracted from several regions and quantified by radioimmunoassay (RIA). RESULTS: Modifications in TRH concentrations were detected, depending on the region assayed, from stage II of kindling. A positive correlation was noted between the levels of TRH and the frequency and propagation of AD, but not with the number of stimulations. The rate of change in TRH concentration in relation to AD frequency or duration was highest in frontal cortex followed by hippocampus and amygdala. CONCLUSIONS: A graded response was noted in the increase in TRH concentration dependent on the increase of AD frequency and propagation. The rate of response correlated with the region's epileptogenic susceptibility.
Assuntos
Tonsila do Cerebelo/química , Química Encefálica , Eletroencefalografia , Epilepsia/metabolismo , Excitação Neurológica/metabolismo , Hormônio Liberador de Tireotropina/análise , Tonsila do Cerebelo/metabolismo , Tonsila do Cerebelo/fisiologia , Animais , Estimulação Elétrica , Eletrofisiologia , Epilepsia/fisiopatologia , Lobo Frontal/química , Lobo Frontal/fisiologia , Lateralidade Funcional/fisiologia , Hipocampo/química , Hipocampo/fisiologia , Excitação Neurológica/fisiologia , Masculino , Radioimunoensaio , Ratos , Ratos Wistar , Hormônio Liberador de Tireotropina/biossínteseRESUMO
Se desarrolló un método analítico para el control de la calidad y estudio de estabilidad de protirelina inyectable. Se realizó el análisis por cromatografía líquida de alta resolución con la utilización de un sistema isocrático de buffer fosfato-metanol (85:15) como fase móvil y una columna Lichrosorb RP-18 de 250 x 4 µm y detección ultravioleta, a una longitud de onda de 210 nm. El método analítico resultó ser lineal, preciso, exacto y específico en el rango de concentraciones estudiadas
Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Estabilidade de Medicamentos , Qualidade dos Medicamentos Homeopáticos , Hormônio Liberador de Tireotropina/análiseRESUMO
Thyrotropin-releasing hormone (TRH) plays an important role in central cardiovascular regulation through the activation of different neurotransmitter systems at distinct extrahypothalamic sites. To study possible alterations in the TRH system in the hypertensive state, we measured TRH concentration in cerebrospinal fluid and TRH content of the preoptic area in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) by radioimmunoassay. In addition, we also measured the density of the TRH receptor in this area by a rapid filtration technique using [3H]methyl-TRH. We found a significant increase in both the TRH content (634 +/- 61 versus 350 +/- 26 pg/mg protein, SHR versus WKY; P < .01, n = 5) and density of TRH receptors without changes in affinity (Bmax, 5.0 +/- 0.1 versus 3.3 +/- 0.1 fmol/mg protein, P < .01, n = 4). An increase in TRH concentration was also found in the cerebrospinal fluid of SHR (30 +/- 3 versus 21 +/- 2 pg/mL, P < .01, n = 5), suggesting increased TRH release in the central nervous system. Northern blot analysis indicated a threefold augmented abundance of TRH precursor mRNA in the preoptic area of SHR. A polyclonal antibody raised against TRH injected peripherally or intracerebroventricularly lowered arterial blood pressure in SHR but not in WKY. In addition, long-term treatment with enalapril (5 mg/kg twice daily), which was effective in inhibiting serum angiotensin-converting enzyme activity by more than 50%, decreased arterial blood pressure and preoptic area TRH content of SHR, whereas another vasodilator, diltiazem (10 mg/kg every 8 hours), failed to produce a similar change.(ABSTRACT TRUNCATED AT 250 WORDS)