Single-unit recordings of arterial chemoreceptors from mouse petrosal ganglia in vitro

Abstract

A preparation was developed that allows for the recording of single-unit chemoreceptor activity from mouse carotid body in vitro. An anesthetized mouse was decapitated, and each carotid body was harvested, along with the sinus nerve, glossopharyngeal nerve, and petrosal ganglia. After exposure to collagenase/trypsin, the cleaned complex was transferred to a recording chamber where it was superfused with oxygenated saline. The ganglia was searched for evoked or spontaneous unit activity by using a glass suction electrode. Single-unit action potentials were 57 +/- 10 (SE) (n = 16) standard deviations above the recording noise, and spontaneous spikes were generated as a random process. Decreasing superfusate PO(2) to near 20 Torr caused an increase in spiking activity from 1. 3 +/- 0.4 to 14.1 +/- 1.9 Hz (n = 16). The use of mice for chemoreceptor studies may be advantageous because targeted gene deletions are well developed in the mouse model and may be useful in addressing unresolved questions regarding the mechanism of chemotransduction.

Kv1.1 Deletion Augments the Afferent Hypoxic Chemosensory Pathway and Respiration

“…Kv1.1 was identified in afferent chemosensory fibers and their cell bodies in the petrosal ganglia. In the rat, the majority of carotid sinus fibers are unmyelinated C-fibers (McDonald, 1983), and data from the mouse indicate the same (Donnelly and Rigual, 2000). In C-type sensory neurons, blockade of ␣-DTX-sensitive currents (Kv1.1, -1.2, -1.6) increased the number and frequency of action potentials in response to depolarization (Stansfeld et al, 1986;Glazebrook et al, 2002).…”

“…EPSCs were generated by placing a concentric bipolar stimulating electrode (Frederick Haer, Bowdoinham, ME) on the solitary tract (TS) con-taining chemosensory as well as other visceral afferents (Andresen and Kunze, 1994) and stimulating (0.1 ms duration) at frequencies of 0.5, 1, 5, 10, 20, and 50 Hz with an isolated programmable stimulator (AMPI, Jerusalem, Israel). Stimulus frequencies were determined, in part, from studies showing mouse chemosensory afferent single fibers increase discharge from ϳ1 to 20 Hz during hypoxia (Donnelly and Rigual, 2000;Rigual et al 2002). In experiments in which we wished to record spontaneous miniature EPSCs (mEPSCs), the recording electrodes contained the following (in mM): 5 NaCl, 130 Cs ϩ methanesulfonate, 10 CsCl, 11 EGTA, 1 CaCl 2 , 10 HEPES, 1 MgCl 2 , 2 MgATP, 0.2 NaGTP, and 5 lidocaine N-ethyl bromide (QX-314), pH 7.3, whereas the extracellular solution contained 1.0 M tetrodotoxin (TTX) and 10 M bicuculline methobromide.…”

Morphological differences of the carotid body among C57/BL6 (B6), A/J, and CSS B6A1 mouse strains

“…The carotid body was located using standard anatomical landmarks as described by Donnelly and Rigual (2000). Upon extraction, the carotid bifurcation was immediately immersed in neutrally buffered 10% formalin.…”

A Mouse Model of Pharyngeal Dysphagia in Amyotrophic Lateral Sclerosis

“…Animals were anesthetized by hind limb intramuscular injection of a ketamine (90 mg/kg) and xylazine (10 mg/kg) solution with an initial dose of 0.01 ml per 10 g body weight, followed by a half dose every 20 min as needed to maintain adequate anesthesia. An adequate level of anesthesia was indicated in WT mice by the absence of hind limb and forelimb reflexes in response to noxious pinch (using blunt forceps) stimulation of the hindpaw and forepaw [49,50]. Hindpaw reflexes were expected to be diminished in SOD1-G93A transgenic mice, so an adequate depth of anesthesia for transgenic mice was indicated by the absence of reflexes when applying noxious pinch stimulation to the forepaws and ears [49,51] and by the absence of the blink reflex and vibrissae movement in response to gentle blowing of air on the face [51].…”