We studied the effects of GABA receptor agonists microinjections
in medullary raphé on the mechanically induced tracheobronchial
cough response in anesthetized, unparalyzed, spontaneously
breathing cats. The results suggest that GABA-ergic inhibition
significantly contributes to the regulation of cough reflex by
action of both GABAA and GABAB receptors. The data are
consistent with inhomogeneous occurrence of GABA-ergic
neurons in medullary raphé and their different involvement in the
cough reflex control. Cells within rostral nucleus raphé obscurus
with dominant role of GABAA receptors and neurons of rostral
nucleus raphé pallidus and caudal nucleus raphé magnus with
dominant role of GABAB receptors participate in regulation of
cough expiratory efforts. These cough control elements are
distinct from cough gating mechanism. GABA-ergic inhibition in
the raphé caudal to obex had insignificant effect on cough.
Contradictory findings for GABA, muscimol and baclofen
administration in medullary raphé suggest involvement of
coordinated activity of GABA on multiple receptors affecting
raphé neurons and/or the local neuronal circuits in the raphé
modulating cough motor drive.