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Wang SJ, Coutinho V, Sihra TS: Presynaptic cross-talk of beta-adrenoreceptor and 5-hydroxytryptamine receptor signalling in the modulation of glutamate release from cerebrocortical nerve terminals. Br J Pharmacol. 2002 Dec;137(8):1371-9.
1. The presynaptic interactions between facilitatory beta-adrenoreceptors and inhibitory 5-hydroxytryptamine (5-HT) receptors modulating glutamate release from cerebrocortical nerve terminals were examined. 2. 4-aminopyridine (4-AP, 1 mM)-evoked glutamate release was facilitated by the membrane permeant cyclic-3',5'-adenosine monophosphate (cAMP) analogue, 8-bromo-cAMP (8-Br-cAMP), used to directly activate cAMP-dependent protein kinase (PKA). 3. The beta-adrenoreceptor agonist, isoprenaline (ISO), effected a concentration-dependent potentiation of 4-AP-evoked glutamate release which was abolished by the beta-adrenoreceptor antagonist, propranolol, and the PKA inhibitor, Rp-cyclic-3',5'-adenosine-monophosphothioate (Rp-cAMPS). 4. 5-HT receptor activation by 100 microM 5-HT produced an inhibition of 4-AP-evoked glutamate release in nerve terminals. The inhibitory effect of 5-HT could be mimicked by the selective 5-HT (1A) receptor agonist, 8-hydroxy-dipropylaminotetralin (8-OH-DPAT) and antagonized by 1-(2-methoxyphenyl)-4-(4-phthalimidobutyl) piperazine (NAN-190). 5. When 5-HT (or 8-OH-DPAT) was used in conjunction with ISO or 8-Br-cAMP, the beta-adrenoreceptor- and PKA-mediated potentiation of glutamate release was abrogated. 6. The inhibitory crosstalk of 5-HT (1A) receptors to beta-adrenoceptor-mediated facilitation of glutamate release was abolished in the presence of NAN-190. 7. Examination of voltage-dependent Ca (2+) influx revealed that, while ISO and 5-HT alone caused a respective potentiation and diminution of the 4-AP-evoked increase in [Ca (2+)](c), the co-presence of 5-HT abolished the ISO mediated potentiation of Ca (2+) influx. 8. Together, these results suggest that beta-adrenoreceptors and 5-HT (1A) receptors coexist on the cerebrocortical nerve terminals and that the cross-talk between the two receptor signalling pathways occurs at a locus downstream from cAMP production, possibly at the level of voltage-dependent Ca (2+) influx. |
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