Direct and indirect stimulations of cyclic AMP formation in human brain

Abstract

1 Adenosine 3':5'-cyclic monophosphate (cyclic AMP) formation, by use of an [3H]-adenine prelabelling assay, was measured in fragments of human cerebral cortex, taken in the course of various neurosurgical procedures. 2 Large accumulations of [3H]-cyclic AMP due to isoprenaline, noradrenaline and adenosine and small effects due to forskolin were observed. Histamine, 5-hydroxytryptamine (5-HT) and the excitatory amino acids glutamate and quisqualate were ineffective.3 The response to noradrenaline consisted of two components; a direct P-adrenoceptor response and an enhancement mediated by an a-adrenoceptor which appears to be similar to that in rat cerebral cortex.4 The response to isoprenaline was also potentiated by histamine H, receptor stimulation but the direct effect of 2-chloroadenosine was not altered by histamine, 5-HT or quisqualate. 5 It is concluded that some, but not all, of the indirect modulations of cyclic AMP formation previously observed in experimental animal brain exist in human cerebral cortex.

Cerium ions in the histochemical demonstration of second-messenger enzymes

“…The pre-and postsynaptic localizations of AC activities induced by specific neurotransmitter stimulations are in general agreement with biochemical, neurophysiological, and pharmacological observations (see, e.g., Greengard et al, 1972Greengard et al, , 1991Kendall et al, 1992). It was histochemically possible to locate certain types of synapses in different brain areas, e.g., in hippocampus certain neuronal circuits exhibited glutamate receptors of the kainate type, which were functionally most probably coupled to AC in a G-protein-regulated manner (Varga et al, 1996).…”

Characterization of the human brain putative A2B adenosine receptor expressed in Chinese hamster ovary (CHO.A2B4) cells

“…Similarly, PD 155,199 (A1: A2A-selective) and DPCPX (Al-selective) were poor antagonists at these receptors. In tissue slices from the human brain taken at surgery, nonselective adenosine receptor agonists evoked cyclic AMP responses greater than those to forskolin or agonists of f,-adrenoceptors or histamine receptors (Kendall et al, 1992). However, analysis of adenosine receptors in 'vital' human brain samples is necessarily hindered by problems of tissue availability and the heterogeneity in the life history of the donors.…”

Alterations of G‐protein Coupling Function in Phosphoinositide Signalling Pathways of Rat Hippocampus by Ischaemic Brain Injury

“…It is also possible that the action of A1F; actually results from its effects on different G -proteins linked to other transduction systems (CAMP formation), which may indirectly modulate InsP, formation. However, AIF; stimulates cAMP formation to a similar extent in slices from control and ischaemic rats (unpublished results), and glutamate fails to stimulate cAMP formation in the rat brain (Kendall, 1992).…”