Gerald J McLaren

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1. Pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) was investigated for its ability to act as an antagonist at P2x-purinoceptors which mediate neurogenic excitatory junction potentials (e.j.ps) and contractions in the guinea-pig isolated vas deferens. 2. PPADS (10(-7) M) caused a small potentiation of the phasic, predominantly purinergic(More)
1. The site(s) at which P2-receptor agonists act to evoke contractions of the rat isolated tail artery was studied by use of P2-receptor antagonists and the extracellular ATPase inhibitor 6-N,N-diethyl-D-beta,gamma-dibromomethyleneATP (ARL 67156). 2. Suramin (1 microM(-1) mM) and pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) (0.3-300 microM)(More)
Interstitial cells of Cajal (ICC) provide important regulatory functions in the motor activity of the gastrointestinal tract. In the small intestine, ICC in the myenteric region (ICC-MY), between the circular and longitudinal muscle layers, generate and propagate electrical slow waves. Another population of ICC lies in the plane of the deep muscular plexus(More)
1. Interstitial cells of Cajal (ICCs) have been identified as pacemaker cells in the gastrointestinal (GI) tracts of vertebrates. We have studied the development of ICCs in pacemaker regions and the onset of electrical rhythmicity in the gastric antrum, small bowel and proximal colon of the mouse. 2. ICCs, as detected by c-Kit immunofluorescence, were found(More)
The patterns and density of channels expressed in neurons critically determine their electrical properties. We have examined developmental regulation of Ca2+-channel expression during the maturation of the spinal motor circuits in Xenopus as it develops from an embryo to a larva. In embryonic neurons approximately 60% of the current is carried by N-type(More)
ATP and noradrenaline are co-stored in synaptic vesicles in sympathetic nerves and when co-released act postjunctionally to evoke contraction of visceral and vascular smooth muscle. In the original purinergic nerve hypothesis it was proposed that ATP would then be sequentially broken down to ADP, AMP and adenosine. Although such breakdown can be measured,(More)
Intracellular microelectrode recording was used to examine the effects of suramin, a P2-purinoceptor antagonist, on the electrical responses evoked by sympathetic nerve stimulation in the rat isolated tail artery. Field stimulation (10 or 20 pulses at 0.5, 1 and 2 Hz) evoked a biphasic electrical response, consisting of fast, transient excitatory junctional(More)
The actions of ATP and uridine 5'-triphosphate (UTP) were compared at P2X1 receptors in acutely dissociated smooth muscles cells of the rat tail artery. ATP (30 nM-100 microM) and UTP (1 microM-1 mM) elicited concentration-dependent inward currents. ATP was approximately 100-fold more potent than UTP. In both cases, currents were activated within 3 ms of(More)
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