RESUMO
In this study we investigated the influence of electrolytic lesion or of opioid agonist injections into the lateral hypothalamus (LH) on the dipsogenic, natriuretic, kaliuretic, antidiuretic, pressor, and bradycardiac effects of cholinergic stimulation of the medial septal area (MSA) in rats. Sham- and LH-lesioned male Holtzman rats received a stainless steel cannula implanted into the LH. Other groups of rats had cannulas implanted simultaneously into the MSA and LH. Carbachol (2 nmol) injection into the MSA induced water intake, pressor, and bradycardic responses. LH lesion reduced all of these effects (1-3 and 15-18 days). Previous injection of synthetic opiate agonist, FK-33824 (100 ng), into the LH reduced the water intake, natriuresis, kaliuresis, and pressor responses induced by carbachol injected into the MSA. These data show that both electrolytic lesion or injection of an opiate agonist in the LH reduces the fluid-electrolyte and cardiovascular responses to cholinergic activation of the MSA. The involvement of LH with central excitatory and inhibitory mechanisms related to fluid-electrolytic and cardiovascular control is suggested.
Assuntos
Pressão Sanguínea , Encéfalo/fisiologia , Carbacol/farmacologia , Frequência Cardíaca , Região Hipotalâmica Lateral/fisiologia , Equilíbrio Hidroeletrolítico/fisiologia , Animais , Pressão Sanguínea/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , D-Ala(2),MePhe(4),Met(0)-ol-encefalina/farmacologia , Comportamento de Ingestão de Líquido/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Região Hipotalâmica Lateral/efeitos dos fármacos , Masculino , Potássio/urina , Ratos , Sódio/urina , Equilíbrio Hidroeletrolítico/efeitos dos fármacosRESUMO
The present study investigates the participation and interaction between cholinergic and opiate receptors of the medial septal area (MSA) in the regulation of Na+, K+ and water excretion, drinking and blood pressure regulation. Male Holtzman rats were implanted with stainless steel cannulae opening into the MSA. Na+, K+ and water excretion, water intake and blood pressure were measured after injection of carbachol (cholinergic agonist), FK-33824 (an opiate agonist) + carbachol or naloxone (an opiate antagonist) + carbachol into MSA. Carbachol (0.5 or 2.0 nmol) induced an increase in Na+ and K+ excretion, water intake and blood pressure and reduced the urinary volume. FK-33824 reduced the urinary volume and Na+ and K+ excretion. Previous injection of FK-33824 (100 ng) into the MSA blocked the increases in Na+ and K+ excretion, water intake and blood pressure induced by carbachol. Naloxone (10 micrograms) produced no changes in the effect of 2.0 nmol carbachol, but potentiated the natriuretic effect induced by 0.5 nmol dose of carbachol. These data show an inhibitory effect of opiate receptors on the changes in cardiovascular, fluid and electrolyte balance induced by cholinergic stimulation of the MSA in rats.
Assuntos
Pressão Sanguínea/efeitos dos fármacos , Encéfalo/fisiologia , Carbacol/farmacologia , D-Ala(2),MePhe(4),Met(0)-ol-encefalina/farmacologia , Diurese/efeitos dos fármacos , Comportamento de Ingestão de Líquido/efeitos dos fármacos , Naloxona/farmacologia , Natriurese/efeitos dos fármacos , Análise de Variância , Animais , Encéfalo/efeitos dos fármacos , Interações Medicamentosas , Frequência Cardíaca/efeitos dos fármacos , Masculino , Ratos , Valores de ReferênciaRESUMO
An inhibitory effect on water, sodium and potassium excretion occurs after both systemic and central injections of morphine, beta-endorphin and other opioid peptides. Some investigators claimed that antidiuretic hormone release could be a mechanism explaining opioid-induced oliguria. Injection into the subfornical organ of a synthetic Met-enkephalin analog (FK 33824) reduced urine outflow as well as renal Na+ and K+ excretion. Identical effects were observed in hypophysectomized or in median eminence-lesioned rats. In addition, no changes were seen in blood pressure after FK 33824 injection into the subfornical organ. These results suggest that opioid stimulation of this structure induces an inhibitory effect on renal water, Na+ and K+ excretion, and that antidiuretic hormone release is probably not important to these phenomena.
Assuntos
Endorfinas/fisiologia , Rim/inervação , Hipófise/fisiologia , Receptores Opioides/fisiologia , Órgão Subfornical/fisiologia , Equilíbrio Hidroeletrolítico/fisiologia , Animais , D-Ala(2),MePhe(4),Met(0)-ol-encefalina/farmacologia , Masculino , Eminência Mediana/efeitos dos fármacos , Eminência Mediana/fisiologia , Hipófise/efeitos dos fármacos , Ratos , Ratos Endogâmicos , Receptores Opioides/efeitos dos fármacos , Órgão Subfornical/efeitos dos fármacos , Vasopressinas/fisiologia , Equilíbrio Hidroeletrolítico/efeitos dos fármacosRESUMO
The present study was performed to evaluate the participation of the subfornical organ (SFO) in the opioid modulation of urinary volume (Uv), and of sodium and potassium excretion. Intact and hypophysectomized (HYPOX) adult male rats were implanted with a cannula into the SFO, and injected with the opiate agonist FK 33-824 (FK). FK induced a significant decrease in Uv and in Na+ and K+ excretion in both intact and HYPOX rats. The data show that opioids play an important role in the regulation of hydromineral metabolism by the SFO
Assuntos
Ratos , Animais , Masculino , D-Ala(2),MePhe(4),Met(0)-ol-encefalina/farmacologia , Diurese/efeitos dos fármacos , Potássio/urina , Sódio/urina , Órgão Subfornical/fisiologia , Hipofisectomia , Ratos EndogâmicosRESUMO
1. The participation of the central histaminergic system in basal and opioid-induced prolactin secretion in male rats was investigated. 2. Central injections of cimetidine, an H2 antihistaminic, reduced basal plasma prolactin levels from 5.08 +/- 0.76 to 3.11 +/- 0.50 ng/ml (N = 10) while diphenhydramine, an H1 antihistaminic, had no effect. 3. Intracerebroventricular injections of FK 33824, a synthetic opioid peptide, produced a dose-dependent increase of prolactin secretion. This effect was partially blocked (-50%) by pretreatment with 20 ng diphenhydramine 15 min before administration of the opioid peptide. Cimetidine pretreatment failed to modify the prolactin rise in this case. 4. We conclude that brain histaminergic pathways exert a stimulatory tone on basal prolactin secretion which is mediated by H2 receptors and that the opioid-induced prolactin rise depends at least in part on activation of H1-histamine receptors.
Assuntos
Cimetidina/farmacologia , D-Ala(2),MePhe(4),Met(0)-ol-encefalina/farmacologia , Difenidramina/farmacologia , Prolactina/metabolismo , Receptores Histamínicos/efeitos dos fármacos , Animais , Cimetidina/administração & dosagem , D-Ala(2),MePhe(4),Met(0)-ol-encefalina/administração & dosagem , Difenidramina/administração & dosagem , Relação Dose-Resposta a Droga , Injeções Intraventriculares , Masculino , Ratos , Ratos EndogâmicosRESUMO
1. The possible role of central beta-2 adrenoceptors and epinephrine pathways in opioid-induced prolactin (PRL) rise was investigated. 2. FK 33824, a synthetic opioid peptide injected into the third ventricle of Wistar male rats, generated a PRL rise that was significantly reduced by pretreatment with IPS 339, a potent and selective beta-2 antagonist. 3. Inhibition of central epinephrine synthesis with SKF 64 139, which selectively blocks phenylethanolamine-N-methyltransferase, partially decreased the PRL release induced by FK 33824. 4. Practolol, a selective beta-1 adrenoceptor blocker, did not modify the PRL secretion induced by FK 33824. 5. The results indicate that this FK 33824-induced PRL rise depends in part on the functional integrity of central beta-2 adrenoceptors and that epinephrine pathways in the brain may play an important role in the mechanisms by which opioid peptides increase PRL secretion.
Assuntos
D-Ala(2),MePhe(4),Met(0)-ol-encefalina/farmacologia , Epinefrina/biossíntese , Isoquinolinas/farmacologia , Prolactina/sangue , Propanolaminas/fisiologia , Tetra-Hidroisoquinolinas , Animais , Masculino , Feniletanolamina N-Metiltransferase/antagonistas & inibidores , Ratos , Ratos EndogâmicosRESUMO
The present study was performed to evaluate the participation of the subfornical organ (SFO) in the opioid modulation of urinary volume (Uv), and of sodium and potassium excretion. Intact and hypophysectomized (HYPOX) adult male rats were implanted with a cannula into the SFO, and injected with the opiate agonist FK 33-824 (FK). FK induced a significant decrease in Uv and in Na+ and K+ excretion in both intact and HYPOX rats. The data show that opioids play an important role in the regulation of hydromineral metabolism by the SFO.