Oral pathology quiz #51. Case number 2. Mucus escape reaction or "mucocele".
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The effects of intraperitoneal injections of increasing doses of apomorphine, clonidine or 5-methoxy-NN-dimethyltryptamine (5-m-DMT) on approach and escape reactions induced by lateral hypothalamic (LH) or mesencephalic central gray (CG) stimulation were compared in BALB/c and DBA/2 mice. Apomorphine increased both the approach latency for LH stimulation and the escape latency for CG stimulation; the BALB/c strain was more reactive than DBA/2 animals. Clonidine reduced the approach latency for LH stimulation only in the BALB/c strain. 5-m-DMT increased escape latency both for LH and CG stimulation only in the DBA/2 strain. These results suggest that the neurochemical regulation of escape reactions respectively generated by LH or CG activation is partially different: dopamine seems to be involved only in CG aversion, whereas serotonin (5-HT) modulates both LH and CG escape reactions. Moreover, our results demonstrate a noradrenergic influence on the appetitive component of LH stimulation. Finally, they confirm that approach and escape reactions, particularly when induced from lateral hypothalamus, depend on distinct neuronal populations.
RATIONALE: Escape reactions induced by electrical stimulation of the dorsolateral periaqueductal gray (dlPAG) are inhibited by local administration of benzodiazepine (BZ) or serotonin (5-HT) receptor agonists. Nitric oxide (NO) is a gas messenger that may mediate aversive behaviors. NO donors injected into the dlPAG induce escape reactions. OBJECTIVES: To test the hypothesis that the escape reactions induced by a NO donor in the dlPAG would be attenuated by pre-treatment with BZ-receptor or 5-HT-receptor agonists. METHODS: Male Wistar rats with cannulae aimed at the dlPAG received microinjections of vehicle (0.2 microl), the BZ midazolam maleate (80 nmol), the 5-HT(1A)-receptor agonist 8-OH-DPAT (8 nmol or 16 nmol) or the 5-HT(2A/2C)-receptor agonist DOI (16 nmol) 10 min before the administration of the NO donor SIN-1 (150 nmol). Behavioral observation took place immediately after the last injection in an open arena over a 10-min period. RESULTS: SIN-1 induced escape reactions characterized by running and jumps. Pre-treatment with DOI, but not 8-OH-DPAT, partially inhibited the effects of SIN-1. Pre-treatment with midazolam maleate, however, completely prevented the effects of the NO donor. CONCLUSION: The results suggest that the aversive-like effects of NO donor in the dlPAG may be modulated by the BZ and 5-HT(2A/2C) receptors.
Food and escape reactions of Nereis virens to oscillations of a ball 2 mm in diameter in water have been studied. These antagonistic reactions differ significantly by the range of ball oscillations which evoked them. The range from 10 to 30 Hz appeared to be optimal for food reaction, and the range above 40 Hz -- for escape reaction. Worms are able to detect a ball from a distance of 12--13 mm at optimal oscillation frequency 30 Hz. Possible receptor mechanisms providing these types of reaction are discussed.
Whole-body shortening was studied in the leech, Hirudo medicinalis, by a combination of videomicroscopy and multielectrode recordings. Video microscopy was used to monitor the animal behavior and muscle contraction. Eight suction pipettes were used to obtain simultaneous electrical recordings from fine roots emerging from ganglia. This vital escape reaction was rather reproducible. The coefficient of variation of the animal contraction during whole-body shortening was between 0.2 and 0.3. The great majority of all leech longitudinal motoneurons were activated during this escape reaction, in particular motoneurons 3, 4, 5, 8, 107, 108, and L. The firing pattern of all these motoneurons was poorly reproducible from trial to trial, and the coefficient of variation of their firing varied between 0.3 and 1.5 for different motoneurons. The electrical activity of pairs of coactivated motoneurons did not show any sign of correlation over a time window of 100 ms. Only the left and right motoneurons L in the same ganglion had a correlated firing pattern, resulting from their strong electrical coupling. As a consequence of the low correlation between coactivated motoneurons, the global electrical activity during whole-body shortening became reproducible with a coefficient of variation below 0.3 during maximal contraction. These results indicate that whole-body shortening is mediated by the coactivation of a large fraction of all leech motoneurons, i.e., it is a distributed process, and that coactivated motoneurons exhibit a significant statistical independence. Probably due to this statistical independence this vital escape reaction is smooth and reproducible.
Mice of the inbred strain DBA/2, when exposed to a social conflict, developed a low intensity, naloxone-insensitive analgesia after 15 bites, and a more pronounced naloxone-sensitive analgesia after 45 bites. The effective inhibition of the antinociceptive response following low and high number of bites by the alkylating opiate antagonist beta-chlornaltrexamine suggests participation of opioid mechanisms at both stress levels. Emergence of an increased tail-flick latency was indicated by the occurrence of defensive upright postures upon contact with the opponent, while animals displaying full analgesic response during the period of bite 31-45 increased their escape reactions without being in contact with the aggressor. Suppression of social conflict analgesia in mice by pretreatment with opiate antagonists facilitated the occurrence of these escape reactions. The display of panic escape responses is discussed in the context of increased fear and helplessness that developed under conditions of sustained attacks.
In experiments on two dogs it has been found that testing electric stimulation of the lateral hypothalamus reproduces instrumental movement in case of elaborated alimentary instrumental conditioned reflexes (CR) to a tone and does not reproduce it at elaborated acid-defensive instrumental CR. Under testing electric stimulation of the medial hypothalamus the instrumental movement practically is not reproduced neither in alimentary nor in defensive situation. Appearance of instrumental movement at LH electro-stimulation in alimentary situation is connected with activation of backward conditioned connection from motivation "alimentary" LH centre to representation of this movement in the motor cortex.
After a lesion of serotoninergic neurons performed by administration of 5.7-dihydroxytriptamine into the dorsal raphe nucleus, effects of neurotensin microinjections into the substantia nigra on rat behavior were investigated. Serotoninergic lesions resulted in enhanced fear of rats manifested as an increase in the number of intersignal avoidance reactions and intensification of escape reactions. Neurotensin microinjections into the substantia nigra diminished the neurotoxin action thus increasing the adaptive character of defensive behavior of rats with deficit of functions of serotonin neurons.
We studied influence of protein synthesis inhibitors on short-term sensitization of Helix escape reaction and potentiation cholinosensitivity in command neurons. Inhibitor of protein synthesis anisomycin does not prevent behavioral sensitization. Anisomycin and irreversible inhibitor of protein synthesis saporin change the dynamics of cholinosensitivity potentiation in command neurons. The results Suggest that investigated sensitization of Helix escape reaction does not require synthesis of new proteins.
The extirpation of the foreleg area in the somatosensory cortex (SI) in dogs was performed in order to study the role of this area in motor control of the corresponding limb. Stable precise avoidance and escape reactions were established before the cortical lesion. Avoidance reactions disappeared during the first week after the surgery but then they were gradually restored without retraining. At the third weak there was a practically complete recovery of the precision of movements, the ability to fix the leg position and of the duration of successive phases of the reactions. The conclusion was drawn that the initial disturbances of avoidance reactions were most likely the result of diaschisis (shock). The initial disturbances of visually guided instrumental movements and escape reactions were much weaker than those of avoidance reactions (lifting of the foreleg in response to conditioned signal).
The effect of transection of the descending root of the spinal trigeminal tract on nociceptive and aversive reactions evoked by stimulation of the tooth pulp nerve was studied in cats. The transection was performed 1-1.5 mm caudally to the obex. 1. The nociceptive reaction, characterized by wide opening of the jaw, dorsiflexion and rotation of the head and by signs of affective behaviour, remained unchanged after transection of the descending root of the trigeminal nerve (n = 6). 2. The instrumental escape reaction was elaborated in three cats before transection of the descending root of the trigeminal nerve and in three cats after transection. The escape reaction was retained after transection of the descending root and the speed of learning to escape the tooth pulp stimulation did not significantly differ in these two groups of animals. 3. It is to be concluded that the transection of the descending root of the spinal trigeminal tract in the cat does not result in dental analgesia.
Dogs of 1.5 and 7 months and rats of 15, 20, 30, 45, 60, 80, and 100 days of age were given acquisition training in an escape task. The previous observations suggested that difficulties in defensive conditioning typically found in young animals were connected with their generalized perception of Igarning conditions. To facilitate the discrimination of the environmental factors a conditioned signal was not applied and the home cage was used as a "safe" compartment. The intertrial intervals were increased up to 2 hours for dogs and 24 hours for rats. Under such conditions an acquisition of escape reaction was most rapid in animals of early age. The period of effective learning (exaltation) in rats began from 20 and lasted to 60 days of age, the maximal efficiency being observed at 20 days. Pups of 1.5 months had learned more quickly than those of 7 months of age. Variations of learning efficiency in ontogeny of rats were positively correlated with changes of correct escape reaction search activity. Phenomenon of learning exaltation in ontogeny was supposed to be connected with the high level of activity of perception and association cerebral mechanisms being the result of immaturity of inhibitory structures.
The effect of nootropics on the retrograde amnesia induced by electroshock was studied on a model of the active conditioned escape reaction (pole jumping). In untreated animals the daily application of electroshock for three days, immediately after the training, led to a significant retardation of the development of a conditioned escape reaction. The administration of nootropics influences the development of the retrograde amnesia to different extents, the treatment regimen (application of the drug only during the training and supplementary pretreatment before the first day of training; respectively) being of importance. The antiamnestic effect of Piracetam (100 mg/kg, intraperitoneally) which is good also without pretreatment, may still be potentiated, especially on the fourth day of treatment, by an additional administration of the drug, beginning four days before the first day of treatment. In contrast to this, meclofenoxate hydrochloride (100 mg/kg, intraperitoneally) and pyritinol (100 mg/kg, intraperitoneally) produce a marked inhibition of the development of the retrograde amnesia only after pretreatment. Without pretreatment these drugs exert a slight or no effect. The marked antiamnestic effect of methylglucaminorotate (225 mg/kg, intraperitoneally) and by an additional pretreatment. As to dihydroergotoxin (1 mg/kg; intraperitoneally), both treatment regimens were ineffective in the model used.
The substance P when administered intracerebroventricularly (15 nmol) led to a transformation of feeding elicited by threshold electrical stimulation of the lateral hypothalamus into an escape reaction in rabbits. Obsidan, Inderal (0.25 and 0.5 mg) and droperidol (0.3 mg) injected intravenously were found to restore the functional properties of the hypothalamic feeding centre. No changes in the escape reaction were observed after kalipsol (ketaminum) administration. The data obtained suggest the important role of the catecholaminergic brain structures in the mechanisms of the transformation of the functional properties of the hypothalamic feeding centre under the influence of the substance P.
An ability of substance P (15 nmol intracerebroventricularly) to transform functional properties of the hypothalamic feeding center manifested in escape reaction in response to threshold electrical stimulation of this motivation center in rabbits. Beta-adrenergic antagonists inderal and obsidan (0.25, 0.5 mg, respectively) injected intravenously were found to restore feeding elicited by electrostimulation of the hypothalamic feeding center. However, escape reaction, elicited from the feeding center under substance P was found unchanged after intravenous administration of 0.25 mg kalipsol. The data obtained suggested an important role of beta-adrenergic mechanisms in substance P transformation of the functional properties of the hypothalamic feeding centre.