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Biomedical subjects

N Dafny

Publications and source records attributed to N Dafny.

At least 145 records · Page 8Linked to original sources
PubMed1982

Electrophysiological support in favor of multiple opiate receptors in the caudate and the central gray of the rat.

1. The present study compares the direct actions of morphine on two brain sites known to be rich in opiate receptors, namely, the caudate nucleus and the central gray. Recordings and morphine injections were made through a multibarrel glass micropipette using microiontophoresis. 2. Four different patterns of neuronal response to increasing currents of morphine were recorded in both brain regions. 3. Differences in the response to morphine between the two sites were detected in morphine-dependent rats. While the caudate neurons exhibited super-sensitivity to morphine, the neurons in the central gray displayed tolerance, and in some instances, dependence was evident when naloxone was administered. 4. The distribution of spontaneously active neurons within these two brain areas was found to be different in morphine-naive and morphine-dependent rats. 5. The electrophysiological findings of this study support the hypothesis of multiple opiate receptors.

Animals↗
PubMed1982

Caudate neuronal response to microiontophoretically injected morphine in naive and morphine-dependent rats.

1. The response of caudate nucleus neurons to morphine was found to be dose-dependent and could be divided into two classes: neurons which responded monophasically either by increase or decrease in their firing rate, and neurons whose response can be described as biphasic, exhibiting increase followed by decrease in their firing rate or vice versa, with the increase in morphine concentration. These responses were found in both naive and morphine-dependent rats. 2. Naloxone antagonized the effects of morphine in 74 out of 102 neurons tested. 3. Caudate neurons of morphine-dependent rats showed super-sensitivity to morphine compared to naive rats. 4. Differences were found in the distribution of the spontaneously active neurons between naive and morphine-dependent rats, indicating the existence of two different opiate receptor populations within the caudate nucleus.

Animals↗
PubMed1982

Dorsal raphe nucleus modulates sensory evoked responses in caudate and septum.

The dorsal raphe nucleus (DR) was examined for its possible modulatory effects on sensory input to the caudate nucleus (CN) and lateral septum (Spt) in freely behaving rats. Three types of DR stimulation were tested for their effects on sensory evoked responses: (1) a single pulse of electrical stimulation of the DR prior to each sensory stimulus, (2) a 5-20 min burst of 20 Hz stimulation of the DR prior to sensory stimulation, and (3) a combination of the single pulse and the 5-20 min burst (20 Hz) stimulation of the DR prior to the sensory stimulation. Each of the three forms of DR stimulation caused a decrease in the amplitudes of the sensory-evoked responses recorded from the CN and Spt. Combination of DR stimulation caused stronger (summation) attenuation of the sensory responses. Thus, DR was shown to affect sensory input recorded in CN and Spt.

Animals↗
PubMed1981

Periaqueductal gray neurons response to microiontophoretically injected morphine in naive and morphine-dependent rats.

The attempt of this study was to investigate the direct effects of increasing doses of morphine on the neuronal activity of the periaqueductal gray in morphine-naive and morphine-dependent rats. The microiontophoresis technique was used for this purpose. The four different responses induced by morphine exhibited dose-related patterns. Naloxone antagonized these responses in about 40% of the cases. Differences were found in the sensitivity of the neurons of morphine between naive and morphine-dependent rats. The phenomena of acute tolerance, chronic tolerance and dependence have been found. The results of this study indicate the presence of different neural populations in the periaqueductal gray in relation to their response to morphine, supporting the notion that subpopulations of opiate receptors exist within this brain area.

Animals↗
PubMed1981

Altered caudate nucleus field potentials following sustained stimulation to different substantia nigra regions.

Evoked potential recording techniques were used as a physiological tool for electrode placement into the substantia nigra pars compacta (SNpc). It was found that when the recording electrodes were implanted at the level of the caudate nucleus (CN), typical patterns were obtained only when the stimulation electrode was located in the SNpc. When the stimulation electrode was fixed in the SNpc and four electrodes were simultaneously used to record depth profile from the caudate nucleus and the septum, the typical responses following stimulation were obtained only when electrodes were within the CN head. High frequency stimulation of the SNpc, which is known to alter dopamine content within the CN, caused a reversible diminution of responses in CN for 5-10 min. This observation was discussed in terms of terminal transmitter depletion.

Animals↗
PubMed1981

Chronic halothane modification of eeg-like activity recorded from somatosensory cortex and deep nuclei in freely behaving rats.

Chronic exposure to the anesthetic agent halothane has been implicated in morphological and biochemical alterations of central nervous system tissue. In the present experiments, analysis of electroencephalographic (EEG) recordings has been used to examine effects on brain electrical activity. EEGs were recorded from freely behaving rats with stereotaxically implanted permanent semimicroelectrodes. Recordings were taken from the somatosensory cortex (SC), nucleus parafasciculus thalami (PF), mesencephalic central gray (CG), and the ventromedial hypothalamus (VMH) before (control) and after 28 and 56 days of chronic intermittent halothane administration (0.5%, 3 hr/day, 5 days/week). On each recording day (0, 28 and 56), EEGs were obtained prior to halothane exposure and following exposure to 0.25%, 0.5% and 1.5% halothane. In halothane-naive rats (day 0), the EEG dominant frequency (DF) showed a dose-response pattern consisting of an initial increase with 0.25% (significant only for the PF) followed by suppression at 0.5% and a marked significant decrease in all regions at 1.5%. On day 28, the pre-drug DF recorded from three of four regions showed a slowing trend. Additionally, with 1.5% halothane, only the SC DF was significantly decreased. Following 56 days of intermittent exposure, the pre-drug EEG frequencies were significantly decreased in all regions as compared to naive values. Subsequent administration of 0.25% halothane produced a significant increase in all regional DFs which was also obtained with 0.5% and with 1.5% for the CG and VMH. The high DF values from the PF, CG and VMH at 0.5% and from the CG and VMH at 1.5% represent statistically significant increases over naive 1.5% values. Chronic halothane exposure is thus shown to progressively alter EEG activity and the EEG pattern of dose-responsiveness in four brain regions.

Anesthetics, Inhalation↗
PubMed1980

Visual input to rat pineal.

Electrophysiological recordings from freely behaving rats, previously implanted stereotaxically with permanent electrodes in the pineal, ventromedial hypothalamus, caudate nucleus, lateral geniculate body and medial geniculate body were obtained. The pineal photic responses revealed 5 sequential components. Injection of a neuronal blocker at the level of the superior cervical ganglion did not alter the earlier photic responses, but did eliminate the late components (N2-P3) for 60-90 min after the injection. All of the other responses were unchanged during the experiment. The present experiments demonstrated that photic input travels to the pineal through two pathways.

Animals↗
PubMed1980

The parafascicular nucleus of thalamus exhibits convergence input from the dorsal raphe and the spinal tract of the trigeminal nerve.

Single unit activity was recorded in 92 units in the parafascicular nucleus (PFN) of the rat. Stimulation electrodes were placed in the dorsal raphe (DR) and spinal tract of the trigeminal nerve (SpV). Stimulation of either the DR or SpV evoked significant changes in firing rates of PFN units. Some units responded with short latency driven activity. Driven and non-driven convergence of input was detected. These findings support the concept that the PFN may be a site of modulation of analgesia and pain appreciation.

Afferent Pathways↗
PubMed1980

Characterization of unit activity recorded from septum, thalamus, and caudate following incremental opiate treatment.

The effects of a wide range of morphine doses and of its antagonist, naloxone, on spontaneous multiunit discharges in freely moving rats were recorded simultaneously from the septum (Spt), medial thalamus (CM-PF complex), and caudate nucleus (CN). A high percentage of neurons in these three areas are affected by morphine. Neurons in the CM-PF complex exhibited a greater number of morphine-induced changes (104/145) than did those in the caudate nucleus (79/160), or in the septum (67/150). The morphine-induced changes exhibited dose-related patterns: the three structures examined in the present study exhibited four response patterns to incremental doses of morphine: either a monophasic effect, an increase or decrease in firing rate, or a biphasic effect; ie, lower morphine doses induced a decrease in activity, whereas higher doses induced an increase in firing rate. There was no observed correlation between the response patterns in the three regions. The technique provides a tool with which to identify and classify the specific response patterns induced by morphine in specific brain regions, and the results may indicate that each region plays a different physiological role in the effects induced by morphine.

Animals↗
PubMed1980

Neurophysiological evidence for tolerance and dependence on opiates: simultaneous multiunit recordings from septum, thalamus, and caudate nucleus.

Multiunit activity was recorded simultaneously from the septum (Spt), medial thalamus (PF-CM complex), and caudate nucleus (CN) in freely behaving rats previously implanted with permanent nichrone semimicroelectrodes (62 mu in diameter). A challenge dose of morphine (10 mg/kg) and its antagonist (naloxone 1.0 mg/kg) was examined in the same animals while they were morphine naive and after they had become morphine physically dependent. Electrophysiological observations indicated that it would be possible to identify three physiological phenomena: 1) activity related to morphine dependency; 2) activity related to tolerance; and 3) activity related to withdrawal. Experimental observations yielded three different electrophysiological patterns of activity related to tolerance. Each of the three central sites (Spt, PF-CM, and CN) exhibited a different response pattern to morphine in morphine physically dependent animals.

Animals↗
PubMed1980

Effects of morphine on sensory-evoked responses recorded from central gray, reticular formation, thalamus, hypothalamus, limbic system, basal ganglia, dorsal raphe, locus ceruleus, and pineal body.

Field potential recordings of acoustic and photic-evoked responses were obtained from 15 brain sites of freely behaving unanesthetized rats previously implanted stereotaxically with permanent electrodes. Several dosages of morphine (1, 5, 10, 30, and 50 mg/kg) were examined. The activities recorded from all the structures in this study, except the cochlear nucleus (CoN), were affected by morphine. Different sensitivities to morphine threshold were observed between structures, and several structures exhibited dose-related patterns (ventromedial hypothalamus (VMH), caudate nuucleus (CN), central gray (CG), hippocampus (Hipp), and lateral septum (Spt)). Several brain sites, after the initial dose of morphine, did not recruit more responses to subsequent doses of the drug, ie, exhibited all-or-none responses (pineal body (PB), medial thalamus (MTh), anterior hypothalamus (AH), mesencephalic reticular formation (MRF), and the dorsal raphe (DR)). In some structures, morphine induced increases in the response amplitudes, while in other sites decreases in response amplitudes were elicited. Biphasic responses, ie, increases in response amplitude after low doses of the drug and decreases in response amplitude after higher dosages, were also observed (VMH, CN, DR, CG, and MRF). The acoustic-evoked responses were affected by morphine more than the photic responses. The present observations indicated that 1) morphine exerts effects in many parts of the central nervous system (CNS); 2) some structures are more sensitive to morphine than others; 3) only a few structures exhibit dose-related patterns and, thus, may represent sites of direct morphine action; 4) some structures exhibit all-or-none responses; and 5) morphine depressed activity in some structures and increased activity in others, ie, morphine elicited different effects in different structures.

Acoustic Stimulation↗
PubMed1980

Photic input to rat pineal gland conveyed by both sympathetic and central afferents.

Average photic evoked responses were recorded from the pineal in light and dark adaptation. Permanent semimicroelectrodes were implanted several days before the experiments were begun. Local anesthesia (xylocaine) at the superior cervical ganglion (scg) level was used as a tool to determine whether or not photic responses are transmitted via the scg and/or through another CNS route. The experiments demonstrated that in dark adaptation, photic evoked responses recorded from the pineal exhibited higher amplitude. Moreover, the photic evoked responses are transmitted via two separate routes: one, a faster pathway with a "shorter" latency, via the CNS, i.e. the habenular posterior commissure complex, and the other a "slower" (or longer) pathway via the reticular formation scg to the pineal.

Afferent Pathways↗