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At least 37 records · Page 2Linked to original sources
PubMedDate not supplied

Varied influence of damage to the motor cortex on precision avoidance and escape reactions in dogs.

The influence of local extirpation of the representation of the forelimb in the motor area of the cortex on the performance of precision elevations of this limb was investigated. Even imprecise avoidance reactions to an acoustic signal did not recover spontaneously. Irregular motoric reactions which were insufficient in amplitude could easily be restored in the course of retraining, but precise movements (both rapid fused, as well as relatively slow stepwise movements) did not recover for at least a half year after the operation. By contrast with this, precise rapid reactions in response to electrical stimulation of a "working" limb (inducing unconditioned reflex flexion) remained essentially preserved, i.e., the capacity to stop the movement in the correct (previously learned) position of the limb was preserved. The capacity to fix the position of the raised limb was not lost, but was persistently impaired. The capacity to overcome the unconditioned reflex flexion during the performance of extensor "slow" escape reaction was reduced sharply and persistently. Limb presentation reactions regulated by vision were essentially spontaneously and nearly completely restored within a month.

Acoustic Stimulation↗
PubMedDate not supplied

[An experimental unit for the recording of the escape reaction of a ground snail to tactile stimulation].

An original working experimental unit for noninvasive objective recording of the magnitude of escape reaction of a ground snail evoked by tactile stimulation is described. A. snail creeps upwards over the cylinder rotating around its horizontal axis. A watching device ensures a constant snail position relative to a light source and a photoelement. A device for tactile stimulation which provides graduated energy of an impact is constructed on the basis of the magnetic circuit of a loudspeaker. In response to a tactile stimulus a snail pulls in its feelers, head, and foot, and the area of snail's shadow decreases. These changes are indicated by the photoelement.

Animals↗
PubMed1997

The mechanism of action of alpha 2 adrenoceptor blockers as revealed by effects on open field locomotion and escape reactions in the shuttle-box.

The precise mechanism of action of alpha 2 adrenoceptor blockers in not known, although in principle they have two main effects: (i) they stimulate the norepinephrinergic system by inhibiting the negative feed back of norepinephrine release (presynaptic effect) and (ii) they inhibit the effects of norepinephrine on postsynaptic alpha 2 adrenoceptors. We postulate that if the presynaptic actions of the antagonists prevail, the enhanced norepinephrine release leads to an activation of postsynaptic alpha 1 or beta adrenoceptors. In this case the effects of alpha 2 adrenoceptor blockers can be reversed by antagonists acting on the latter two adrenoceptors, since postsynaptic alpha 2 adrenoceptors are also blocked. If the postsynaptic blockade of alpha 2 adrenoceptors is the main cause of effects, than the blockade of alpha 1 or beta adrenoceptors should not reverse the action of alpha 2 blockers. The alpha 2 blocker idazoxan (dose 0.5-5 mg/kg) increased locomotor activity in an open field, an effect that was abolished by both alpha 1 and beta receptor blockers (prazosin and propranolol, respectively). Escape responses in a shuttle box were strongly suppressed by idazoxan (0.5-2 mg/kg). However, this effect was not changed by concomitant alpha 1 or beta receptor blockade. These results suggest that the mechanism of action of alpha 2 adrenoceptor blockers depends on which effects are studied. Exploration seems to be affected by a presynaptic mechanism as neurons bearing postsynaptic alpha 1 or beta adrenoceptors are involved in the control of this behavior, while escape reactions appear to be affected by the postsynaptic blockade of alpha 2 adrenoceptors (i.e. neurons bearing postsynaptic alpha 2 adrenoceptors are involved in its control). Thus, there is no generalized mechanism of action for alpha 2 adrenoceptor blockers; their precise mode of action should be investigated in each particular case.

Adrenergic alpha-2 Receptor Antagonists↗
PubMedDate not supplied

[The functional role of the motor area of the cortex in the acquisition of escape reactions in dogs].

The model of escape conditioning similar to classical (pavlovian) was proposed. During shock application to the hind limb (a conditioned stimulus) the ipsilateral foreleg flexion was elicited by a stimulation of the motor cortex (an unconditioned stimulus); both stimuli were turned off in the course of the forepaw lifting. Such uniform pairings resulted in elaboration of a reaction of the foreleg flexion in response to the shock. Prolonging the shock by 3 s after the cortical stimulation led to a rapid extinction of the acquired response. So a possibility to instrumentalize movements elicited by stimulation of the motor cortex (MI) was proved. This is in argument in favour of an assumption that the established "instrumental" connection (drive-motor structures) can be addressed directly to the motor cortex.

Animals↗
PubMedDate not supplied

[A reversible functional disorder of the escape reaction as a model for studying the effect of tranquilizers].

A model of reversible functional disorders of the escape response (ER) for studying the effect of tranquilizers is proposed. The model is based on the unexpected action of electric current used regardless of the specific relation (stimulus-response effect). This results in enhanced emotional stress, reduces ER, and increases intersignal responses. The model proposed has less in common with the conflict situation because no interference of the opposite motivations is suggested, namely, the formation and disturbance of ER is based on the same unconditioned stimulus and test performance does not suggest punishment with electric current. We found that hydazepam (20 mg/kg) prevents and phenazepam (0.1 mg/kg) reduces the ER disorders.

Animals↗
PubMed1992

Cholinergic transmission at the first synapse of the circuit mediating the crayfish lateral giant escape reaction.

1. The chemical synapses between mechanoreceptor neurons and first-order interneurons in the lateral giant (LG) neuron escape circuit of the crayfish have plastic properties, some of which are believed to be the basis for behavioral habituation and sensitization. In this investigation pharmacological experiments were conducted to assess the role of cholinergic synaptic transmission in this pathway. 2. Arterial perfusion of the cholinergic agonist carbachol produced increased activity of many abdominal nerve cord units, including an identified first-order interneuron (interneuron A) in the LG circuit. A general increase in activity of interneurons in this circuit in the presence of certain cholinergic agonists was inferred from an increase in the frequency of occurrence of spontaneous excitatory postsynaptic potentials (EPSPs) recorded in the LG. 3. Cholinergic antagonists reduced the amplitude of spontaneous and evoked sensory neuron-to-interneuron A EPSPs and decreased the disynaptic (via 1st-order interneurons) component of evoked EPSPs in the LG. These effects indicate that postsynaptic cholinergic receptors are utilized in mechanosensory synaptic transmission to the first-order interneurons of this circuit. The relative potencies of the blockers tested (mecamylamine > picrotoxin >>> curare > atropine) suggest that the receptors on the interneurons belong to a previously characterized class of crustacean cholinergic receptors that resemble the ganglionic nicotinic subtype of vertebrates. 4. Nicotinic agonists (carbachol, tetramethylammonium hydroxide, 1,1-dimethyl-4-phenyl-piperazium iodide) produced depolarizing (decreased input resistance) responses on the LG neuron itself. These responses persisted during blockade of chemical transmission by cobalt. The presence of cholinergic receptors on the LG, a cell in which all known inputs mediating sensory excitation are electrical, is discussed. 5. Application of muscarinic agonists (pilocarpine, oxotremorine) resulted in a long-lasting reduction of the evoked sensory neuron-to-interneuron A EPSP and the disynaptic component of the evoked EPSP in the LG. No effects on the membrane potential or input resistance of the interneurons were detected. It is proposed that presynaptic receptors with a muscarinic profile are present on mechanosensory neurons and that these receptors mediate a reduction of transmitter release.

Acetylcholine↗
PubMed1998

[Escape reactions and variation in some genetic parameters in larva from the malaria mosquito Anopheles messeae].

The relationship between the escape response and four types of variations--inversion polymorphism, the number of denses in the stigmal plate ridges, their asymmetry, and stripe-nonstripe variation--was studied in larvae of malaria mosquito Anopheles messeae Fall. from natural populations. Pigmented individuals were shown to have a more reduced responce than nonpigmented ones. Asymmetry declined in the direction from unresponsive larvae to those repeatedly (responded). Number of denses was lower in larvae that responded once and higher in those with repeated response. In the latter, variation of this characteristic decreased substantially. The relation of the escape response to inversion polymorphism was most complicated. Larvae that responded a single time did not differe from unresponsive larvae in their chromosomal composition. Among larvae that responded twice, the proportion of heterozygotes 2R01 and 3L01, female XL11, and inversion XL2 increased, and the proportion of female XL01 decreased. Larvae of Anopheles beklemishevi were found to be less responsive than those of A. messeae. The responsiveness of A. messeae is mainly due to heterozygosity.

Animals↗