George B Karkanias

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Hypothalamic circuits utilizing the monoamine neurotransmitter norepinephrine (NE) may be key elements upon which the ovarian steroids estradiol (E2) and progesterone (P) act to regulate female reproductive behavior. Recent studies have focused on the modulation of hypothalamic NE release by E2 and P treatments that facilitate sexual behavior. Brain(More)
We previously demonstrated that estradiol administered in vivo elevates the number of alpha 1-adrenoceptors in preoptic area (POA) and hypothalamic membranes from ovariectomized female rats and potentiates alpha 1 receptor augmentation of beta-adrenoceptor-stimulated cAMP formation in slices from these brain regions. Present studies examined (1) if(More)
Present experiments examined whether previously observed hormone-dependent differences in norepinephrine-stimulated cAMP accumulation in hypothalamic and preoptic area slices are attributable to differences in noradrenergic receptor number or binding affinity. When compared to ovariectomized controls, hypothalamic and preoptic area membranes from(More)
These studies determined whether deficits in reproductive behavior observed in streptozotocin (STZ)-induced diabetic female rats are caused by hyperglycemia or loss of insulin. Female Sprague-Dawley rats were ovariectomized and made diabetic by a single ip injection of STZ (75 mg/kg). Reproductive behavior was measured 12 days after the onset of(More)
This review focuses on findings from our laboratory regarding mechanisms by which the ovarian steroid hormones, estradiol (E2) and progesterone (P), act in the hypothalamus (HYP) to regulate the expression of lordosis, an important component of female reproductive behavior in rats and many other species. The first section summarizes recent work suggesting(More)
Estradiol treatment for 48 h increases the density of alpha 1B-adrenoceptors in the hypothalamus-preoptic area of ovariectomized female rats by five- to six-fold. Present studies tested the hypothesis that estradiol elevation of hypothalamus-preoptic area alpha 1B-adrenoceptor density is correlated with increased levels of mRNA for this receptor. We(More)
Diabetic female rats have decreased ovulation, sexual behavior, and luteinizing hormone (LH) surges. Peripheral insulin treatment restores the phenotype to normal. We administered central insulin and analyzed serum LH during the time of the LH surge in diabetic and non-diabetic animals to determine if central insulin was sufficient to normalize the(More)
These studies determined whether diabetes and estradiol treatment altered norepinephrine (NE) release from hypothalamus, preoptic area (POA), and cortical slices from ovariectomized (OVX) female rats. Animals were sacrificed 12 days after the onset of streptozotocin-induced diabetes and 48 h following vehicle or estradiol injection. Brain slices were(More)
We previously demonstrated that in vivo estradiol treatment markedly attenuates alpha 2-adrenoceptor function and coupling to G-proteins in the hypothalamus of female rats. Ligand binding studies indicated that 48 h exposure to estradiol decreases the number of alpha 2-adrenergic receptors in the agonist high affinity state. In the present studies, when(More)
These studies examined which alpha 2-adrenoceptor subtype is expressed in the hypothalamus and preoptic area and the influence of estradiol administration on alpha 2-adrenoceptors in the hypothalamus of female rats. The alpha 2-adrenoceptor antagonist [3H] RX821002 bound to a single site in hypothalamus, preoptic area, and cortex membranes, with high(More)