engleski

Noradrenergic inputs to Inspiratory Hypoglossal Motoneurons (IHMNs) in decerebrate dogs

Noradrenergic (NA) excitatory input contributes to genioglossus muscle activity in wakefulness and non-REM sleep in rats, but is withdrawn in REM sleep. We hypothesized that NA inputs to IHMNs also contribute to their activity in decerebrate dogs. Multibarrel micropipettes were used to record extracellular activity and picoeject agonists phenylephrine (Phe: 100 μM) and Medetomidine (Med: 10 μM) or antagonists Prazosin (Pra: 50 μM) and Yohimbine (Yoh: 10 μM) on single IHMNs in vivo. Drug-induced changes in discharge frequency (Fn) patterns were analyzed using cycle- triggered histograms. Picoejected Phe increased peak and average inspiratory discharge frequency (Fn) by ~50%, showing that α1 receptors are present on IHMNs. Pra did not change baseline activity, but completely reversed Phe effects, suggesting that there is no endogenous NA activation of IHMNs. Neither Med nor Yoh had any effect on IHMN discharge. Picoejected 5HT (2 mM) increased peak Fn to 249±142% and average Fn to 221±104% from control. These results suggest that α1 adrenergic receptors are present on IHMNs, but they are not endogenously activated in decerebrate, vagotomized dogs during hyperoxic hypercapnia. It appears that α2 receptors are not present on canine IHMNs. Supported by NIH GM059234 and VA Medical Research Funds.

NA ; IHMN ; dog

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