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R D Russell

Publications and source records attributed to R D Russell.

13 recordsLinked to original sources
PubMed1991

Activation of substantia nigra pars reticulata neurons: role in the initiation and behavioral expression of kindled seizures.

Numerous studies have implicated the substantia nigra pars reticulata (SNR) in the initiation and behavioral expression of kindled seizures. In immobilized, amygdala-kindled animals, SNR neurons have been shown to enter an intense burst-firing pattern during afterdischarge (AD). Taken together these findings raised the possibility that the SNR facilitates the expression of kindled seizures by directly propagating seizure activity into target structures. In this study we examined the relationship between activation of SNR neurons and the electrical (EEG) and behavioral (clonic motor) expression of kindled seizures using both immobilized and unrestrained animals. The principal findings were that: (1) in both immobilized and unrestrained animals the SNR neurons of kindled, but not control, animals were recruited into a burst-firing pattern during AD; (2) the onset of burst-firing was delayed until after the onset of AD; and (3) the onset of burst-firing was not correlated with the onset of rhythmic motor seizure activity. These findings support the idea that the development of kindling is associated with recruitment of SNR neurons into a seizure propagating network. However, these data suggest that activation of SNR neurons is not necessary for the expression of clonic motor activity and does not lower seizure threshold.

Amygdala↗
PubMed1989

Twenty-four-hour post-seizure inhibition during limbic kindling requires seizure generalization.

Male Long-Evans rats were kindled by stimulation of the pyriform cortex using an afterdischarge (AD) threshold procedure that triggered one AD every 24 h. AD threshold dropped rapidly as long as the seizures remained localized, reaching an asymptote of 30% of its initial value by the 6th AD. In contrast, AD threshold rose progressively across the first six generalized seizures (i.e. ADs accompanied by forelimb clonus). This elevation in threshold was dependent upon the daily elicitation of a generalized seizure, and the threshold returned to its previous low value after 4 seizure-free days. This indicates that post-seizure inhibition in the pyriform cortex is a transient response produced by generalized seizures and is not related to the relatively permanent changes that underlie kindling.

Animals↗
PubMed1989

A word of caution in acute pain management.

Within acute pain management, as within any rapidly expanding field of therapeutic endeavor, novel treatment modalities may on occasion overreach their scientific foundations. In general, a cautionary theme is expressed regarding the utilization of various therapies, lest their overzealous clinical implementation jeopardizes the advancement of this highly promising field. With regard to demand-mode opioid therapeutics in particular, several areas in need of corroborative or elucidative research have been delineated. The subject of dosing for acute pain conditions with opiates via the epidural route versus intravenous opioid administration is discussed from the perspectives of practicality and risk/benefit assignments. The advisability and means of using demand-mode techniques in order to resolve the central issue of inherent benefits of opioid administration via one route or another is also presented.

Acute Disease↗
PubMed1988

Anticonvulsant and antiepileptogenic actions of MK-801 in the kindling and electroshock models.

The actions of MK-801, a noncompetitive antagonist at the N-methyl-d-aspartate subtype of excitatory amino acid receptor, were investigated on the development of kindling and on seizures in the electroshock and kindling models. The drug MK-801 potently and effectively suppressed the tonic hindlimb extension component of electroshock-induced seizures; it also suppressed both the electrophysiological and behavioral manifestations of the development of kindling. In contrast to its effects on electroshock-induced seizures and the development of kindling, MK-801 only partly reduced the duration of seizures in fully kindled animals and did not elevate the threshold for afterdischarge despite the use of a large dose, associated with profound untoward behavioral effects. Together with previous findings, these results support the idea that noncompetitive blockade of NMDA receptors markedly inhibits the development of kindling. The diminished effectiveness of MK-801 against kindled seizures suggests that MK-801 will not be a clinically-useful anticonvulsant against complex partial seizures.

Amygdala↗
PubMed1988

Some cardiovascular effects of the insect repellent N,N-diethyl-m-toluamide (DEET).

Initial toxicological safety evaluations of the insect repellent N,N-diethyl-m-toluamide (DEET) indicated a potential hypotensive effect. The current study was initiated in order to pursue this aspect of DEET toxicity and to elucidate potential mechanisms for this response. Sublethal intraperitoneal injections of DEET in anesthetized rats were found to decrease mean blood pressure and heart rate in a dose-related fashion. Doses ranged from 56 to 225 mg/kg. Dogs treated with 225 mg/kg of DEET exhibited a similar hypotension and bradycardia. Cardiac output was also significantly reduced but stroke volume and total peripheral resistance were not altered. Lead II ECG changes included small increases in P-R and Q-T intervals. In a series of pharmacological studies in rats, DEET was found to decrease the hypotension and bradycardia associated with acetylcholine injection; epinephrine, norepinephrine, and histamine responses were not altered. Atropine pretreatment reduced but did not eliminate the hypotensive effects of DEET.

Acetylcholine↗
PubMed1988

Conservative management of Tumarkin's otolithic crisis.

Tumarkin's otolithic crisis (TOC), characterized by a sudden drop attack without accompanying loss of consciousness, vertigo or autonomic signs, is a rare phenomenon thought to be of peripheral origin and associated with late-stage Meniere's disease. The purpose of this paper is to describe the clinical course of TOC in our series; to discuss the relationship between TOC and the onset and symptomatology of pre-existent Meniere's disease, and to determine the management of patients with TOC.

Adult↗
PubMed1987

Continuous intrathecal opioid analgesia: tolerance and cross-tolerance of mu and delta spinal opioid receptors.

The tolerance effects of continuous intrathecal infusions of opioids at mu and delta receptors were studied in rats. These effects were compared to those of chronic systemic morphine. A chronic intrathecal infusion of the relatively selective delta agonist, [D-Ala2, D-Leu5]enkephalin (DADLE), produced a larger degree of tolerance to DADLE than to the highly specific mu-activating morphiceptin analog [N-methyl-Phe3, D-Pro4]morphiceptin (PL017). The slope of the analgesic dose-response curve for the highly specific delta agonist, cyclic [D-Penicillamine2, D-Penicillamine5]enkephalin (DPDPE), was significantly different (flatter) from those of mu agonists or DADLE. High-dose infusion of PL017 induced a 61-fold parallel shift of the dose-response curve for PL017. This same treatment also induced a corresponding flattened, nonparallel change of the dose-response curve for DADLE. This altered curve for DADLE was very similar in slope to that of DPDPE. Pretreatment with the irreversible mu antagonist, beta-funaltrexamine, caused a parallel rightward shift of the dose-response curve for PL017 but did not affect DPDPE activity. beta-Funaltrexamine treatment induced a nonparallel rightward shift of the dose-response curve for DADLE with a change of slope similar to that of DPDPE. These findings demonstrate a mixed mu-delta analgesic activity for the compound DADLE, which is often referred to as a prototypic delta agonist. These interactions differ from prior reports of none or minimal mu-ligand interactions with DADLE. Despite the cross-reactivity of DADLE to mu receptors, DADLE remains a more effective analgesic than do mu agonists in states of mu receptor tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesia↗
PubMed1986

Interaction between highly selective mu and delta opioids in vivo at the rat spinal cord.

Possible interactions between mu- and delta-receptors in the rat spinal cord were studied using the radiant-heat-induced tail flick response and the highly selective mu- or delta-ligands: [NMePhe3,D-Pro4] morphiceptin(PL-17) and cyclic[D-Pen2,D-Pen5]enkephalin(DPDPE). Intrathecal infusions of PL-17 (0.5 microgram/hr) for 5 days caused 61- and 6-fold shifts to the right of the dose-response curves for PL-17 and DPDPE, respectively. Since PL-17 and DPDPE are highly selective agonists for mu- and delta-receptors, the partial cross-tolerance to the delta-agonist induced by PL-17 is probably not resultant from a cross-reactivity between these ligands. These data suggest that there may be an interaction between mu- and delta-receptors in the rat spinal cord.

Analgesics↗
PubMed1979

Percutaneous embolization to control intractable epistaxis.

Recurrent epistaxis is a common manifestation of patients with a bleeding diathesis. Two patients with epistaxis secondary to a bleeding diathesis managed by local conservative techniques are reviewed. (A case of polycythemia vera and a case of liver failure secondary to hepatoma are reviewed.) Recently bilateral, percutaneous carotid angiography examination was performed on a patient with a bleeding diathesis and intractable epistaxis. At the time of the angiographic examination, embolization of both internal maxillary arteries with Gelfoam particles was accomplished and dramatic control of the epistaxis was achieved. In a patient with severe epistaxis secondary to a bleeding diathesis that is unresponsive to local measures, percutaneous Gelfoam embolization offers substantial advantages over surgical intervention.

Adult↗
PubMedDate not supplied

Educating about death.

Explore the source record for details and available documents.

Attitude to Death↗