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Biomedical subjects

N Dafny

Publications and source records attributed to N Dafny.

At least 181 records · Page 10Linked to original sources
PubMed1977

Neurophysiological assessment of site specific effects of chronic morphine administration in freely behaving rats.

Sensory evoked responses were recorded simultaneously from five structures (caudate nucleus, septum, periaqueductal gray, parafascicular nucleus and reticular formation) reported to play roles in morphine's acute actions (analgesia, dyskinesia) and in the development of tolerance. Daily recordings were made from unanesthetized male Holtzman rats before and after a challenge dose of 10 mg/kg of morphine sulfate over a four day period while tolerance was induced by multiple daily injections of morphine. Three patterns of changes were observed in the individual components of the evoked responses. 1) The challenge dose caused an initial increase in the amplitudes of the P2 and N2 components of the response in the naive rats. This effect was attenuated with each day of drug administration until day four, when the challenge dose was observed to exert no effect. This pattern occurred in the parafascicular nucleus and the septum. 2) Initial increase in P2 and N2 components by morphine was augmented for 2-3 days, after which there was a sharp drop to control values by day four. This pattern was observed in the caudate nucleus and the periaqueductal gray region. 3) Morphine caused a mixture of increases and null effects in the components over the four days. This effect was observed in the reticular formation.

Acoustic Stimulation↗
PubMed1976

Opiate and endocrine interaction: morphine effects on hypothalamus and pineal body.

Experiments were performed on male Holtzman albino rats. Stainless steel semimicroelectrodes 60 micron in diameter were implanted stereotaxically in the ventromedial hypothalamus (VMH) and in the pineal body (PB). Six to eight days following this operation, the sensory field potentials from freely behaving, unrestrained rats were averaged. After a control recording was achieved, animals were given injections i.p. with 10,30 or 50 mg/kg of morphine and recordings were resumed for 45 min. Naloxone was then administered and recordings were monitored during another 45 min period. Three consistent components of the averaged sensory evoked potentials were evaluated. In both structures following the two lower doses of morphine (10 and 30 mg/kg), increased and decreased response amplitudes were observed, while following 50 mg/kg morphine, mainly increased response amplitudes were obtained in both structures. With increased doses, the percentage of responses was increased. During the 45 min of recording after morphine, effects remained consistent. Differences in the percentage and the direction of the responses were observed between the VMH and the PB. Naloxone (1 mg/kg) reversed the morphine effect in the two structures, both the increased and decreased responses. The possible interactions between morphine and endocrine function of the two structures are discussed.

Acoustic Stimulation↗
PubMed1975

A direct input from amygdaloid complex to caudate nucleus of the rat.

Spontaneous unit activity was recorded from the caudate nucleus in rats anesthetized with urethane. Amygdaloid nucleus stimulation altered the spontaneous activity of 51 units (65% of the population tested); 23 units (29%) showed an increase and 28 (36%) a decrease of discharge rate. Moreover, 25 units (32%) responded to stimulation with stimulus-locked spikes. Post-stimulus time histograms revealed 7 patterns of response to amygdaloid stimulation. In 4 groups of cells, stimulus-locked spikes occurred followed by alteration of spontaneous discharge rate. In another 2 groups there was a change of spontaneous discharge without stimulus-locked spikes and in the final group no effect occurred. The possibility of mono-, oligo-, and polysynaptic connections from amygdaloid nuclear complex to caudate nucleus was discussed. It was suggested that an amygdalofugal connection to basal ganglia may provide a pathway whereby activity of the limbic system may exert a modulatory influence on somatic motor mechanisms.

Activation Analysis↗
PubMed1975

Integrator for qualitative and quantitative unit activity.

A simple device constructed from inexpensive components enables spike activity to be integrated and displayed in a convenient scale (spikes/sec) on a pen recorder. An input voltage threshold detection circuit is employed to eliminate any random baseline noise from being integrated. A pulse output is provided to drive a counter or accumulator so that quantitative as well as qualitative results may be obtained. A monostable multivibrator is used to insure that the integrated output is a function of the frequency of spike activity and not the amplitude or pattern of the spikes. An output isolation and buffer stage is provided to eliminate any loading effect on the filter section and also provide a gain or scaling adjustment so that the integrator may be used with practically any pen recorder.

Action Potentials↗
PubMed1975

Catecholamine-modulated field potentials in the hypothalamus.

Average evoked responses (AERs) were recorded simultaneously from 3 hypothalamic nuclei of freely behaving rats. Permanent semi-microelectrodes were implanted 6-8 days before experiments were begun. The amygdaloid AER to 32 successive stimuli consisted of large amplitude potentials made up of 3 components (P1, N1 and P2) with short latencies. The neuronal recovery function (NRF) was short. However, the acoustic AER to 32 successive acoustic stimuli in anterior hypothalamus (AH), ventromedial hypothalamus (VMH), and arcuate nucleus (AN) consisted of large amplitude potentials of long duration made up of 5 components (P1, N1, P2, and P3) with long latencies. The NRR was long. Intraperitoneal administration of L-dopa heightened the amplitude of the acoustic AER and shortened the NRF in VMH and AN. Reserpine administration 2 h after L-dopa maintained the phenomena in VMH and AN without alteration of the AER and NRF in AH. When reserpine was administered first, enhancement of the acoustic AER and shortening of the NRF was again obtained only in VMH and an L-dopa injection after reserpine treatment maintained these phenomena. Low doses of pentobarbital after L-dopa and reserpine and vice versa caused a marked increase in the acoustic AER and a shortening of the NRF in all recording sites. The amygdala AER and NRF, however, were not altered by any treatment or in any recording sites.

Amygdala↗