TOPOGRAPHIC IDENTIFICATION OF THE PONTOMEDULLARY RESPIRATORI-SENSITIVE NUCLEI OF THE RAT BRAIN BY GLUTAMATE MICRO-STIMULATIONS

Abstract

Automatic control of breathing is highly dependent on the integrity of the pontomedullary network of reciprocally connected neurons localized in a number of functionally and neurochemically different compartments. Glutamate is considered the key neurotransmitter mediating signal transmission in the respiratory regions of the brainstem. Identification of the respiratory-sensitive neurons using this neurotransmitter for microstimulations provides an insight into the topographic organization of the pontomedullary nuclei involved in the modulation and control of breathing.Three types of respiratory responses were observed following glutamate microinjections: hyperpnea, apneusis (inspiratory cramp) and hypopnea or apnea. Hyperpnea was obtained as a result of microstimulations in the region of lateral parabrachium and caudal Kölliker-Fuse nuclei. Apneustic response was observed in the region localized ventrally from superior cerebellar peduncle, while hypopneic or apneic responses followed glutamate microinjections in the region of ventral Kölliker-Fuse nucleus and a narrow area between motor and principal sensory trigeminal nucleus, which is referred to as intertrigeminal region.Anatomical distribution of the obtained respiratory responses depends on the localization of microinjections and ascendant and descendent projections stemming from the sites of stimulation.

Keywords

• glutamate
• pontomedullary region of the rat brain
• microstimulation
• breathing