British journal of pharmacology
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1. Membrane properties of rat periaqueductal gray neurones were investigated by use of intracellular recordings from single neurones in brain slices. Morphological properties and anatomical location of each impaled neurone were characterized by intracellular staining with biocytin. ⋯ In conclusion, fast glutamatergic and GABAergic synaptic potentials were evoked by electrical stimulation throughout the lateral and ventrolateral periaqueductal gray. Slow inhibitory synaptic potentials were also evoked in some neurones. Opioids acting on micro-receptors inhibited both GABAergic and glutamatergic components of synaptic potentials throughout this brain region.
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1. Male, Long Evans rats (350-450 g) were chronically instrumented for the measurement of renal, mesenteric and hindquarters haemodynamics, and were given three consecutive, 24 h infusions of vehicle (sterile saline at 0.3 ml h-1, n = 8) or alpha-trinositol (D-myo-inositol-1,2,6-triphosphate) at 5, 20 and 80 mg kg-1 h-1 (0.3 ml h-1; n = 9). During infusion of alpha-trinositol at 5 or 20 mg kg-1 h-1, cardiovascular changes were little different from those seen during saline infusion. ⋯ These results, collectively, indicate that incremental infusions of alpha-trinositol do not reveal its full vasodilator potential, possibly due to concurrent activation of counter-regulatory vasoconstrictor mechanisms. However, infusion of alpha-trinositol at a high dose causes substantial increases in renal,mesenteric and hindquarters flows and vascular conductances, supported by significant increases in indices of cardiac inotropism. Such effects, in the absence of significant hypotension, tachycardia or signs of desensitization, give alpha-trinositol a unique cardiovascular profile.