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Biomedical subjects

M Segal

Publications and source records attributed to M Segal.

At least 307 records · Page 17Linked to original sources
PubMed1978

The in vivo binding of [3H]-desipramine and [3H]-chlorpromazine to areas in the rat brain.

The distribution of [3H]-desipramine (DMI) and of [3H]-chlorpromazine (CPZ) in rat brain was determined by the incorporation of radioactivity into various regions of the brain and by autoradiography of transverse cryostat sections. The label from [3H]-DMI was rapidly distributed in all brain regions, reaching peak levels within 30 min and considerably decreasing 1--4 h after injection. Following the selective destruction of catecholaminergic nerve terminals by intracerebral administration of 6-hydroxydopamine, a marked reduction in the incorporation of DMI, but not of CPZ, was evident in all brain areas investigated. The autoradiographed sections clearly demonstrated a preferential uptake of both drugs by the caudate nucleus. These findings suggest that DMI might be largely bound to presynaptic dopamine and norepinephrine terminals, while the CPZ binding involves postsynaptic sites.

Animals↗
PubMed1978

Pharmacological analysis of analgesia and self-stimulation elicited by electrical stimulation of catecholamine nuclei in the rat brain.

The relationship between intracranial self-stimulation (ICSS) and stimulation-produced analgesia (SPA) was investigated in that rat employing an operant bar-press response and a modification of the hot-plate test. ICSS and SPA were elicited through bipolar electrodes chronically implanted in two catecholamine nuclei; the nucleus locus coeruleus (LC) and the substantia nigra (SN). These sites have previously been shown to yield both phenomena. SPA was shown to be of a magnitude similar to that of morphine. In addition, SPA deriving from both LC and SN was significantly reversed by the specific opiate antagonist, naloxone. The intensity of the stimulating current sufficient to induce SPA was found to be higher than that required for ICSS. The pharmacological susceptibilities of the two phenomena were tested by administering a number of drugs: haloperidol, propranolol, pimozide and AMPT attenuated ICSS in both LC and SN, while leaving SPA unaffected. In contrast, methysergide and PCPA blocked SPA and simultaneously facilitated ICSS. The present results indicate a dissociation of ICSS and SPA from LC and SN at both physiological and neurochemical levels; ICSS rates appeared to be a function of catecholaminergic tone, while SPA depended upon the integrity of serotonin transmission.

Analgesia↗
PubMed1978

Distribution of an alpha-bungarotoxin-binding cholinergic nicotinic receptor in rat brain.

Cholinergic nicotinic receptors in rat brain were demonstrated by the use of the potent nicotinic antagonist [125I]alpha-bungarotoxin [125I]alpha-Btx). Biochemical studies on binding of [125I]alpha-Btx to rat hippocampal homogenates revealed saturable binding sites which are protected by nicotine, D-tuborcurarine and acetylcholine but not by atropine or oxotremorine. The hippocampus and hypothalamus displayed relatively high [125I]alpha-Btx specific binding whereas the cerebellum was devoid of specific binding. Other regions displayed intermediate binding levels. Analysis of the regional distribution of [125I]alpha-Btx binding by autoradiography of frontal brain sections revealed high labeling in the hippocampus, hypothalamic supraoptic, suprachiasmatic and periventricular nuclei, ventral lateral geniculate and the mesencephalic dorsal tegmental nucleus. It is suggested that the limbic forebrain and midbrain structures as well as sensory nuclei are the main nicotinic cholinoceptive structures in the brain.

Animals↗
PubMed1978

A correlation between hippocampal responses to interhemispheric stimulation, hippocampal slow rhythmic activity and behaviour.

The spontaneous electrical activity of the hippocampus as well as its responses to commissural stimulation were recorded in waking rats. Changes in magnitude of the early and late components of the response to commissural stimulation were associated with the behavioural state of the rat. The magnitude of the initial potential was higher in non-theta 'states' than in theta 'states', whereas the opposite was true for the late potential.

Afferent Pathways↗
PubMed1978

The control of responding by auditory stimuli: interactions between different dimensions of the stimuli.

Sounds have position in addition to other dimensions, such as intensity and frequency. Position rapidly gains control of spatially contiguous responses and this may interfere with control of responding by other acoustic dimensions. These experiments investigated interference of a tone-noise discrimination by the discrimination of acoustic position. Squirrel monkeys were studied when responding was differentially reinforced in the presence of both spectral content (tone-noise) and positional differences between the stimuli, and when responding was differentially reinforced only in the presence of spectral differences. Under the first condition, responding rapidly came under the control of the position of the noise in the two monkeys tested. The position of the tone controlled responding in one monkey; in the second monkey, responding came under the control of the spectral content of the tone. Under the second condition, responding was initially under the control of the noise in all three monkeys tested. This persisted for the duration of the condition for two of the monkeys; in one monkey, responding came under the control of the spectral content of the noise. Under the second condition, responding was also initially under the control of the position of the tone for all monkeys, but control by spectral content of the tone relatively rapidly developed in two of three monkeys.

Acoustic Stimulation↗
PubMed1978

Partial trisomy 18(q11 leads to qter) in an infant and aborted fetus resulting from a balanced paternal translocation t(13;18)(q32:q11).

Partial trisomy 18 is described in a two month old female with severe mental, motor and growth retardation, associated with multiple congenital anomalies characteristic of complete trisomy 18. Trisomy for almost all of 18q resulted from adjacent I segregation of a paternally inherited translocation t(13; 18)(q32:q11). The balanced translocation was observed in three generations of the family. Partial trisomy 18q identical to that observed in the proband was found in a subsequent miscarriage.

Abnormalities, Multiple↗
PubMed1977

Changes of interhemispheric hippocampal responses during conditioning in the awake rat.

The responses of the hippocampus of the awake rat to stimulation of one of its afferent pathways were measured during classical conditioning. It was found that when the contralateral hippocampus is stimulated concurrently with the presentation of a conditioned stimulus preceding either food or an aversive shock, a late (30-40 msec) negative component in the averaged evoked response can be recorded. This late component was absent when the interhemispheric stimulation was applied prior to presentation of a conditioned stimulus or when the rat was satiated or pretreated with drugs which interfere with noradrenergic or serotonergic neurotransmission. It is suggested that classical conditioning changes neurotransmission in certain pathways in the brain and that the monoamines are involved in mediation of this change.

Afferent Pathways↗
PubMed1977

The effects of brainstem priming stimulation on interhemispheric hippocampal responses in the awake rat.

Evoked hippocampal responses to stimulation of the contralateral hippocampus were recorded in the awake rat. The effects of priming stimulation applied to the nucleus locus coeruleus and the raphe nuclei on averaged evoked hippocampal responses to the interhemispheric stimulation were measured. It was found that priming stimulation of these monoamine-containing nuclei caused the formation of a late component in the interhemispheric potential without affecting the magnitude of the initial response component. Drugs which selectively interfere with noradrenergic or serotonergic transmission, antagonized the locus coeruleus or raphe primed late response component, respectively. Parenteral administration of d-amphetamine or l-amphetamine caused the appearance of a late response component which was similar to that seen after brainstem priming stimulation. It is suggested that the monoamines modify responses to afferent stimulation of particular pathways in the brain.

5-Hydroxytryptophan↗