SITE OF ACTION OF SYSTEMIC GAMMA-AMINOBUTYRIC ACID IN THE SPINAL CORD

Publisher Website
Google Scholar
Abstract
In acute unanaesthe-tized spinal cats, intravenous injection of GABA in concentrations above 0. 30 mg/kg consistently depressed the extensor monosynaptic reflex, while the flexor monosynaptic reflex was usually facilitated. The action of GABA gradually decreased when systemic administration was repeated within short intervals. The action of GABA was not demon -stratable in decerebrate cats. The effect of GABA on the flexor mono-synaptic reflex was altered by changes in internuncial activity produced by cutaneous, Group II and III afferent conditioning volleys. GABA action was not influenced by Group I afferent and antidromic axonal collateral conditioning volleys. Nembutal anaesthesia resulted in elimination of GABA action. Strychnine abolished or reduced the facilitatory effect of GABA on the flexor monosynaptic reflex. It was concluded that GABA may selectively block some excitatory inter-neurones which are intercalated in the reflex pathways of Group II and III fibers of muscle nerve and of some cutaneous afferent fibres and are tonically controlled by suprasegmental activity.