Miranda D. Johnson

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Nitric oxide has recently been implicated as a neurotransmitter, and may modulate synaptic transmission, cerebral blood flow, and neurotoxicity. NADPH diaphorase histochemistry has been shown to be a reliable marker for nitric oxide synthase, the enzyme that synthesizes nitric oxide, in the nervous system. Because monoaminergic neurons frequently contain(More)
Recent electrophysiological investigations in this laboratory have shown that cultured mesopontine serotonergic neurons from neonatal rats evoke serotonergic and/or glutamatergic responses in themselves and in non-serotonergic neurons. Serotonergic nerve terminals in vivo are heterogeneous with respect to vesicle type, synaptic structure, and the frequency(More)
Serotonin modulates a variety of neural processes, and is present in a subpopulation of neurons in the raphe nuclei. To study their electrophysiological properties, cells from the mesopontine raphe nuclei of the neonatal rat were dissociated and grown for up to 10 weeks in microcultures. Approximately one third of the neurons were identified as serotonergic(More)
Amylin acts acutely via the area postrema to reduce food intake and body weight, but it also interacts with leptin over longer periods of time, possibly via the ventromedial hypothalamus (VMH), to increase leptin signaling and phosphorylation of STAT3. We postulated that amylin enhances VMH leptin signaling by inducing interleukin (IL)-6, which then(More)
This study examined the influence of age on angiotensin II (AII)-stimulated vascular contractile responses and inositol phosphate (IP) accumulation in Fischer 344 rats. In the aorta, AII-stimulated contraction and IP accumulation were markedly reduced in 6- and 24-month-old rats compared to 1-month-old rats. There was not a significant difference in the(More)
Selectively bred diet-induced obese (DIO) rats become obese on a high-fat diet and are leptin resistant before becoming obese. Compared with diet-resistant (DR) neonates, DIO neonates have impaired leptin-dependent arcuate (ARC) neuropeptide Y/agouti-related peptide (NPY/AgRP) and α-melanocyte-stimulating hormone (α-MSH; from proopiomelanocortin (POMC)(More)
We previously demonstrated an age-related decline in K(+)-induced norepinephrine (NE) release from cardiac synaptosomes prepared from 6- and 24-month-old male F344 rats. The purpose of the present study was to determine if the age-related decrease in NE release seen in male F344 rats is also present in female F344 rats. K(+)-induced NE release was assessed(More)
The purpose of this study was to determine if the age-related decrease in norepinephrine (NE) release from cardiac adrenergic nerve terminals is due to a defect in Ca2+ movement into the nerve terminal or to an alteration in Ca2+ activation of intracellular events leading to NE release. NE release was assessed in cardiac synaptosomes prepared from 6- and(More)
A cardiac synaptosomal preparation developed by this laboratory was used to study neuronal calcium channels in aging rat heart. Ca2+ channels were quantified by measuring binding of iodinated omega conotoxin, which is reported to specifically block neuronal Ca2+ channels. We determined the binding of [125I]-omega conotoxin GVIA to a synaptosomal preparation(More)