Abstract
The insular cortex (IC) processes multimodal sensory information including gustatory, visceral, nociceptive, and thermal sensation, and is considered to play a role in the regulation of homeostasis. The IC receives dense histaminergic projection from the tuberomamillary nucleus in the hypothalamus, and recent studies have demonstrated that the blockage of histaminergic receptors impairs physiological functions in the IC. However, little is known about the effects of histamine on the electrophysiological properties of the IC. To explore the effects of histamine on the subthreshold responses and action potential properties in the IC, intracellular recording with a sharp glass electrode was obtained from IC pyramidal cells in cortical slice preparations. Application of histamine (30μM) increased the frequency of repetitive spike firing in response to a long depolarizing current pulse injection; accompanied by an increase in input resistance. The frequency of repetitive spike firing was estimated by the slope of the frequency–current (f/I) curve. Histamine caused an increase from 23.3±2.3Hz/nA to 40.3±4.3Hz/nA. The histamine-induced facilitation of repetitive spike firing was blocked by pre-application of 50μM cimetidine, an H2 receptor antagonist, but not 30μM pyrilamine, an H1 receptor antagonist. R-α-methylhistamine (10μM), an H3 autoreceptor agonist, had little effect on the slope of the f/I curve. These results suggest that the histamine-induced facilitation of firing frequency is mediated via H2 and not H1 receptors. In addition, H3 receptors have a minor role in the intrinsic membrane and firing properties of IC pyramidal cells.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.