[Effect of bulbar microinjections of noradrenaline, isoproterenol and phentolamine on the spino-bulbo-spinal reflex in the cat].

In chloralose-anesthetized cats a long lasting depression of spino-bulbo-spinal (SBS) reflex discharges following microinjections of noradrenaline and its agonist (isoproterenol) in the medial bulbar reticular formation was revealed. Microinjections of phentolamine (alpha-adrenoceptor antagonist) were followed by prominent enhancement of SBS-reflexes. Depressive action of the locus coeruleus stimulation on SBS-responses essentially decreased after these microinjections. The data evidence for a specific noradrenergic nature of inhibitory locus coeruleus influences on reticular centre of SBS-reflexes.