ELECTROCORTICAL CHANGES INDUCED BY THE PERFUSION OF NORADRENALINE, ACETYLCHOLINE AND THEIR ANTAGONISTS DIRECTLY INTO THE DORSAL RAPHÉ NUCLEUS OF THE CAT

Abstract

1 The electrocortical changes induced by the perfusion of drugs directly into the dorsal raphé nucleus of the cat encéphale isolé preparation have been studied. 2 (−)-Noradrenaline (NA), (−)-adrenaline, or (−)-isoprenaline (Isop) produced intermittent or sustained electrocortical desynchronization during the perfusion period. 3 These changes were markedly attenuated or completely abolished by the prior perfusion of (±)-sotalol or (−)-propranolol, but not by equimolecular concentrations of (+)-propranolol. 4 The effects of NA or Isop were also blocked by phentolamine, whereas phenoxybenzamine either potentiated the responses to NA and Isop or mimicked the effects of these catecholamines. 5 The effect of dopamine was similar to that induced by NA, but could not be elicited at all of the perfusion sites where NA was effective. It could be blocked by (±)-sotalol or (−)-propranolol and also by the prior perfusion of fusaric acid. 6 Acetylcholine (ACh) increased, or initiated, electrocortical synchronization. These effects could be antagonized by sensory stimulation, the prior perfusion of atropine, or the simultaneous perfusion of NA at the same site. 7 Lignocaine, induced prolonged electrocortical desynchronization, behavioural alerting and an increased responsiveness to sensory stimulation. 8 The results have been discussed in relation to the possible involvement of inhibitory β-adrenoceptors and facilitatory cholinoceptors (muscarinic) in the functioning of the dorsal raphé nucleus.