Decreased excitability of locus coeruleus neurons during hypercapnia is exaggerated in the streptozotocin-model of Alzheimer's disease

Author(s)

Vicente, Mariane C. ^{[1, 2]} ; Humphrey, Chuma M. ^[3] ; Gargaglioni, Luciane H. ^[1] ; Ostrowski, Tim D. ^[2]

Affiliation

^[1] Sao Paulo State Univ UNESP FCAV Jaboticabal, Dept Anim Morphol & Physiol, Jaboticabal, SP - Brazil

^[2] AT Still Univ Hlth Sci, Kirksville Coll Osteopath Med, Dept Physiol, 800 W Jefferson St, Kirksville, MO 63501 - USA

^[3] Truman State Univ, Dept Biol, Kirksville, MO - USA

• Document type: Journal article
• Source: Experimental Neurology; v. 328, JUN 2020.
• Web of Science Citations: 0

Abstract

The locus coeruleus (LC) is a pontine nucleus important for respiratory control and central chemoreception. It is affected in Alzheimer's disease (AD) and alteration of LC cell function may account for respiratory problems observed in AD patients. In the current study, we tested the electrophysiological properties and CO2/pH sensitivity of LC neurons in a model for AD. Sporadic AD was induced in rats by intracerebroventricular injection of 2 mg/kg streptozotocin (STZ), which induces behavioral and molecular impairments found in AD. LC neurons were recorded using the patch clamp technique and tested for responses to CO2 (10% CO2, pH = 7.0). The majority (similar to 60%) of noradrenergic LC neurons in adult rats were inhibited by CO2 exposure as indicated by a significant decrease in action potential (AP) discharge to step depolarizations. The STZ-AD rat model had a greater sensitivity to CO2 than controls. The increased CO2-sensitivity was demonstrated by a significantly stronger inhibition of activity during hypercapnia that was in part due to hyperpolarization of the resting membrane potential. Reduction of AP discharge in both groups was generally accompanied by lower LC network activity, depolarized AP threshold, increased AP repolarization, and increased current through a subpopulation of voltage-gated K+ channels (K-V). The latter was indicated by enhanced transient K-V currents particularly in the STZ-AD group. Interestingly, steady-state K-V currents were reduced under hypercapnia, a change that would favor enhanced AP discharge. However, the collective response of most LC neurons in adult rats, and particularly those in the STZ-AD group, was inhibited by CO2. (AU)

• FAPESP's process: 17/21750-9 - Electrophysiological properties of the noradrenergic neurons of locus coeruleus in an experimental model for Alzheimer's Disease
• Grantee: Mariane Cristine Vicente
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate