At many central excitatory synapses, AMPA receptors relay the electrical signal, whereas activation of NMDA receptors is conditional and serves a modulatory function. We show here quite a different role for NMDA receptors at dendrodendritic synapses between mitral and granule cells in the rat olfactory bulb. In whole-cell patch-clamp recordings in bulb slices, stimulation of mitral cells elicited slowly decaying, GABA A receptor-mediated reciprocal IPSCs that reflected prolonged GABA release from granule cells. Although granule cells had a normal complement of AMPA and NMDA receptors, the IPSC was completely blocked by the NMDA receptor antagonist D,L-AP-5, suggesting that NMDA receptor activation is an absolute requirement for dendrodendritic inhibition. The AMPA receptor antagonist 1,2,3,4-tetrahydro-6-nitro-2,3-dioxobenzo[f]quinoxaline-7-sulfonamide (NBQX) had no effect on IPSCs in the absence of extracellular magnesium but modestly reduced IPSCs in 1 mM magnesium, indicating that the primary effect of the AMPA receptor-mediated depolarization was to facilitate the unblocking of NMDA receptors. Granule cell voltage recordings indicated that effective spike stimulation in granule cells depended on the slow NMDA receptor kinetics. Granule cells also showed a pronounced delay between synaptic stimulation and action potential generation, suggesting that their intrinsic membrane properties underlie the ineffectiveness of brief AMPA receptor-mediated EPSPs. NMDA receptors also seem to have a central role in dendrodendritic inhibition in vivo, because intraperitoneal dizocilpine maleate (MK-801) injection in young adult rats resulted in disinhibition of mitral cells as measured by the generation of c-fos mRNA. The unique dependence of dendrodendritic inhibition on slow EPSPs generated by NMDA receptors suggests that olfactory information processing depends on long-lasting reciprocal and lateral inhibition.

OBJECTIVE -This study evaluated the efficacy and safety of vardenafil treatment for erectile dysfunction (ED) in men with diabetes.RESEARCH DESIGN AND METHODS -In this prospective multicenter double-blind placebo-controlled fixed-dose parallel-group phase III trial, 452 patients with diabetes (type 1 or type 2) and ED were randomized to take 10 or 20 mg vardenafil or placebo as needed for 12 weeks. Efficacy responses were assessed by International Index of Erectile Function domain scores, rates of vaginal penetration and successful intercourse, and a global assessment question (GAQ) about erection improvement during the previous 4 weeks. RESULTS-After 12 weeks of treatment, a dose-dependent (P ϭ 0.02) improvement in erections was noted for the GAQ, with 57 and 72% of men taking 10 mg or 20 mg vardenafil, respectively, reporting improved erections, in contrast to 13% after taking placebo (P Ͻ 0.0001). For the erectile function domain, dose-dependent (P ϭ 0.03) final scores for the 10-and 20-mg dose were 17.1 and 19.0 compared with 12.6 for placebo (P Ͻ 0.0001). Both vardenafil doses significantly enhanced the rates of successful penetration (P Ͻ 0.0001) and successful intercourse (P Ͻ 0.0001) compared with placebo. Vardenafil treatment was effective in increasing intercourse success rates at all levels of baseline ED severity, at each level of plasma HbA 1c , and for type 1 and 2 diabetes. Treatment-emergent adverse events were primarily mild to moderate headache (Յ13%), flushing (Յ10%), and rhinitis (Յ10%).CONCLUSIONS -Vardenafil statistically improved erectile function and was generally well tolerated in these diabetic patients with ED. Diabetes Care 26:777-783, 2003E rectile dysfunction (ED), the consistent or recurrent inability to attain and/or maintain a penile erection sufficient for sexual performance (1), can have a significant effect on a patient's quality of life (2-4). ED is a common complication of diabetes because Ͼ50% of diabetic men develop ED within 10 years of being diagnosed with diabetes (5). The prevalence of ED increases with age, from 9% in diabetic men ages 20 -29 years to 95% in diabetic men Ͼ70 years (5), and increases with duration, poor control, and complications of diabetes (such as vascular and microvascular disease and neuropathies) (6).Diabetic men with ED tend to be less responsive to treatment perhaps because the pathogenesis of diabetes-associated ED is likely to be multifactorial (7,8). Although treatment with phosphodiesterase type 5 (PDE5) inhibitors is less effective in the diabetic patient than in the nondiabetic ED patient, the convenience of an orally formulated PDE5 inhibitor has popularized treatment in a large number of men with diabetes and ED (9,10).Vardenafil, a new PDE5 inhibitor, is more selective for PDE5 and more biochemically potent than sildenafil in in vitro and in vivo studies when tested under the same conditions (11-13). These properties suggest that vardenafil may be a highly efficacious oral treatment in the difficult-to-treat ED patients with diabetes. ...

Thyroid hormone is important in the regulation of synthesis and secretion of thyroid-stimulating hormone (TSH) in the anterior pituitary, but its role in the control of hypothalamic thyrotropin-releasing hormone (TRH) is controversial. To determine whether thyroid hormone regulates the function of TRH in the hypothalamic tuberoinfundibular system, a study was made of the effect of hypothyroidism on thyrotropin-releasing hormone messenger RNA (proTRH mRNA) and TRH prohormone in the rat paraventricular nucleus. Extracts of rat hypothalamic paraventricular nucleus were examined by quantitative Northern blot analysis, and coronal sections of rat brain were examined by in situ hybridization histochemistry and immunocytochemistry. A nearly twofold increase in proTRH mRNA was observed in hypothyroid animals; this increase could be obliterated by levothyroxine treatment, suggesting an inverse relation between circulating thyroid hormone and proTRH mRNA. In situ hybridization showed that this response occurred exclusively in medial parvocellular neurons of the paraventricular nucleus. A simultaneous increase in proTRH mRNA and immunoreactive TRH prohormone in this region suggests that hypothyroidism induces both transcription and translation of the TRH prohormone in the paraventricular nucleus.

The amphibian tetradecapeptide bombesin and its mammalian homolog gastrin-releasing peptide are neurotransmitters and paracrine hormones, and are mitogenic for fibroblast and small cell lung carcinoma cell lines. cDNAs encoding the bombesin/gastrin-releasing peptide receptor (BR) expressed by murine Swiss 3T3 fibroblasts were isolated using electrophysiological and luminometric Xenopus oocyte expression assays. Oocytes microinjected with BR transcripts responded to concentrations of bombesin from 1 x 10(-10) to 1 x 10(-6) M. These responses showed homologous desensitization and could be specifically blocked by bombesin antagonists. Sequence analysis showed that the BR has seven membrane-spanning domains and five potential N-linked glycosylation sites. Data base analysis showed that the BR is most homologous to the tachykinin receptors. Although tyrosine kinase activity has been associated with BR function, no tyrosine kinase homologies occur within the BR sequence.