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  • 1
    Electronic Resource
    Electronic Resource
    Pharmacological Evidence for the Modulation of Monoamine Release by Adenosine in the Invertebrate Nervous System (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 54 (1990), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: An in vitro preparation from the pedal ganglia of the marine bivalve, Mytilus edulis, was used to examine the modulation of transmitter release by adenosine and its analogs from invertebrate nervous tissue. The ganglia of this organism contain the monoamines dopamine (DA), serotonin (5-HT), and norepinephrine (NE), and the presynaptic release of these substances is known to be calcium-dependent. This organism also contains a DA-sensitive adenylate cyclase system which resembles that seen in mammals. Neural tissue from the pedal ganglia was incubated with labeled monoamines, and release studies were then conducted in superfusion chambers; release of monoamines was evoked by the addition of 50 mM KCl. Addition to the superfusion medium of the adenosine analog, 5′-N-ethylcarboxamidoadenosine (NECA; 10 nM), inhibited the release of 5-HT and DA, and to a lesser extent NE, whereas 100-fold higher concentrations of adenosine itself and the adenosine analog, R-N6-phenylisopropyladenosine, were required to achieve comparable levels of inhibition. The inhibitory effects of NECA on neurotransmitter release were blocked by the adenosine receptor antagonist, theophylline (IC50= 10–14 μM). The results from this study indicate for the first time the possible role of adenosine as a modulator of neurotransmitter release in the invertebrate nervous system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb04904.x
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  • 2
    Electronic Resource
    Electronic Resource
    Evidence for Presynaptic Adenosine A2a Receptors Associated with Norepinephrine Release and Their Desensitization in the Rat Nucleus Tractus Solitarius (1995)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 65 (1995), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Rat medullary brain segments containing primarily nucleus tractus solitarius (NTS) were used for superfusion studies of evoked transmitter release and for isotherm receptor binding assays. Isotherm binding assays with [3H]CGS-21680 on membranes prepared from NTS tissue blocks indicated a single high-affinity binding site with a KD of 5.1 ± 1.4 nM and a Bmax of 20.6 ± 2.4 fmol/mg of protein. The binding density for [3H]CGS-21680 on NTS membranes was 23 times less than comparable binding on membranes from striatal tissue. Electrically stimulated (1 min at 25 mA, 2 ms, 3 Hz) release of [3H]norepinephrine ([3H]NE) from 400-µm-thick NTS tissue slices resulted in an S2/S1 ratio of 0.96 ± 0.02. Superfusion of single tissue slices with 0.1–100 nM CGS-21680, a selective adenosine A2a receptor agonist, for 5 min before the S2 stimulus produced a significant concentration-dependent increase in the S2/S1 fractional release ratio that was maximal (31.3% increase) at 1.0 nM. However, superfusion of tissue slices with CGS-21680 over the same concentration range for 20 min before the S2 stimulus did not alter the S2/S1 ratio significantly from control release ratios. The augmented release of [3H]NE mediated by 1.0 nM CGS-21680 with a 5-min tissue exposure was abolished by 1.0 and 10 nM CGS-15943 as well as by 100 nM 8-(3-chlorostyryl)caffeine, both A2a receptor antagonists, but not by 1.0 nM 8-cyclopentyl-1,3-dipropylxanthine, the A1 receptor antagonist. Taken together, these results suggest that CGS-21680 augmented the evoked release of [3H]NE in the NTS via activation of presynaptic A2a receptors within the same concentration range as the binding affinity observed for [3H]CGS-21680. It was also apparent that this population of presynaptic adenosine A2a receptors in the NTS desensitized within 20 min because the augmenting action of CGS-21680 on evoked transmitter release was not evident at the longer interval.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1995.65041604.x
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  • 3
    Electronic Resource
    Electronic Resource
    Antagonism of the anti-conflict effects of phenobarbital, but not diazepam, by the A-1 adenosine agonistl-PIA (1990)
    Springer
    Psychopharmacology 102 (1990), S. 283-290 
    Details
    ISSN: 1432-2072
    Keywords: Adenosine ; Anxiety ; Conflict behavior ; Caffeine ; Conditioned Suppression of Drinking (CSD) ; Diazepam ; l-PIA ; NECA ; Phenobarbital ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present study examined the effects of the anxiolytics diazepam and phenobarbital, the A-1 adenosine agonist N6-R-phenylisopropyladenosine (l-PIA), and the A-2 adenosine agonist 5′-N-ethylcarboxamidoadenosine (NECA) on conflict behavior. Water-restricted rats were trained to drink from a tube that was electrified (0.5 mA intensity) on a FI-29s schedule, electrification being signaled by a tone. After 3 weeks of daily 10-min sessions, the animals accepted a stable number of shocks (punished responding) and consumed a consistent volume of water (unpunished responding) per session. Different doses ofl-PIA and NECA were then tested separately at weekly intervals. In addition, the effects of diazepam and phenobarbital were determined in animals pretreated with saline,l-PIA, or NECA. Neitherl-PIA (15–250 nmole/kg) nor NECA (2.5–20 nmole/kg) produced a significant anti-conflict effect when administered alone. Diazepam (1.25–10 mg/kg) or phenobarbital (10–40 mg/kg) administration to saline-pretreated rats resulted in a dose-dependent increase in punished responding (shocks received) with minimal effects on unpunished responding (water intake). Neitherl-PIA nor NECA pretreatment reliably altered the effects of diazepam on conflict behavior. Pretreatment withl-PIA, but not NECA, significantly reduced the anti-conflict effects of phenobarbital on conflict behavior. These data suggest that phenobarbital, but not diazepam, anti-conflict responses may involve interactions with A-1 adenosine receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02244091
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