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Biomedical subjects

A Lavin

Publications and source records attributed to A Lavin.

At least 19 recordsLinked to original sources
PubMed2002

Repeated cocaine administration alters the electrophysiological properties of prefrontal cortical neurons.

Recently it has become clear that some of the symptoms of addiction such as relapse to drug-taking behavior arise, in part, from a dysfunction in cognitive and emotional processing. This realization has promoted investigations into the physiology and pathophysiology of forebrain circuits that are both innervated by dopamine and play an important role in cognitive processing, including the prefrontal cortex. In order to study long-term neuroadaptations occurring in the prefrontal cortex of the rat as a consequence of psychostimulant administration, cocaine was repeatedly administered in either a contingent or a non-contingent manner. At least 2 weeks following the last cocaine injection, in vivo intracellular recordings were made from neurons located in the deep layers of the prefrontal cortex. Repeated cocaine administration abolished the presence of membrane bistability normally present in neurons located in the limbic prefrontal cortex. These results indicate that repeated exposure to cocaine produces enduring changes in the basal activity of neurons in the prefrontal cortex that may contribute to previously identify cognitive and emotional dysfunctions in cocaine addicts.

Action Potentials↗
PubMed2001

Regulation of limbic information outflow by the subthalamic nucleus: excitatory amino acid projections to the ventral pallidum.

The subthalamic nucleus (STN), a component of the basal ganglia motor system, sends an excitatory amino acid (EAA)-containing projection to the ventral pallidum (VP), a major limbic system output region. The VP contains both NMDA and AMPA subtypes of EAA receptors. To characterize the physiology of the subthalamic pathway to the VP, and to determine the influence of EAA receptor subtypes, in vivo intracellular recordings, and in vivo extracellular recordings combined with microiontophoresis, were made from VP neurons in anesthetized rats. Of the intracellularly recorded neurons, 86% responded to STN stimulation, and these displayed EPSPs with an onset of 8.7 msec, consistent with a monosynaptic input. The EPSPs evoked in spontaneously firing neurons were nearly twice the amplitude of those in nonfiring cells (13.1 vs 6.8 mV, respectively). As neurons were depolarized by current injection, the latency for spiking decreased from 24.2 to 14.2 msec, although EPSP latency was unaffected. Eighty-seven percent of the extracellularly recorded VP neurons responded to STN stimulation with a rapid and robust enhancement of spiking; the response onset, like the EPSP onset, equaled 8.7 msec. Firing rate was enhanced by NMDA in 94% of the STN-excited cells, and AMPA increased firing in 94% as well. The NMDA-selective antagonist AP-5 attenuated 67% of the STN-evoked excitatory responses, and the AMPA-selective antagonist CNQX attenuated 52%. Both antagonists attenuated 33% of responses, and 78% were attenuated by at least one. This evidence suggests that a great majority of VP neurons are directly influenced by STN activation and that both NMDA and non-NMDA receptors are involved. Moreover, the VP response to STN stimulation appears to be strongly dependent on the depolarization state of the neuron.

Action Potentials↗
PubMed2001

Stimulation of D1-type dopamine receptors enhances excitability in prefrontal cortical pyramidal neurons in a state-dependent manner.

Prefrontal cortex neurons recorded in vivo exhibit bistable activity states, consisting of a depolarized phase (-55mV) and a hyperpolarized phase (-85mV). These "up" and "down" states have durations ranging from 800ms to 1s and a periodicity of approximately 1Hz. This study examines the state-dependency of prefrontal cortical neuron responses to dopamine, in which the bistable-state was approximated in vitro by intracellular current injection. At resting membrane potential (n=10), dopamine caused a significant depolarization of the membrane potential without altering any of the other electrophysiological characteristics tested. In contrast, both dopamine (30 microM, 5min) and the D1 receptor agonist SKF 38393 (5 and 10 microM) increased cell excitability when the cell was in the depolarized state (i.e., -55mV) but not the hyperpolarized state (i.e., -85 mV; n=10). This increase in excitability was accompanied by a decrease in the rheobase current. The SKF 38393-enhanced excitability was dose-dependent and could be blocked by bath administration of the D1 receptor antagonist SCH 23390 (5 and 10 microM). Administration of the GABA antagonist bicuculline (7 microM) plus the N-methyl-D-aspartate channel blocker CPP (10 microM) produced an additional increase in the excitability of prefrontal cortex neurons that was not dependent on the membrane potential. From these data we suggest that dopamine exerts state-dependent modulatory effects on the excitability of neurons in deep layers of the prefrontal cortex.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1999

American Academy of Pediatrics. Committee on Child Abuse and Neglect and Committee on Community Health Services. Investigation and review of unexpected infant and child deaths.

Although there is a continuing need for timely review of child deaths, no uniform system exists for investigation in the United States. Investigation of a death that is traumatic, unexpected, obscure, suspicious, or otherwise unexplained in a child younger than 18 years requires a scene investigation and an autopsy. Review of these deaths requires the participation of pediatricians and other professionals, usually as a child death review team. An appropriately constituted team should evaluate the death investigation process, review difficult cases, and compile child death statistics.

Adolescent↗
PubMed1998

Dopamine modulates the responsivity of mediodorsal thalamic cells recorded in vitro.

The mediodorsal thalamic nucleus (MD) receives convergent inputs from subcortical limbic structures that overlap with a dopaminergic (DA) innervation. In this study, we describe the effects of DA agonists on the basal and evoked electrophysiological activity of identified thalamic cells of rats recorded in vitro. Administration of the D1 agonist SFK 38393 (10 microM) did not produce a clear effect on the physiological properties of the thalamic cells recorded. In contrast, bath administration of the D2 agonist quinpirole (10 microM) resulted in an enhancement of membrane excitability, facilitation of the occurrence of low-threshold spikes (LTSs), and changes in the resting membrane potential of the thalamic cells tested. The quinpirole-mediated responses were reversed by administration of the D2 antagonist haloperidol. Results from experiments performed with different [K+] and K+ channel blockers suggest that the effects of quinpirole are mediated at least in part by changes in K+ conductances. The results from this study suggest that DA can modulate the excitability of thalamic cells and in turn may influence the way that the thalamocortical system integrates information.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1998

Response of the ventral pallidal/mediodorsal thalamic system to antipsychotic drug administration: involvement of the prefrontal cortex.

Intracellular recordings were obtained from rat ventral pallidal (VP) and mediodorsal thalamic (MD) cells in vivo and the effects of antipsychotic drugs on their basal and evoked electrophysiological characteristics were assessed. Administration of either haloperidol or clozapine caused a significant decrease in the average firing rate, accompanied by a hyperpolarization of the membrane potential in the VP cells recorded. However, neither drug induced a substantial change in the other basic membrane properties of the MD cells or VP cells tested. In addition, in 50% of the MD cells tested, both antipsychotic drugs caused a change in spike discharge from an oscillatory pattern to a tonic discharge mode. In rats that had received ibotenic acid lesions of the prefrontal cortex (PFCtx) 4-8 weeks prior to recording, cells in the VP exhibited similar changes in firing frequency in response to haloperidol administration as those in the intact rats. However, in contrast to the intact rats, MD cells recorded from rats with PFCtx lesions exhibited a significant increase in firing rate after haloperidol administration. The results from this study suggest that the prefrontal cortex plays a role in modulating the response of the thalamus to antipsychotic drugs.

Animals↗
PubMed1996

Computer reminders improve on-time immunization rates.

OBJECTIVES: This study examines the effectiveness of computer-generated telephone reminders in improving infants receiving on-time immunizations. A computer called parents at home, reminded them of their child's visit, and asked if they could keep the appointment. If parents either canceled or failed to honor the appointment, the computer called back a few days later and asked them to reschedule. METHODS: A medical assistant recruited 124 consecutive mothers to receive automated computer reminders. These mothers' infants were younger than 6 months, were being seen at an outpatient clinic for a first visit, and were patients of three attending physicians and three nurse practitioners. These infants were compared to 89 infants from the same clinic, in the same age range, who were being seen for the first time during the same period by the same providers but not contacted by the medical assistant. Subjects were selected from mothers who brought their infants for their first visit in an outpatient urban clinic that serves predominantly minority clients. A research assistant reviewed patients' medical records and collected the infants' birthday, mothers' age, race, source of payments, and the immunization record of the infants. Immunization was considered to be late if, at the time of the first visit, it was more than 30 days past due for any of the recommended immunizations of the American Academy of Pediatrics, except for Hepatitis B vaccine which was not recommended at the time of the study. The dependent variable was on-time immunization. The independent variables were age of the mother at baseline, age of the child at baseline, and membership in either the comparison or the experimental group. Chi-square tests and logistic regression were used to analyze the data. RESULTS: The participation rate for appointments for the experimental group was 82%, as compared to a 69% overall participation rate for the clinic providers. The on-time immunization rate for experimental subjects was 67.8%, whereas the comparison group had an on-time immunization rate of 43.4% (differences were significant at alpha levels less than 0.01). CONCLUSIONS: Computerized reminders sent to the parents led to an increase in participation rate at the clinic and an increase in on-time immunization for their infants.

Adult↗
PubMed1996

Physiological properties of rat ventral pallidal neurons recorded intracellularly in vivo.

1. The physiology of ventral pallidal (VP) cells was investigated using in vivo intracellular recording and staining techniques in adult rats. Based on electrophysiological criteria, three different types of cells were found: type A cells, which fired phasic spikes that did not exhibit a substantial afterhyperpolarization (AHP), type B cells, which exhibited a slow ramplike depolarization that preceded the short-duration action potential; the spike was followed by a prominent AHP, and type C cells, which were the only cells that fired spikes in couplets or bursts, with the spikes in a burst exhibiting a progressive increase in duration and a decrease in amplitude. These cells also exhibited a rebound low threshold spikelike event. Furthermore, 18% of the VP cells recorded exhibited a slow subthreshold oscillation of the membrane potential (< 1 Hz). 2. The response of VP cells to stimulation of fibers arising from the prefrontal cortex, nucleus accumbens, and mediodorsal thalamic nucleus (MD) was examined. In contrast to our initial predictions, all cells responded to nucleus accumbens stimulation with excitation. Type A and B cells responded to nucleus accumbens stimulation with excitation and to MD stimulation with antidromic-like responses, orthodromic excitation, or evoked inhibitory postsynaptic potentials. Only type A cells responded to prefrontal cortical stimulation. Type C cells only responded to stimulation of the nucleus accumbens, which resulted in evoked excitatory postsynaptic potentials. 3. The cells in the VP therefore can be segregated into three physiologically defined groups according to action potential discharge patterns and their response to afferent fiber stimulation.

Action Potentials↗
PubMed1992

A survey of pediatric management of dyslipidemias in New England.

We recently surveyed physicians attending the New England Pediatric Preventive Cardiology Society. Sixteen physicians who actively evaluated children with dyslipidemia completed questionnaires; at least one representative from six of the seven medical schools in New England was included. The survey elicited responses to five hypothetical cases of childhood dyslipidemia which were representative of the types of lipid problems commonly referred to pediatric lipid specialists. Diet modification was the initial treatment of choice of all participants. For any set of lipid values, postpubertal age increased the proportion of respondents who would have prescribed medication. When pharmacologic intervention was elected, resin binders (cholestyramine or cholestipol) and niacin were most commonly prescribed. The responses of the physicians showed considerable variation in the threshold for beginning medications. In summary, this survey suggests substantial variation in the approach to pharmacologic management of pediatric dyslipidemias in the New England region.

Adolescent↗