A role for the Kölliker-Fuse nucleus in cholinergic modulation of breathing at night during wakefulness and NREM sleep

Abstract

To probe further the contributions of cholinergic rostral pontine systems in control of breathing, we designed this study to test the hypothesis that microdialysis (MD) of the muscarinic receptor antagonist atropine into the pontine respiratory group (PRG) would decrease breathing more in animals while awake than while in NREM sleep. In 16 goats, cannulas were bilaterally implanted into rostral pontine tegmental nuclei (n ϭ 3), the lateral (n ϭ 3) or medial (n ϭ 4) parabrachial nuclei, or the Kölliker-Fuse nucleus (KFN; n ϭ 6). After Ͼ2 wk of recovery from surgery, the goats were studied during a 45-min period of MD with mock cerebrospinal fluid (mCSF), followed by at least 30 min of recovery and a second 45-min period of MD with atropine. Unilateral and bilateral MD studies were completed during the day and at night. MD of atropine into the KFN at night decreased pulmonary ventilation and breathing frequency and increased inspiratory and expiratory time by 12-14% during both wakefulness and NREM sleep. However, during daytime studies, MD of atropine into the KFN had no effect on these variables. Unilateral and bilateral nighttime MD of atropine into the KFN increased levels of NREM sleep by 63 and 365%, respectively. MD during the day or at night into the other three pontine sites had minimal effects on any variable studied. Finally, compared with MD of mCSF, bilateral MD of atropine decreased levels of acetylcholine and choline in the effluent dialysis fluid. Our data support the concept that the KFN is a significant contributor to cholinergically modulated control of breathing and sleep.non-rapid eye movement sleep; pons FOR MANY YEARS, ACETYLCHOLINE (ACh) has been known to play a role in the control of breathing (14) and sleep (3). In the medial pontine reticular formation (mPRF), endogenous ACh release causes state-dependent changes in respiratory control (2) and can stimulate rapid eye movement (REM) sleep (22). Microadministration of the cholinergic agonists carbachol (mixed cholinergic agonist), bethanechol (muscarinic agonist), and neostigmine (acetylcholine esterase inhibitor) into the mPRF are all known to generate this effect (1,2,18,22,27), whereas the muscarinic antagonist atropine can block this effect (1). Indeed, mPRF cholinoceptive mechanisms can cause state-dependent changes in the firing rates of respiratory neurons in the parabrachial nuclei (16). These studies provide evidence of anatomic connectivity from the mPRF to the pontine respiratory group (PRG). Evidence of projections in the reverse direction, from the PRG to the mPRF, is provided by microinjection of fluorescent dyes into the PRG, resulting in ipsi-and contralateral positive regions in the mPRF as well as in the dorsal respiratory group and ventral respiratory group in the medulla (20). However, studies of the connectivity between brain stem respiratory neurons performed using chronically implanted arrays of microelectrodes emphasized "a sparse distribution of functional connections," which suggests that interactions between brai...

Atropine microdialysis within or near the pre-Bötzinger Complex increases breathing frequency more during wakefulness than during NREM sleep

“…Generally, the expression of each mAChR subtype was slightly higher in the LPBN and MPBN than in the KFN. We have documented the presence of M 2 mAChRs in all three of these nuclei in goats (8). In addition, dialysis of atropine in the LPBN and MPBN had no effect on breathing during the day and night (awake or NREM sleep) (8).…”

“…We have documented the presence of M 2 mAChRs in all three of these nuclei in goats (8). In addition, dialysis of atropine in the LPBN and MPBN had no effect on breathing during the day and night (awake or NREM sleep) (8). However, dialysis of atropine in the KFN decreased breathing frequency at night while awake and during NREM sleep but had no effect during the day while awake (8).…”

“…The perfusate was either mock cerebrospinal fluid (mCSF: 124 mM NaCl, 2.0 mM KCl, 2.0 mM MgCl 2, 1.3 mM K2PO4, 2.0 mM CaCl 2, 11 mM glucose, 26 mM NaHCO 3 Ϫ , and pH 7.32 in sterile distilled H 2O) alone or atropine (50 mM; Sigma) dissolved in mCSF. Previous in vitro studies in the laboratory have established that atropine crosses the membrane (8). Dialyzed solutions were warmed to 39°C and equilibrated with 6.4% CO 2 and 21% O2 balanced with N 2 in a tonometer.…”

“…For example, the pontine respiratory group (PRG) nuclei express M 1 -M 3 mAChRs (34). The predominant effect of cholinergic modulation of PRG neurons within the Kölliker-Fuse Nucleus (KFN) appears to be excitatory, since reverse dialysis of the nonselective mAChR antagonist atropine reduced minute ventilation (V I ) and breathing frequency in both the awake state and during non-rapid-eye-movement (NREM) sleep at night, but not while awake during the day in unanesthetized goats (8). These effects were specific to the KFN, since breathing was not decreased during atropine dialysis in three other rostral pontine nuclei.…”

Contributions of the Kölliker–Fuse nucleus to coordination of breathing and swallowing

“…Data reported herein were obtained as part of a larger experimental series that determined the effects on breathing of attenuating cholinergic modulation with atropine (Bonis et al, 2010a) and effects of neurotoxic lesions in the dorsolateral pons (Bonis et al, 2010b). Thus, the experimental design and surgical procedures have been reported previously (Bonis et al, 2010b).…”