Light optical and electron microscopic study of the nodose ganglion neurons in emotional stress

Cell bodies of cardiovascular receptors localized in the ganglion nodosum of rabbits exposed to experimental emotional stress were studied with the light and electron microscope. Two groups of animals were selected for investigation. Under emotional stress rabbits of one group demonstrated almost unchanged arterial pressure and only a small increase in heart rate, while animals of the other group displayed strongly marked disturbances of their blood circulation leading to the lethal outcome at the end of experiment. In the first group rabbits, the microscopic anatomy and ultrastructure of the nodose ganglion neurons indicated an increased activity in the nerve cell. At the same time, morphological evidences of exhaustion were revealed in neurons of the nodose ganglion of the second group rabbits. A possible role of the distortion of the afferent information in pathogenesis of cardiovascular disorders under emotional stress is discussed.     

Monoamine oxidase activity in rabbit brain nuclei in experimental acute emotional stress

Activity of monoamine oxidase in the neurons of catecholamine-synthesizing nuclei of hypothalamic and brainstem of rabbits with different resistance of cardiovascular functions to emotional stress was studied by the Glenner et al. method. An acute experimental emotional stress was induced by non-periodic electric stimulation of the hypothalamic ventromedial nucleus and the skin in immobilized adult chinchilla rabbits. It was found that monoamine oxidase activity in the neurons of groups A5, A6, A7 and A14 under acute experimental emotional stress increased in rabbits "resistant"to stress and remained unchanged in rabbits "predisposed" to stress. The activity of monoamine oxidase in the neurons of group A12 remained unchanged in the rabbits "resistant"to stress and decreased in the rabbit "predisposed" to stress.     

Differences in activity of hippocampal and neocortical neurons in active and passive rabbits in negative emotional situations

Activities of individual hippocampal (CA1 area) and neocortical parietal-temporal neurons were compared in active and passive rabbits in negative emotional situations during emotionally significant stimuli by plotting histograms of autocorrelations. As compared to passive animals, in active rabbits, the mean firing rate of hippocampal neurons was higher, bursting and periodic oscillations of discharges occurred more frequently. Oscillation periods in the theta 1 band (6.0-9.0 Hz) appeared more frequently (in the baseline state and active exploratory or defensive reactions), whereas those in the theta 2 band (4.0-5.9 Nz), on the contrary, were infrequently observed (during freezing). The greatest changes in activity ofhippocampal neurons were observed during active locomotor responses of active rabbits. Intergroup differences in neocortical neuronal activities were less pronounced than in hippocampus. The results indicate that individual typological features in behaviour of animals appear in negative emotional situations and are reflected in activity of activity ofhippocampal (area CA1) and to lesser extent parietal-temporal neocortical neurons. The results suggest different activation levels of the septohippocampal system of active and passive rabbits and possible differences in the afferent input to the CA1 field.     

Cytophotometric study of monoamines and energy exchange enzymes in paravertebral ganglia neurons during cold and emotional stress

Concentration of monoamines and energy metabolism mechanisms was investigated in neurons of the stellate ganglion (SG) and ganglia of the thoracic sympathetic trunk Th₆-Th₁₀ (GTST) using histochemical techniques and computer analysis. Intensification of monoamine fluorescence and energy metabolism enzyme activity was found in SG neurons during both cold and emotional stress. Such changes were only observed during development of hypothermia in GTST. Selective neuronal activation is thought to take place in paravertebral ganglia under different types of stressful action.Institute of Physiology, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Neirofiziologiya, Vol. 22, No. 6, pp. 771–779, November–December, 1990.     

Structural changes in spinal ganglion neurons of lizards after cold-exposure

We studied structural changes in spinal ganglion neurons that occur in lizards exposed to the cold, both at the light and electron microscope levels. Two types of perikaryal changes were found in the cold-exposed animals: (a) In 25% of all ganglion neurons, the central region of the perikaryon was devoid of Nissl bodies and a narrow peripheral zone stained deeply basophilic. Electron microscopic examination of these cells showed that mitochondria, Golgi complexes and other organelles were assembled in the central region of the perikaryon, while most cisternae of granular endoplasmic reticulum and free polysomes were confined to the periphery of the perikaryon. These changes seem to take place mainly in dark neurons. (b) In 8.6% of all ganglion neurons, Nissl bodies were present throughout the perikaryon, but separated by large, clear spaces. Under the electron microscope, these clear spaces were filled with large numbers of densely packed filaments. It seems that mainly light neurons undergo this type of structural change. The degree of nuclear eccentricity was significantly greater in the neurons of cold-exposed animals than in controls. The nucleolar volume was significantly increased and both the percentages of nuclei with two nucleoli and of nuclei with 'vacuolated' nucleoli were significantly greater in neurons displaying structural changes than in the other neurons. The structural modifications observed in spinal ganglion neurons of cold-exposed lizards closely resemble those seen in the same lizard neurons following axonal section. They could be due to a) metabolic changes induced by low temperature and fasting, b) alterations in the flow of nerve impulses from the periphery, or c) impaired retrograde transport of trophic substances from the periphery to the cell body.     

Sensitivity of ventromedial hypothalamic neurons to thyrotropin releasing factor and bradykinin: effects of immobilization stress

In experiments on free and immobilized rabbits it was shown that ventromedial hypothalamic (VMH) neurons were characterized by specific sensitivity to TRH and bradykinin. Emotional stress in restricted animals was found to cause changes in spontaneous impulse activity of VMH neurons. Besides, the inversion of the VMH neuron sensitivity to TRH was observed while changes in the sensitivity to bradykinin were insignificant.     

Participation of angiotensin II in the establishment of negative emotional reactions

In waking rats and rabbits systemically injected angiotensin II was shown to participate predominantly in the mechanisms of negative emotional reactions. The effects of angiotensin II were observed at the behavioural level as well as at the neuronal one. Depending on the dose and the time of injection of angiotensin II and its specific antagonist saralasin they inhibited or facilitated elaboration and extinction of automatized conditioned active avoidance independently of arterial, pressure changes, the pain threshold being altered. Injection of angiotensin II abolished individual behavioural reactions of the animals in response to stress factors and increased their resistability to emotional stress. The negative emotional reactions were found to induce changes of chemosensitivity of neurones of the parafascicular complex of the medial thalamus and the midbrain reticular formation during microionophoretic application of angiotensin II. A supposition is made about the increase of angiotensin II brain synthesis under conditions of emotional stress.     

Tyrosine hydroxylase activity in rabbit autonomic nervous system ganglia in acute experimental emotional stress

The Zigmond method was made use of to study tyrosine hydroxylase activity in cervical, stellate and nodosal ganglia of rabbits predisposed and resistant to stress. Experimental acute emotional stress was induced by concurrent stimulation of the ventromedial nuclei of the hypothalamus and different skin areas. Experiments have shown that changes in metabolic activity of the sympathetic and parasympathetic systems were phasic in nature throughout 3 hours of the experiment. The changes in tyrosine hydroxylase activity in nodosal and stellate ganglia of rabbits predisposed to stress differs from those in stress-resistant animals. Stress-predisposed rabbits manifested a decrease in the activity of tyrosine hydroxylase in stellate and nodosal ganglia.     

Localization of L-glutamate decarboxylase immunoreactivity in the major pelvic ganglion and in the coeliac-superior mesenteric ganglion complex of the rat

The localization of L-glutamate decarboxylase (GAD), the GABA-synthesizing enzyme, was studied in the rat major pelvic ganglion and in the coeliac-superior mesenteric ganglion complex by indirect immunofluorescence technique with a specific antiserum raised in rabbits. GAD immunoreactivity was demonstrated in small cells of these ganglia. The GAD-immunoreactive small cells were 10-20 microns in diameter and formed clusters or occurred as solitary cells. The principal neurons were non-reactive but they were surrounded by immunoreactive processes. Studies on colocalization of GAD with tyrosine hydroxylase (TH), the rate-limiting enzyme of the catecholamine synthesis, in the major pelvic ganglion and in the coeliac-superior mesenteric ganglion complex indicated that all GAD-immunoreactive small cells were also labelled with TH. In the major pelvic ganglion all TH-immunoreactive SIF cells were also immunoreactive for GAD. However, in the coeliac-superior mesenteric ganglion complex there occurred TH-immunoreactive small cells which showed no immunoreactivity to GAD. It is suggested that the small GAD-immunoreactive cells represent small intensely fluorescent (SIF) cells.     

Interhemisphere asymmetry of hippocampus and neocortex in correlates of active and passive behavioural strategy in negative emotional situations

The interhemisphere interaction of neurons in bilateral derivations from parietal and sensomotor areas of neocortex and the area CA1 of hippocampus were studied in rabbits with active and passive behavioural strategy in the open field by plotting histograms of crosscorrelation. In passive animals, there was asymmetry in bilateral neuronal interaction: with right-sided dominance in the neocortex and with left-sided that--in the hippocampus. On the contrary, in active rabbits, the left-sided dominance was observed in the neocortex, and the lateralization was not revealed in the hippocampus. The brain laterality was reflected in motor asymmetry of animals in preferring left or right turns in the open field. Passive rabbits made relatively more left turns, and the active animals--right turns. Systemic administration of agonist GABA(B) receptors phenibut decreased behavioural responses to emotional stimuli and eliminated interhemisphere asymmetry observed usually in negative emotional situations. Thus the interhemisphere asymmetry of the neocortex and hippocampus is correlated with individual typological characteristics of animals and reflects the readiness to preferential forms of behavioural responses in active and passive rabbits.     

A study of mitochondria in spinal ganglion neurons during life: quantitative changes from youth to extremely advanced age

In view of the central role that mitochondria are thought to play in the ageing process, we investigated changes in mitochondria of spinal ganglion neurons in rabbits aged 1, 3.6, 6.7, and 8.8 years (the latter extremely old). Mitochondrial size increased significantly with age, while mitochondrial structure did not change. The total volume of mitochondria within the perikaryon did not change significantly during life. This indicates that in these neurons mitochondrial degradation was completely compensated by the production of new mitochondria even in the extremely advanced age. We also found that the mean volume of neuronal perikaryon increased markedly with age, so that the mean percentage of perikaryal volume occupied by mitochondria decreased significantly with a difference of about 33% between the youngest and the oldest animals. This decrease is only in very small part due to lipofuscin accumulation, so that the ratio of the total volume of mitochondria to the volume of functionally active cytoplasm decreased with age. The mitochondria of the neurons studied seem therefore unable to adapt their total volume to the volume of functionally active cytoplasm, that increases with age. This result is consistent with the observation that the neurons of old animals have a reduced ability to respond to high energy demands.     

Characteristics of capsaicin-sensitive afferent neurons of spinal nerve ganglia

Morphological peculiarities of neurons that had TRPV1, SP, CGRP, and NF200 markers in thoracic spinal ganglia nerves were studied in 3-month-old rats subjected to chemical deafferentation produced by capsaicin. The obtained results have shown that from 6.5 to 41.3% of ganglion neurons in the control group of animals contain, as a rule, one of the above-mentioned markers. The heterogeneity of nociceptive neurons observed in a control group of rats was also preserved in the capsaicin-treated animals. In both groups, the spinal ganglion TRPV1 neurons were predominant, whereas populations of SP, CGRP, and NF200 neurons formed smaller groups. In each population, sensitivity to capsaicin was shown in the largest neurons, regardless of marker; this sensitivity was pronounced to the greatest degree in the group of TRPV1 neurons.     

Biochemical and immunohistochemical determination of 5-hydroxytryptamine located in mast cells in the trigeminal ganglion of the rat and guinea pig

The presence of 5-hydroxytryptamine (5-HT), as well as its precursor (5-HTP) and metabolite (5-HIAA), were biochemically determinated in the trigeminal ganglion of the guinea pig and rat. The distribution of 5-HT in the ganglion and in its posterior root was studied using both indirect immunofluorescence and the peroxidase-antiperoxidase method. In order to increase the possible 5-HT content of primary sensory neurons for subsequent immunohistochemical visualization, animals were first treated with nialamide, an inhibitor of monoamine oxidase, and then loaded with L-tryptophan. Another group of animals received colchicine to inhibit intra-axonal transport of transmitter substances. However, even combined use of loading and colchicine treatment did not reveal 5-HT immunoreactivity in ganglion cells. The only source of 5-HT immunoreactivity in the trigeminal ganglion and its posterior root was mast cells. These cells were located around the ganglion in adjacent leptomeningeal and connective tissues, as well as between the ganglion cells and nerve fibers. Only occasionally were mast cells found in the posterior root of the ganglion.     

Acute emotional stress and cyclic nucleotide content of the heart and blood plasma

The relationships between the changes in arterial pressure and the content of cyclic nucleotides in the heart and blood plasma were studied on rabbits exposed to acute emotional stress. During 3 hours of the stress program, there were changes in arterial pressure, namely an elevation within the first hour followed by a progressive fall during subsequent 2 hours and death of the animals. The content of cAMP in the heart rose to a greater degree than that of cGMP. The content of cAMP in the blood plasma considerably increased, while the level of cGMP remained unchanged. The data obtained attest to the predominance of activation of adrenergic structures over activation of cholinergic structures.     

Biochemical and immunohistochemical determination of 5-hydroxytryptamine located in mast cells in the trigeminal ganglion of the rat and guinea pig

Summary The presence of 5-hydroxytryptamine (5-HT), as well as its precursor (5-HTP) and metabolite (5-HIAA), were biochemically determinated in the trigeminal ganglion of the guinea pig and rat. The distribution of 5-HT in the ganglion and in its posterior root was studied using both indirect immunofluorescence and the peroxidase-antiperoxidase method. In order to increase the possible 5-HT content of primary sensory neurons for subsequent immunohistochemical visualization, animals were first treated with nialamide, an inhibitor of monoamine oxidase, and then loaded with l-tryptophan. Another group of animals received colchicine to inhibit intra-axonal transport of transmitter substances. However, even combined use of loading and colchicine treatment did not reveal 5-HT immunoreactivity in ganglion cells.The only source of 5-HT immunoreactivity in the trigeminal ganglion and its posterior root was mast cells. These cells were located around the ganglion in adjacent leptomeningeal and connective tissues, as well as between the ganglion cells and nerve fibers. Only occasionally were mast cells found in the posterior root of the ganglion.     

Localization of l-glutamate decarboxylase immunoreactivity in the major pelvic ganglion and in the coeliac-superior mesenteric ganglion complex of the rat

Summary The localization of l-glutamate decarboxylase (GAD), the GABA-synthesizing enzyme, was studied in the rat major pelvic ganglion and in the coeliac-superior mesenteric ganglion complex by indirect immunofluorescence technique with a specific antiserum raised in rabbits. GAD immunoreactivity was demonstrated in small cells of these ganglia. The GAD-immunoreactive small cells were 10–20 m in diameter and formed clusters or occured as solitary cells. The principal neurons were non-reactive but they were surrounded by immunoreactive processes. Studies on colocalization of GAD with tyrosine hydroxylase (TH), the rate-limiting enzyme of the catecholamine synthesis, in the major pelvic ganglion and in the coeliac-superior mesenteric ganglion complex indicated that all GAD-immunoreactive small cells were also labelled with TH. In the major pelvic ganglion all TH-immunoreactive SIF cells were also immunoreactive for GAD. However, in the coeliac-superior mesenteric ganglion complex there occured TH-immunoreactive small cells which showed no immunoreactivity to GAD. It is suggested that the small GAD-immunoreactive cells represent small intensely fluorescent (SIF) cells.     

The prediction of resistance to emotional stress based on the individual testing of behavior

On the basis of the elaborated experimental model for testing of emotional interaction of animals individual typification of behaviour was established according to which all experimental male rats of August line were subdivided into groups: I--rats manifesting behaviour of avoidance, "victims" of electrocutaneous stimulation; II--without definite behaviour with respect to the "victim" rat; III--rats, preferring the behaviour determining electrocutaneous stimulation of the "victim" rat. All typified animals were subjected to emotional stress with the use of the elaborated experimental model of aggressive-conflict behaviour. Stability against emotional stress of each group of animals was studied. Significant differences were established of stability degree to emotional stress of the rats of three groups manifesting different types of behavioural reaction in conditions of emotional interaction. The most stable were rats of the I group, the least--of the III group; rats of the II group were in the middle position. Typification on the basis of testing of emotional interaction of animals allows to prognosticate individual stability against emotional stress.     

Correlation of unit activity of the right and left amygdala in food motivation and emotional stress

Correlation between activities of neurons in the right and left central nuclei of amygdala of rabbits recorded during quiet wakefulness, after 24-h food deprivation, after satiation and during emotional stress (demonstration of a dog) was studied by plotting crosscorrelation histograms. The histogram peaks shifted from zero were observed in 50-67% cases. In hungry animals, in a greater number of cases (52%), the discharge of a neuron in the left amygdala was the first in a pair, and the discharge of the right neuron was delayed (peaks from 10 to 50 and from 130 to 150 ms). The opposite order of discharges was less frequent (36%). When a rabbit saw a dog, the number of common inputs to neurons increased and the leading role of the right amygdalar neurons grew (57%) due to an increase in inhibitory influences from the right to the left amygdala. In most cases, the interaction between amygdalar neurons occurred at the frequencies of the delta range, predominantly, from 2 to 4 Hz.     

Effect of GABA receptor agonist phenibut on behavior and respiration of rabbits in the negative emotional situation

The influence of systemic injection of GABA-receptor agonist--phenibut (40 mg/kg, s/c) on open field behavior, behavioral reactivity and changes in respiratory parameters after exposure of negative emotional stimuli was studied in three rabbit groups differentiated by locomotor activity in open field (active, passive and medium-active animals). The injection of phenibut results in decrease of rabbits horizontal locomotor activity and some components of research behavior in open field and also decrease of behavioral reactivity on emotional stimuli. At the same time the probability of both an active orienting exploratory or defensive reactions and passive reactions (freezing) were decreased. The influence of phenibut depended on typological features of rabbits: the most potent effect occurred upon behavior of active rabbits, less on passive animals and practically none on medium-active rabbits. The phenibut injection results in increase of duration of inhalation during exposure to emotional stimuli, whereas it decreased in normal.     

Relation between the nature of psychotropic effects on emotional reactivity and behavior in stress situations and the status of the brain's catecholaminergic systems

Effects of psychotropic drugs on emotional reactivity and behavior under acute stress were studied in rats with 6-hydroxydopamine (6-HDA)-destroyed catecholaminergic brain terminals. The differences in emotional and behavioral reactivity were found in the group of animals who received 6-HDA. An abrupt reduction of tyrosine hydroxylase activity in corpus striatum of "emotional" rats correlates with noticeable difficulties in the behavior of escape out of stress and essential differences in the effects of psychotropic drugs whose action is mediated via the catecholamine neurotransmitter system.