Activation of α 1-adrenoceptors increases firing frequency through protein kinase C in pyramidal neurons of rat visual cortex

• Published in: Neuroscience letters Vol. 430; no. 2; pp. 175 - 180
• Main Authors: Kobayashi, Masayuki, Sasabe, Tetsuya, Shiohama, Yasuteru, Koshikawa, Noriaki
• Format: Journal Article
• Language: English
• Published: Elsevier Ireland Ltd 2008
• Subjects: Action potential; Adaptation; PKC; Visual cortex; α 1-Adrenoceptor; α 1-Adrenoceptor; Visual cortex; PKC; Action potential; Adaptation
• ISSN: 0304-3940; 1872-7972
• DOI: 10.1016/j.neulet.2007.10.047

Properties of repetitive firing, including spike adaptation, are considered to play an essential role in controlling neural excitability in the central nervous system. Noradrenaline is one of major neurotranmitters that modulate repetitive firing in the cerebral cortex. Although activation of β-adrenoceptors increases firing frequency similarly to noradrenaline, it is still controversial whether α 1-adrenoceptor activation influences repetitive firing. In the present study, we examined the effects of adrenoceptor agonists on firing properties and the intracellular mechanism for α 1-adrenoceptor-dependent modulation of firing in pyramidal neurons of rat cerebral cortex. In agreement with previous reports, bath application of 100 μM isoproterenol, a β-adrenoceptor agonist, increased firing frequency in response to a long intracellular depolarizing current injection. Phenylephrine (100 μM), an α 1-adrenoceptor agonist, also increased firing rate, which was inhibited by 100 μM prazosin, an α 1-adrenoceptor antagonist. The extent of increment in firing rate is comparable to that induced by isoproterenol. Furthermore, phenylephrine's effects on firing properties were mimicked by 2–5 μM phorbol ester, a protein kinase C (PKC) activator, and pre-application of 10 μM chelerythrine, a PKC inhibitor, prevented phenylephrine-induced facilitation of repetitive firing. These results suggest that phenylephrine has a facilitatory effect on repetitive firing through PKC activation.