In this study we examined the mechanism whereby atrial natriuretic peptide secretion is increased when the frequency of contraction is raised from 2 to 5 Hz. We tested the hypothesis that calcium plays a significant role in the frequency-stimulated response. Using superfused rat left atria, we found that lowering the superfusate calcium concentration from 1.8 to 0.2 mmol/L abolished the frequen...

The pentapeptide proctolin has multiple effects on the locust oviposition digging system. At the neuromuscular junction of the ventral opener muscle, it has a concentration-dependent range of modulatory effects. At low concentrations (10210 mol l21), proctolin causes an increase in the frequency of miniature excitatory junctional potentials, but has no apparent effects on the muscle membrane or...

Group I metabotropic glutamate receptors (mGluR) on astrocytes have been shown to participate in cerebral vasodilation to neuronal activation in brain slices. Pharmacological stimulation of mGluR in brain slices can produce arteriolar constriction or dilation depending on the initial degree of vascular tone. Here, we examined whether pharmacological stimulation of mGluR in vivo increases cerebr...

OBJECTIVE We determined, via a bioassay, if inotropic factors are released in the coronary circulation of the rat heart and if changes in cardiac perfusion change papillary muscle inotropy. METHODS An isolated isometrically contracting rat papillary muscle (n = 5, acceptor) was superfused with Tyrode or with reoxygenated coronary venous effluent from an isolated isovolumically beating rat hea...

BACKGROUND Fish oil reduces sudden death in patients with prior myocardial infarction. Sudden death in heart failure may be due to triggered activity based on disturbed calcium handling. We hypothesized that superfusion with omega3-polyunsaturated fatty acids (omega3-PUFAs) from fish inhibits triggered activity in heart failure. METHODS AND RESULTS Ventricular myocytes were isolated from expl...

This study was designed to assess the role of calcitonin gene-related peptide (CGRP) and its receptor in the sensitization of dorsal horn neurons induced by intradermal injection of capsaicin in rats. Extracellular recordings were made from wide dynamic range (WDR) dorsal horn neurons with receptive fields on the hindpaw in the lumbar enlargement of anesthetized rats. The background activity an...

Application of glutamate to glial cell cultures stimulates the formation and release of epoxyeicosatrienoic acids (EETs) from arachidonic acid by cytochome P-450 epoxygenases. Epoxygenase inhibitors reduce the cerebral vasodilator response to glutamate and N-methyl-D-aspartate. We tested the hypothesis that epoxygenase inhibitors reduce the somatosensory cortical blood flow response to whisker ...

Freshly isolated rat juxtaglomerular cells (JGC) were superfused to study renin secretion rate (RSR) at the cellular level. Effluates from the superfusion chamber collected in 20-min intervals showed a time-dependent decline in RSR from 85.5 ± 32 to 4.0 ± 2.4 ng ANG I ⋅ ml-1 ⋅ h-1 ⋅ mg protein-1 ⋅ min-1within 100 min of collection (mean ± SE, n = no. of JGC preparations/superfusion chambers = 9...

Neuronal signaling, plasticity and pathologies in CA1 hippocampal neurons are all intimately related to the redox environment and, thus, tissue oxygenation. This study tests the hypothesis that hyperoxic superfusate (95%O2) causes a time-dependent increase in superoxide anion (·O2) production in CA1 neurons in slices, which will decrease as oxygen concentration is decreased. Hippocampal slices ...

Neuronal signaling, plasticity, and pathologies in CA1 hippocampal neurons are all intimately related to the redox environment and, thus tissue oxygenation. This study tests the hypothesis that hyperoxic superfusate (95% O(2)) causes a time-dependent increase in superoxide anion (*O(2)(-)) production in CA1 neurons in slices, which will decrease as oxygen concentration is decreased. Hippocampal...