Effects of microiontophoretically applied flurazepam on responses of cerebral cortical neurones to putative neurotransmitters.
Utilizing standard microiontophoretic techniques and recording extracellularly in cats, we studied the effects of flurazepam, a water-soluble benzodiazepine, on the spike activity of single cerebral neurones and its interactions with several excitatory and inhibitory putative neurotransmitters. Large iontophoretic doses (5--30 nA, 0.1 M solution) of flurazepam induced a depression of spike amplitude. Smaller doses (less than 5 nA, 0.1 M solution or 20--50 nA, 20 mM in 0.16 M NaCl) reduced the excitation produced by glutamate, aspartate, and homocysteate, but antagonism of acetylcholine-evoked excitations required large flurazepam doses (up to 30 nA, 0.1 M solution). Even lower doses of flurazepam (less than 10 nA, 20 mM in 0.16 M NaCl) enhanced the inhibitory effect of gamma-aminobutyric acid (GABA) but antagonized that of 5-hydroxytryptamine, and had no effect on dopamine-induced inhibition of firing. Hence, only GABA-evoked inhibitions were significantly potentiated by flurazepam. These results demonstrate the multiple possible interactions between a benzodiazepine and different putative neurotransmitters in the mammalian cerebral cortex.
D000109:Acetylcholine / Q000494:pharmacology; D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects*; D004298:Dopamine / Q000494:pharmacology; D005260:Female; D005479:Flurazepam / Q000008:administration & dosage / Q000494:pharmacology*; D007478:Iontophoresis; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects; D009474:Neurons / Q000187:drug effects; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D051381:Rats; D012701:Serotonin / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D000596:Amino Acids; D018377:Neurotransmitter Agents; D012701:Serotonin; D005680:gamma-Aminobutyric Acid; D005479:Flurazepam; D000109:Acetylcholine; D004298:Dopamine