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Biomedical subjects

M Segal

Publications and source records attributed to M Segal.

At least 379 records · Page 21Linked to original sources
PubMed1971

Control of responding by location of auditory stimuli: rapid acquisition in monkey and rat.

Monkeys require a considerably larger number of trials to bring responding under the control of the location of an auditory stimulus than cats, rats, and bats with the same experimental procedures. The present experiment sought to determine the conditions necessary for rapid acquisition of control of responding by location of noise and tone bursts in the monkey. Monkeys were run in an enclosure that contained four loudspeakers and four manipulanda. Two conditions were used in training. In the adjacent condition, a stimulus (noise or tone burst) was presented through one or other of two speakers and a response on the manipulandum adjacent to the speaker was reinforced with food. In the nonadjacent condition, a stimulus was presented through one of two speakers and a response on a manipulandum remote from the speaker was reinforced with food. Acquisition of control was measured by change in the percentage of reinforced responses during training. In the adjacent condition, responding came under control of location within zero to three sessions. In nonadjacent conditions, the animals required 14 to 20 sessions to come under control of location. These latter numbers are comparable to those reported in the literature for localization discrimination in monkeys.

Animals↗
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Quantitative histochemistry of brain acetylcholinesterase and learning rate in the aged rat.

Using a newly developed method for quantitative acetylcholinesterase (AChE) histochemistry we find a substantial decrease in AChE content in aged rats compared to young controls in the cholinergic cell body regions (the ventral pallidum and the medial septal nuclei) and, to a smaller extent in the projection areas (the cortex and hippocampus). In the same group of aged rats we find a severe deficit in the acquisition of a water maze task. Quantitative histochemistry is a potent method for detecting localized changes in AChE content in otherwise intact, learning-impaired aged rats.

Acetylcholinesterase↗
PubMedDate not supplied

Aging and brain cholinergic muscarinic receptor subtypes: an autoradiographic study in the rat.

Cholinergic M1 and M2 muscarinic receptors in aged and young rat brains were studied by quantitative autoradiography of tritiated QNB in the presence of pirenzepine or carbachol. A selective pattern of decreased binding density was observed in the aged rat. A large number of regions showed no effect of aging; these include subdivisions of the hippocampal formation and most thalamic and hypothalamic nuclei. M1 and M2 receptors showed small but significant decreases in cortical regions and in the striatum. The largest effects were seen in M2 receptors of the ventral forebrain cholinergic nuclei where binding was reduced by up to 40%. No similar reductions were seen in the M1 receptor population in these regions. The results suggest that both muscarinic receptor subtypes show an anatomically selective pattern of decrease with age, with the M2 receptor subtype in the basal forebrain nuclei being specially vulnerable to the effects of aging.

Aging↗
PubMedDate not supplied

Regional changes in NGF receptor immunohistochemical labeling in the septum of the aged rat.

A monoclonal antibody to the nerve growth factor receptor (NGFR) (IgG 192) was used to visualize differences in immunohistochemical labeling of young (10 months) and old (35 months) rats. Three parameters were analyzed; cell counts, immunoreactive cross-sectional surface area (SA) and optical density (OD) of labeled cells. Large reductions in all three parameters were recorded in the medial septum (MS). Both OD and immunoreactive SA were reduced in the VDB, while only OD was reduced in the HDB. This observation confirms that NGFR labeling is reduced in the aged rat septum and adds that the loss of labeling is differential, with greater deficits in the MS-VDB complex than in the HDB.

Age Factors↗
PubMedDate not supplied

Effect of 5-hydroxytryptophane on behavior and hippocampal physiology in young and old rats.

Spatial memory ability, tested in a water maze, was severely impaired in control, 24-month-old hooded rats. A daily injection of the serotonin precursor, 5-hydroxytryptophane (5-HTP), prior to training sessions, had no effect on the behavior of the young rats but improved considerably the performance of the old rats in the watermaze. In the same groups of young and aged rats, the response properties of the hippocampal dentate gyrus to perforant path stimulation was assessed before and after parenteral administration of 5-HTP. The dentate gyrus of aged rats produces a smaller EPSPs in response to perforant path stimulation but a larger population spike for a given EPSP than that produced in young rat brains. These differences are not affected by 5-HTP. In young brains, priming commissural stimulation suppresses subsequent reactivity to perforant path stimulation. This priming effect is nearly absent in aged rat hippocampus but reappears when the rat is injected with 5-HTP. It is suggested that the serotonergic innervation of the rat hippocampus plays a major role in regulation of the excitability of the hippocampus and in behavioral functions associated with this structure.

5-Hydroxytryptophan↗
PubMedDate not supplied

Neuron activity in rat hippocampus and motor cortex during discrimination reversal.

Chronic unit activity and gross movement were recorded from rats during two discrimination reversals in a classical appetitive conditioning situation. The anticipatory movement decreased in response to the former CS+ tone and increased to the previous CS- tone after each reversal. Hippocampus and motor cortex were differently related to these two kinds of behavioral change. Response rates of hippocampal neurons were more closely related to the increased movement response to the former CS- which now signaled food. Motor cortex neuron responses were more closely correlated with the decrease in movement responses to the former CS+ which became neutral after the reversal. It appeared that hippocampal neurons could have been involved in one cognitive aspect of the situation, motor cortex neurons in another. The data were related to current functional concepts of these brain regions.

Animals↗
PubMedDate not supplied

Effects of priming stimulation of catecholamine containing nuclei in rat brain on runway performance.

Rats were implanted with bipolar fine wire stimulating electrodes in the region of the pontine nucleus locus coerulus (LC) and the pars compacta of the substantia nigra (SN). The reinforcing properties of stimulation of each electrode were determined. Subsequently, rats were run in a two alley runway and the effects of priming stimulation on performance in acquisition, discrimination and reversals were measured. It was found that LC priming caused an increased latency to exit from start box. Also, LC priming reduced running time in the rewarded alley in a reversal task whereas SN priming affected both performance in the rewarded and non-rewarded alley.

Animals↗
PubMedDate not supplied

Lifetime psychiatric comorbidity rate in Israeli non-help-seeking patients with combat-related post-traumatic stress disorder.

BACKGROUND: Most of the data on lifetime psychiatric comorbidity in combat-related posttraumatic stress disorder (CR-PTSD) were collected in help-seeking patients. METHODS: In the present study we used the Schedule for Affective Disorder and Schizophrenia-Lifetime Version to examine a relatively large sample (n=80) of Israeli non-help-seeking CR-PTSD patients. The diagnosis of PTSD was based on the DSM-III-R criteria. RESULTS: We found a low rate of lifetime psychiatric comorbidity, especially drug dependence (2.25%), alcoholism (2.25%) and major depressive disorders (5%). CONCLUSION: It seems that in contrast to help-seeking CR-PTSD, non-help-seeking CR-PTSD is associated with a low frequency of comorbid psychiatric disorders. LIMITATION: Only non-help seeking CR-PTSD patients who agreed to participate in the study were included in this investigation. CLINICAL RELEVANCE: The detection and diagnosis of CR-PTSD comorbidity is important for establishing appropriate psychotherapeutic and pharmacological treatment.

Adult↗
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Aging affects transcranial magnetic modulation of hippocampal evoked potentials.

Transcranial magnetic stimulation (TMS) is being proposed as a method of choice for the treatment of clinical depression, yet its action in the brain is still not well understood. In previous studies we found that TMS has a long-term effect on reactivity of the hippocampus to perforant path stimulation. Since the efficacy of antidepressants is highly age-dependent, we studied possible age-related effects of TMS on hippocampal evoked responses. Young adult (3 months), aging (10 months) and aged (24-26 months) awake rats were subjected to daily TMS for one week, followed by measurements of several parameters of reactivity to perforant path stimulation in the anesthetized rat. TMS did not affect responses of the hippocampus to single perforant path stimulation, but reduced drastically paired-pulse and frequency dependent depression in the young and aging but not the old rats. Likewise, TMS increased LTP expression in the young but not the old rats, and reduced the efficacy of serotonin modulation of reactivity of the hippocampus, in the young but not the old rats. Thus, long term effects of chronic TMS on local GABAergic inhibition are highly age dependent.

Aging↗
PubMedDate not supplied

Age-dependent local modulation of hippocampal-evoked responses to perforant path stimulation.

Local modulation of hippocampal-evoked responses to perforant path stimulation was studied by leaking drugs from the recording pipette placed in the dentate gyrus of anesthetized young (3 months old), aging (17 months old) and old (28 months old) rats. In old rats, the excitatory postsynaptic potential (EPSP) slope was much reduced compared to young and aging rats. The population spike (PS) size was similar in all age groups. Bicuculline caused a marked increase in PS size relative to population EPSP, and reversed the response to the second pulse in a paired-pulse paradigm from inhibition to facilitation. The effect of bicuculline was only slightly reduced in old rats. The 5-HT1a agonist 8-OH-DPAT potentiated PSs in the dentate gyrus, while not affecting paired-pulse inhibition. The effect of 8-OH-DPAT was slightly reduced in old rats. Carbachol, a cholinergic agonist, reversed paired-pulse inhibition into facilitation in the young brain, but not in aging and old rats. These results demonstrate that age affects differentially the action of biogenic amines on hippocampal reactivity to afferent stimulation.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMedDate not supplied

A Ca-dependent Cl- conductance in cultured mouse spinal neurones.

Long-lasting conductance changes triggered either by brief (millisecond) electrical stimuli and/or entry of calcium ions have been observed in a variety of excitable tissues. The electrical consequences of these events depend on the ion conductance affected and on the ion concentration gradient across the membrane, while the long-lasting nature of the change sustains the cell at either sub- or supra-threshold levels for activation of regenerative action potentials. We report here that many cultured mouse spinal neurones exhibit a voltage-activated chloride conductance that lasts for seconds and is dependent on extracellular calcium, [Ca2+]0. This conductance may repolarize and stabilize the cell at a level subthreshold for generating action potentials, thus complementing the functional roles of Ca-dependent K+ conductances.

Animals↗