Glutamatergic-cholinergic synergistic interaction in the pontine reticular formation. Effects on catalepsy

Abstract

Microinjections of small amounts of the cholinergic receptor agonists carbachol and nicotine into the pontine reticular formation (PRF) of rats were shown to induce catalepsy. Catalepsy was used in this work as an experimental model for studying the interactions between cholinergic mechanisms and excitatory amino acid mechanisms in the PRF. The excitatory amino acid (EAA) receptor agonists glutamate, NMDA, kainate and AMPA were microinjected in subcataleptic doses before carbachol in the same location into the PRF. All the EAA receptor agonists injected induced a significant potentiation of the cataleptogenic effect of carbachol. The NMDA receptor antagonist MK-801 and the non-NMDA receptor antagonist DNQX microinjected in picomol doses before the EAA receptor agonists attenuated their potentiating effect. These results support the suggestion that EAA neuronal mechanisms contribute synergistically with the cholinergic mechanisms to the PRF neuronal interactions involved in the generation of catalepsy. Similar synergistic interactions might be active in the generation of other pontine behavioral manifestations like REM sleep.

Neuropharmacology of Sleep and Wakefulness

“…140 Glutamate elicits excitatory responses from pontine reticular formation neurons, 141, 142 and glutamatergic and cholinergic transmission in the pontine reticular formation interact synergistically to potentiate catalepsy. 143 Given individually, agonists for AMPA, kainate, and NMDA receptors evoke excitatory responses from pontine reticular formation neurons. 133 Dialysis delivery of the NMDA receptor antagonists ketamine or MK-801 to cat pontine reticular formation decreases acetylcholine release in the pontine reticular formation and disrupts breathing.…”

Neuropharmacology of Sleep and Wakefulness

“…Glutamatergic neurons are present in rat pontine reticular formation125 and neurons in the pontine reticular formation are capable of synthesizing glutamate for use as a neurotransmitter 126. Glutamate elicits excitatory responses from pontine reticular formation neurons,127, 128 and glutamatergic and cholinergic transmission in the pontine reticular formation interact synergistically to potentiate catalepsy 129. Given individually, agonists for AMPA, kainate, and NMDA receptors evoke excitatory responses from pontine reticular formation neurons 121.…”