[A case of the late complication of stapedoplasty].

The authors report a case of the late complication of stapedoplasty that developed 1.5 years after the otherwise successful surgical intervention. Computed tomography revealed the displacement of the stapedial prosthesis into the internal ear.

[The neurochemical mechanisms of the inhibitory influences of stimulation of the central gray substance on the high-threshold reflex activity of the reticular formation].

Influences of bulbar microinjections of some neuromodulator antagonists (methysergide, haloperidol, naloxone) on depression dynamics of spino-bulbo-spinal (SBS) reflex from the periaqueductal grey (PAG) stimulation were studied in chloralose anesthetized rats. Microinjections were made into the reticular gigantocellular nucleus which is a main supraspinal centre of SBS reflexes. It is found that methysergide administration (10(-5) mol/l) causes a considerable (two to four times as less) decrease of SBS-reflex depression evoked by PAG stimulation by a short high-frequency series of stimuli.

[The effect of the joint stimulation of the central grey substance and substantia nigra on the low- and high-threshold startle reflexes in anesthetized rats].

Influences of separate and combined stimulation of the periaqueductal grey matter (PAG) and the substantia nigra (SN) on startle reflexes were studied in chloralose-anesthetized rats; the reflexes were low-threshold, tactile ones and high-threshold, spino-bulbo-spinal (SBS) ones. A clear interaction between effects of the PAG and SN stimuli occurred by combination of these stimulations was found. The interactions were exhibited with potentiation or diminution of influences evoked by separate stimuli depending on type of reflexes investigated and sorts of influences as well as on sequences of stimulations.

[Influence of stimulation of the central gray matter on low- and high-threshold startle reflexes].

Influences of the periaqueductal gray matter (PAG) stimulation on high-threshold jaw opening reflex (JOR) evoked by tooth pulp stimulation and on two functional types of startle reflexes were studied in chloralose anesthetized cats; the startle reflexes were high-threshold ones evoked by intense peripheral nerve stimulation (spino-bulbo-spinal, SBS, reflex) and low-threshold ones evoked by tactile stimuli (tactile spino-reticulo-spinal, TSRS, reflex). Stimulation of the majority of PAG sites induced considerable inhibition of JOR as well as profound depression of SBS-reflexes and moderate depression of TSRS-reflexes. Some PAG sites were found to exert a facilitatory action on the latter reflex.

[The effect of stimulation of the substantia nigra on the low- and high-threshold neuronal responses of the reticular formation].

Modulation of somatosensory responses of bulbar (n. reticularis gigantocellularis) and pontine (n. reticularis pontis caudalis) reticular neurons by the substantia nigra (SN) stimulation was studied in cats under light chloralose anesthesia.

[The effect of stimulation of the substantia nigra on low- and high-threshold startle reflexes in the cat].

Effects of the substantia nigra (pars compacta) stimulation on two functional types of startle reflexes were studied in chloralose-anesthetized cats. The reflexes were the low-threshold ones evoked by tactile stimuli (T-reflex) and high-threshold ones evoked by intense peripheral nerve stimulation (spino-bulbo-spinal, SBS reflex). It was found that substantia nigra stimulation exerted mainly inhibitory influences on both types of reflexes.

[Effect of stimulation of the central gray substance on the low- and high-threshold responses of the reticular neurons in the pons and medulla oblongata].

The modulation of somatosensory responses of bulbar (n. reticularis gigantocellularis) and pontine (n. reticularis pontis caudalis) reticular neurons by electrical stimulation of periaqueductal gray matter (PGM) was studied in cats under light chloralose anaesthesia.

[Respiratory modulation of startle reflexes in the cat].

Phasic respiratory influences on late reflex discharges in the limb and lower intercostal nerves--electrophysiological analogs of somesthetic and acoustic startle reflexes (SR)--were studied in unanesthetized (decerebrated) or chloralose-anesthetized cats. The integrated values of the SR in both types of nerves always essentially decreased during inspiratory phase (by 28-58% on the whole) compared to those during expiratory phase. Data obtained evidence that this respiratory modulation of the SR occurs mainly at the brainstem level.

[Features of activation of reticulospinal neurons of the pons and medulla oblongata of the cat by somatosensory stimuli of different modalities].

Response of reticulo-spinal (RS) neurons in two reticular structures (n. reticularis pontis caudalis and n. reticularis gigantocellularis) to electrical nerve stimulation and natural mechanical non-nociceptive (tapping) and nociceptive (pinch and prick) stimuli were studied in chloralose-anesthetized cats.

[Reticular structures of the cat brain participating in startle reflexes in response to somatic stimuli of different modalities].

Characteristics and reticular mechanisms of two types of late reflex responses (equivalents of the startle reflex) evoked by weak (tactile stimuli) and strong (high-threshold peripheral nerve stimulation) stimulations were studied in chloralose-anesthetized cats; these responses were designated as "tactile" (T) and "spino-bulbo-spinal" (SBS) reflexes, respectively. Some differences in the peripheral and central (brainstem) organization of these reflexes were found. In particular, the existence of the rostro-caudal differentiation of reticular structures involved in these types of reflexes was revealed using differential lesions of the brainstem reticular formation as well as its pharmacologic blockades (by means of microinjections of sodium chloride or procaine); the T-reflex was found to relay mainly through the pontine RF level, while the SBS-reflex--predominantly through the bulbar RF.

[Features of the activation of neurons of the reticular formation of the brain stem in the cat to somatic stimuli of various modality].

Neuronal responses of two reticular structures--nucleus reticularis pontis caudalis (RPC) and nucleus reticularis gigantocellularis (RGC)--to electrical nociceptive stimulation of the internal intercostal nerve and non-nociceptive, tactile stimulation of the skin in the same somatic area have been studied in chloralose anesthetized cats. It was shown that the mean number of action potentials in responses of RPC-neurons to tactile stimulation exceeded that for FGC-neurons by 20-150%. On the opposite, the average number of action potentials in RPC-neurons in response to nerve stimulation was lower by 15-54% than those of bulbar neurons.

[Effect of bulbar microinjections of noradrenaline, isoproterenol and phentolamine on the spino-bulbo-spinal reflex in the cat].

In chloralose-anesthetized cats a long lasting depression of spino-bulbo-spinal (SBS) reflex discharges following microinjections of noradrenaline and its agonist (isoproterenol) in the medial bulbar reticular formation was revealed. Microinjections of phentolamine (alpha-adrenoceptor antagonist) were followed by prominent enhancement of SBS-reflexes. Depressive action of the locus coeruleus stimulation on SBS-responses essentially decreased after these microinjections.

[Reticular neurons with double axon projections: participation in execution of the reflex startle response in the cat].

Synaptic processes in the bulbar and pontine reticular neurons with mixed ascending descending axon projections were studied on chloralose-anesthetized cats during startle reaction to somatic stimulation (spino-bulbo-spinal reflex). Characteristics of these processes proved to be similar to those reported for genuine reticulospinal neurons. Evidence was obtained that as in case of reticulospinal neurons, about a half of the investigated cells were simultaneously involved in suprasegmental relay of the spino-bulbo-spinal reflexes.

[Synaptic excitation of reticulospinal neurons during the startle reaction in cats anesthetized with chloralose].

Synaptic processes in the bulbar and pontine reticulospinal neurons (RS-neurons) were studied in chloralose-anesthetized cats during startle reaction to somatic stimulation ("spino-bulbo-spinal"--SBS-reflex). Excitatory PSPs were found to be a main type of synaptic responses in the RS-neurons; they were oligosynaptic (including monosynaptic) and polysynaptic. The comparison between synaptic responses of RS-neurons and SBS-reflexes showed that the polysynaptic EPSPs were most effective in generation of a SBS descending volley.