Biomaterial Database

Modulation of vestibulospinal reflexes through microinjection of GABAergic agents in the dorsal pontine tegmentum of decerebrate cats. 1995

O Pompeiano, and M Ioffe, and P Andre

Dipartimento di Fisiologia e Biochimica, Università di Pisa, Italy.

1. The locus coeruleus (LC) neurons control posture as well as the gain of the vestibulospinal (VS) reflexes either through direct coeruleospinal (CS) projections or by inhibiting the dorsal pontine reticular formation (pRF) and the related medullary inhibitory reticulospinal (RS) systems. After the demonstration that the LC neurons are under the inhibitory control of GABAergic afferents, experiments were performed to investigate whether the same system could also suppress the activity of the dorsal pRF, thus intervening in the control of posture and VS reflexes. 2. In precollicular decerebrate cats, unilateral microinjection into the dorsal pRF of the GABA-A antagonist bicuculline or the GABA-B antagonist faclofen (0.13-0.25 microliter at 2.5 micrograms/microliter saline) decreased the tonic contraction of the ipsilateral triceps brachii, but greatly increased the amplitude of the EMG responses of the same muscle to roll tilt of the animal (at 0.15 Hz, +/- 10 degrees). This increase in gain of the VS reflexes was not associated with great changes in phase angle of the responses, which were always characterized by an increased EMG activity during ipsilateral tilt and a decreased activity during contralateral tilt. The same injection also produced in some instances a slight decrease of the extensor tonus of the contralateral forelimb, associated with a moderate increase in the amplitude of modulation and thus in the response gain of contralateral triceps brachii to labyrinth stimulation. However, when the ipsilateral effects were prominent, the response gain of the contralateral triceps muscle was slightly depressed, while the pattern of response reversed. 3. The changes in posture and reflexes described above appeared 5-10 min after unilateral injection of the GABA antagonists in the pRF, reached the highest values in about 30 min and fully recovered to the control levels within 2 h after the injection. These effects were not due to irritative phenomena following injection of the fluid, since neither changes in posture nor in the response gain of the triceps brachii to labyrinth stimulation were observed after injection of an equal volume of vehicle in the pRF of that side. On the other hand, an increase in postural activity associated with a decrease in the response gain of the ipsilateral and contralateral triceps brachii to animal tilt was observed after unilateral microinjection into the dorsal pRF of GABA agonists. 4. Histological controls indicated that the structure responsible for the postural and reflex changes was located in the dorsal pontine reticular formation, ventral to the LC.(ABSTRACT TRUNCATED AT 400 WORDS)

UI	MeSH Term	Description	Entries
D007758	Ear, Inner	The essential part of the hearing organ consists of two labyrinthine compartments: the bony labyrinthine and the membranous labyrinth. The bony labyrinth is a complex of three interconnecting cavities or spaces (COCHLEA; VESTIBULAR LABYRINTH; and SEMICIRCULAR CANALS) in the TEMPORAL BONE. Within the bony labyrinth lies the membranous labyrinth which is a complex of sacs and tubules (COCHLEAR DUCT; SACCULE AND UTRICLE; and SEMICIRCULAR DUCTS) forming a continuous space enclosed by EPITHELIUM and connective tissue. These spaces are filled with LABYRINTHINE FLUIDS of various compositions.	Labyrinth,Bony Labyrinth,Ear, Internal,Inner Ear,Membranous Labyrinth,Bony Labyrinths,Ears, Inner,Ears, Internal,Inner Ears,Internal Ear,Internal Ears,Labyrinth, Bony,Labyrinth, Membranous,Labyrinths,Labyrinths, Bony,Labyrinths, Membranous,Membranous Labyrinths
D007839	Functional Laterality	Behavioral manifestations of cerebral dominance in which there is preferential use and superior functioning of either the left or the right side, as in the preferred use of the right hand or right foot.	Ambidexterity,Behavioral Laterality,Handedness,Laterality of Motor Control,Mirror Writing,Laterality, Behavioral,Laterality, Functional,Mirror Writings,Motor Control Laterality,Writing, Mirror,Writings, Mirror
D008845	Microinjections	The injection of very small amounts of fluid, often with the aid of a microscope and microsyringes.	Microinjection
D011149	Pons	The front part of the hindbrain (RHOMBENCEPHALON) that lies between the MEDULLA and the midbrain (MESENCEPHALON) ventral to the cerebellum. It is composed of two parts, the dorsal and the ventral. The pons serves as a relay station for neural pathways between the CEREBELLUM to the CEREBRUM.	Pons Varolii,Ponte,Pons Varolius,Pontes,Varolii, Pons,Varolius, Pons
D011187	Posture	The position or physical attitude of the body.	Postures
D012018	Reflex	An involuntary movement or exercise of function in a part, excited in response to a stimulus applied to the periphery and transmitted to the brain or spinal cord.
D002415	Cats	The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)	Felis catus,Felis domesticus,Domestic Cats,Felis domestica,Felis sylvestris catus,Cat,Cat, Domestic,Cats, Domestic,Domestic Cat
D003655	Decerebrate State	A condition characterized by abnormal posturing of the limbs that is associated with injury to the brainstem. This may occur as a clinical manifestation or induced experimentally in animals. The extensor reflexes are exaggerated leading to rigid extension of the limbs accompanied by hyperreflexia and opisthotonus. This condition is usually caused by lesions which occur in the region of the brainstem that lies between the red nuclei and the vestibular nuclei. In contrast, decorticate rigidity is characterized by flexion of the elbows and wrists with extension of the legs and feet. The causative lesion for this condition is located above the red nuclei and usually consists of diffuse cerebral damage. (From Adams et al., Principles of Neurology, 6th ed, p358)	Decerebrate Posturing,Decorticate Rigidity,Decorticate State,Rigidity, Decerebrate,Rigidity, Decorticate,Decerebrate Posturings,Decerebrate Rigidity,Decerebrate States,Decorticate Rigidities,Decorticate States,Posturing, Decerebrate,Posturings, Decerebrate,Rigidities, Decorticate,State, Decerebrate,States, Decerebrate
D004576	Electromyography	Recording of the changes in electric potential of muscle by means of surface or needle electrodes.	Electromyogram,Surface Electromyography,Electromyograms,Electromyographies,Electromyographies, Surface,Electromyography, Surface,Surface Electromyographies
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia