Inhibitory gating of single unit activity in amygdala: effects of ketamine, haloperidol, or nicotine.
BACKGROUND
Inhibitory gating is thought to be a basic process for filtering incoming stimuli to the brain. Little information is currently available concerning local neural networks of inhibitory gating or the intrinsic neurochemical substrates involved in the process.


METHODS
The goal of the present study was to examine the pharmacological aspects of inhibitory gating from single units in the amygdala. We tested the effects of ketamine (80 mg/kg) and haloperidol (1 mg/kg) on inhibitory gating. Additionally, we examined the effect of nicotine (1.2 mg/kg) on single unit gating in this same brain structure.


RESULTS
We found that in one subset of neurons, ketamine administration significantly reduced tone responsiveness with a subsequent loss of inhibitory gating, whereas the other subset persisted in both auditory responding and gating albeit at a weaker level. Haloperidol and nicotine had very similar effects, exemplified by a dramatic increase in the response to the initial "conditioning" tone with a subsequent improvement in inhibitory gating.


CONCLUSIONS
Tone responsiveness and inhibitory gating persists in a subset of neurons after glutamate N-methyl-D-aspartate receptor blockade. Dopamine and nicotine modulate gating in these normal animals and have similar effects of enhancing responsiveness to auditory stimulation at the single unit and evoked potential level.
Cromwell
Howard C
HC
Department of Physiology and Pharmacology, School of Medicine, Wake Forest University, Winston-Salem, North Carolina, USA. hcc@bgsu.edu
Woodward
Donald J
DJ
D000161:Acoustic Stimulation / Q000379:methods; D000200:Action Potentials / Q000187:drug effects*; D000679:Amygdala / Q000166:cytology* / Q000187:drug effects; D000818:Animals; D018492:Dopamine Antagonists / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D006220:Haloperidol / Q000494:pharmacology*; D007649:Ketamine / Q000494:pharmacology*; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects*; D009538:Nicotine / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013216:Reflex, Startle / Q000187:drug effects / Q000528:radiation effects
D018492:Dopamine Antagonists; D018691:Excitatory Amino Acid Antagonists; D018722:Nicotinic Agonists; D007649:Ketamine; D009538:Nicotine; D006220:Haloperidol