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Biomedical subjects

E Manni

Publications and source records attributed to E Manni.

At least 37 records · Page 2Linked to original sources
PubMed1987

Influence of oculomotor nerve afferents on central endings of primary trigeminal fibers.

Painful fibers running in the third nerve and originating from the ophthalmic trigeminal area send their central projections at level of substantia gelatinosa of nucleus caudalis trigemini. The central endings of these fibers form axoaxonic synapses with trigeminal fibers entering the brain stem through the trigeminal root. The effect of electrical stimulation of the third nerve central stump on the central endings of trigeminal afferent fibers consists in an increased excitability, possibly resulting in a presynaptic inhibition. This inhibitory influence is due to both direct and indirect connections of the third nerve afferent fibers with the trigeminal ones.

Action Potentials↗
PubMed1987

Localization and somatotopy of sensory cells innervating the extraocular muscles of lamb, pig and cat. Histochemical and electrophysiological investigation.

The localization of sensory cells innervating the extraocular muscles (EOMs) was studied in the lamb, pig and cat in which horseradish peroxidase (HRP) was injected into each EOM. Electrophysiological techniques were also used to search for EOM stretch sensitive units in the semilunar ganglion. In lamb and pig labeling was observed in the semilunar ganglion only, while in cat labeled neurons were present in both the semilunar ganglion and mesencephalic trigeminal nucleus. In the semilunar ganglion of all these species a clear somatotopic organization of EOM afferents was observed. The histochemical somatotopic pattern of EOM afferents in the semilunar ganglion of lamb and pig was substantially in agreement with the electrophysiological arrangement. The responses recorded to EOM stretch in the semilunar ganglion of the pig were characterized by a low threshold and a slow adaptation as previously found in the lamb; on the contrary, in the semilunar ganglion of the cat only a few units were found, which showed high stretch threshold and quick adaptation.

Animals↗
PubMed1983

Localization of neurons innervating masticatory muscle spindle and periodontal receptors in the mesencephalic trigeminal nucleus and their reflex actions.

The mesencephalic trigeminal nucleus was studied in anaesthetized and curarized rabbits by recording the unitary activity through extracellular microelectrodes and identifying the constituent cell types. Two types of units were found, namely primary afferents supplying jaw raising muscle spindles and periodontal or gingival mechanoreceptors. These two groups of neurons exhibited a rostrocaudal somatotopy: the former occupied the entire rostral portion of the nucleus (A7-P2.3; trochlear decussation being taken as an arbitrary 0 level), the latter was located caudally (P3-P4.5) while the somata of both types of afferent fibres were present between P2.2 and P3. No evidence was found for representation of both tendon organs of jaw muscles and joint receptors. Among the units innervating muscle spindles, secondary afferents were largely more numerous than the primary ones. Among periodontal and gingival mechanoreceptor afferents, incisors were the most widely represented, followed by interalveolar gingiva and molars; the axonal conduction velocity ranged between 9 and 40 m/sec and between 8 and 16 m/sec for ipsilaterally and contralaterally projecting neurons, respectively. The motor responses obtained by electrical stimulation of discrete areas of the MTN confirmed the presence of a high degree of segregation between the two different populations of neurons. In fact, jaw raising movements are obtained when stimulating the area within A7 and P2 containing the somata of spindle afferent neurons, while only jaw opening movements are elicited by stimulation of the caudal levels of the nucleus. These data also show that the periodontal neurons whose somata are located in the MTN participate in the jaw opening reflex, just as the more numerous periodontal mechanoreceptors whose somata are located in the Gasser ganglion. Soma-somatic and soma-axon hillock gap junctions were found among the neurons of the MTN, particularly in the caudal third of the nucleus.

Animals↗
PubMed1980

Epileptogenic stimulation of the cortical masticatory area and the mesencephalic trigeminal nucleus.

1. The effects of epileptogenic stimulation of the cerebral masticatory area on the somata of the first-order neurons of masticatory proprioception localized in the mesencephalic trigeminal nucleus (MTN) were studied in curarized, lightly anaesthetized rabbits. 2. Low-frequency stimulations inducing modest cortical after-discharges fired the silent MTN units with latencies of 0.3-0.8 sec, and induced alternate excitatory and inhibitory effects on the active units. On some occasions the tonic afferent discharge was changed into rhythmic bursts, which occurred at the constant frequency of 2.5-3.5/sec for the entire range of stimulation frequencies used, i.e. from 0.3 to 10/sec. 3. High-frequency cortical stimulations eliciting true epileptic seizures induced a transient increase in discharge of the MTN units, followed by a prolonged inhibition. 4. All these effects were attributed to activation of reticular pathways acting on the some of the recorded proprioceptive neurons. Such a modulation of the proprioceptive input elicited by the epileptic masticatory cortex may contribute to the motor effects and to the changes of the masseteric reflex which occur during convulsive seizures.

Animals↗
PubMed1978

Afferent fibers and sensory ganglion cells within the oculomotor nerve in some mammals and man. II. Electrophysiological investigations.

The main aim of the present study was to localize with electrophysiological techniques the central projections and terminations of the aberrant trigeminal fibres contained in the oculomotor nerve of the lamb. After severing a trigeminal root, single-shock electrical stimulation of the trigeminal axons present in the central stump of the ipsilateral oculomotor nerve evoked field potentials in the area of, i) the subnucleus gelatinosus of the nucleus caudalis trigemini at the level of C1-C2; ii) the main sensory trigeminal nucleus; iii) the descending trigeminal nucleus and tract; iv) the adjacent reticular formation. Units whose discharge rate was influenced by such a stimulation were also found in the same territories. These regions actually exhibited degenerations after cutting an oculomotor nerve. We conclude, therefore, that the trigeminal fibres which leave the Vth nerve at the level of the cavernous sinus and enter the brain stem through the IIIrd nerve, end in the same structures which receive the terminations of the afferent fibres entering the brain stem through the sensory trigeminal root.

Afferent Pathways↗
PubMed1977

Somatotopic organization of the eye muscle representation in the semilunar ganglion.

A somatotopic arrangement of the extraocular muscle proprioception has been found in the semilunar ganglion. The cells innervating the proprioceptors of the superior rectus and superior oblique muscles lie more dorsally than those innervating the inferior rectus and inferior oblique. The lateral rectus and the medial rectus are represented in the lateral, respectively in the medial portion of the cellular pool which provides the sensitive innervation of the eye muscles.

Animals↗
PubMed1977

Reflex and reticular modulation of first-order proprioceptive neurons of the mesencephalic trigeminal nucleus.

Several investigations have shown that the vagus nerve and the reticular formation can affect the reflex responses of the masticatory muscles. The present research has been devoted to analyze the mechanism of such modulations of the masseteric reflex in the lamb. Extracellular records of the electrical activity of the mesencephalic trigeminal nucleus (MTN) was carried out in immobilized lambs by means of tungsten microelectrodes. Units were found which responded to lowering the jaw and to stretching the masseter muscle: they were identified as the first-order neurons of the masticatory proprioception on the basis of their electrophysiological properties. Single-shock or repetitive electrical stimulations of the cervical vagus nerve and of the bulbo-pontine reticular formation could affect the unitary discharge of the MTN: different patterns of activation and inhibition of the MTN units were seen; however, the activation was the most prominent effect. The responses did not depend upon the circulatory effects of the vagal stimulation. Thus the conclusion can be reached that the vagus and the reticular substance can modulate the masseteric reflex at level of the perikarya of the afferent pathway. Such a statement is supported also by the presence of synaptic boutons on the soma of the MTN neurons.

Action Potentials↗