ANESTHESIA AND THE RESPONSIVENESS OF INDIVIDUAL NEURONS OF THE CAUDATE NUCLEUS OF THE CAT TO ACETYLCHOLINE, NOREPINEPHRINE AND DOPAMINE ADMINISTERED BY MICROELECTROPHORESIS

Abstract

The responsiveness of spontaneously active caudate nucleus neurons to the administration by electrophoresis of ACh, NE and DOPAM as well as of glutamate, dl -homocysteic acid and γ-aminobutyric acid at the site of recording was investigated in unanesthetized, decerebrate cats and in animals variously anesthetized. Most units in the unanesthetized preparations responded to ACh with a facilitation and to NE and DOPAM with a depression of their spontaneous discharge rates; some responded in the opposite direction. Depression by NE and DOPAM on occasion persisted for several minutes, during which facilitatory responses to ACh were greatly reduced. Unit facilitation by ACh was reversibly diminished or suppressed by small to moderate doses of short-acting barbiturates or ether or by the electrophoretic administration of procaine in the vicinity of the recorded neuron, although ACh-induced depression as well as responsiveness to NE, DOPAM, glutamate and γ-aminobutyric acid remained unchanged. Depression was the predominant response to ACh of spontaneously active caudate units in fully anesthetized animals and of units which were not spontaneously active in unanesthetized animals but were made to fire by the continuous electrophoretic administration of glutamate.