ABSTRACT
In adult anaesthetized rats the respiratory reactions to microinjections of GABA (10(-5) M) and baclofen (10(-6) M) into Botzinger complex (BC) and pre-Botzinger complex (PBC) were investigated. It was shown, that GABA microinjections into BC shortened inspiratory time and extended expiratory time while respiratory rate was not changed essentially, under this conditions the tidal volume and ventilation were increased. GABA microinjections into PBC significantly inhibited respiratory rhythm due to inspiratory and expiratory time prolongations and reduced tidal volume. The microinjections of baclofen into BC reduced expiration time and ventilation, and increased respiratory frequency whereas microinjections into PBC increased tidal volume without respiratory rate and expiratory time changes. It is suggested that the reactions observed demonstrate the various contribution of GABAergic mechanisms, including GABA(B)-receptors within BC and PBC, in control of respiratory pattern parameters.
Subject(s)
Baclofen/administration & dosage , Medulla Oblongata/drug effects , Muscle Relaxants, Central/administration & dosage , gamma-Aminobutyric Acid/administration & dosage , Animals , Exhalation/drug effects , Exhalation/physiology , Female , Inhalation/drug effects , Inhalation/physiology , Male , Medulla Oblongata/physiology , Microinjections , Rats , Respiratory Rate/drug effects , Respiratory Rate/physiology , Tidal Volume/drug effects , Tidal Volume/physiologyABSTRACT
Unilateral microinjections of acetylcholine into the rat solitary tract nucleus evoked inhibitory effects in electrical activity of symmetrical portions of the diaphragm and external intercostal muscles. Administration of propranolol exerted excitatory respiratory responses. The findings suggest participation of cholin- and noradrenergic systems in inhibitory mechanisms of respiratory control. Different roles of the right and left solitary tract nuclei in their involvement in formation of efferent impulses to bilateral inspiratory muscles, are discussed.
Subject(s)
Acetylcholine/physiology , Adrenergic beta-Antagonists/pharmacology , Norepinephrine/physiology , Propranolol/pharmacology , Respiratory Muscles/physiology , Solitary Nucleus/physiology , Acetylcholine/pharmacology , Animals , Efferent Pathways/physiology , Electromyography , Functional Laterality/physiology , Microinjections , Motor Neurons/physiology , Rats , Respiratory Muscles/drug effects , Respiratory Muscles/innervation , Solitary Nucleus/drug effectsABSTRACT
The asymmetrical reactions of respiratory neurons of the right and left halves of the respiratory center and varied changes in bioelectrical activity of external intercostal muscles on both sides of the chest were discovered in experiments on anesthetized cats in response to successive electrical stimulation of the symmetrical cortical areas of the right and left cerebral hemispheres before and after callosotomy. It was demonstrated that callosotomy increased on both sides of the respiratory center the quantity of neurons responsive to ipsilateral cortical stimulation and determined the character of the asymmetrical reactions of right and left respiratory neurons and intercostal muscles. On the basis of the data obtained it is concluded that the corpus callosum contributes to the functional integration of both halves of the respiratory center.
