Biomedical subjects

Heather S Oliff

Publications and source records attributed to Heather S Oliff.

3 recordsLinked to original sources

PubMed2004

Age-dependent effects of nicotine on locomotor activity and conditioned place preference in rats.

RATIONALE: Most adult smokers start smoking during their adolescence. This adolescent initiation may be due to multiple factors, but little evidence is available regarding whether their brains are differentially sensitive to the addictive effects of nicotine during adolescence. OBJECTIVE: To test the hypothesis that adolescents are more sensitive than adults to nicotine's rewarding actions. METHODS: An unbiased, counterbalanced, place-conditioning procedure was used to examine drug-induced reward and locomotor activity. Early adolescent (postnatal day 28), late adolescent (P38) and adult (P90) rats received either saline or nicotine (0.125, 0.25 or 0.5 mg/kg, s.c.) and were tested for place conditioning. RESULTS: During early adolescence, a single nicotine injection (0.5 mg/kg) induced significant conditioned place preference (CPP). In contrast, during late adolescence or adulthood, nicotine did not induce CPP after either one or four conditioning trials. Initial locomotor responses to acute nicotine administration during the first conditioning trial also differed with age, with no effect at P28, but substantial inhibitory responses at all doses studied (0.125-0.5 mg/kg) at later ages. Although not differing in their initial locomotor response to nicotine, there was a significantly greater tolerance/sensitization during the second and subsequent drug exposures in late adolescents than in adults. CONCLUSIONS: These findings provide evidence that adolescent brain is differentially sensitive to both the acute and repeated effects of nicotine relative to adult brain. Furthermore, there are significant differences in nicotine sensitivity between early and late phases of adolescence.

Aging↗

PubMed2003

Cerebral spinal fluid pressure: effects of body position and lumbar subarachnoid drainage in a canine model.

STUDY DESIGN: This study used in vivo an model of subarachnoid cerebrospinal fluid pressure measurement. OBJECTIVES: To examine the relation between subarachnoid cerebrospinal fluid pressure in the cervical and lumbar spine and varying body positions, and to test the hypothesis that increasing body inclination and lumbar subarachnoid drainage decreases cervical cerebrospinal fluid pressures. SUMMARY OF BACKGROUND DATA: Cerebrospinal fluid leaks are a recognized complication of anterior or posterior cervical surgery. Conflicting opinion exists regarding the benefits of postoperative patient positioning and lumbar subarachnoid drainage. METHODS: Subarachnoid cerebrospinal fluid pressure of 7 beagles was monitored via two angiocatheters attached to pressure transducers inserted into the subarachnoid space through laminectomies at C3 and L4. Pressure measurements were taken when body position was inclined to 30 degrees, 60 degrees, and 90 degrees. A lumbar durotomy was performed to simulate the effects of lumbar subarachnoid drainage. The body was repositioned to 90 degrees, and pressure was measured. RESULTS: As inclination increased from 0 degrees to 90 degrees, the mean cervical cerebrospinal fluid pressure significantly decreased. The mean lumbar subarachnoid pressure significantly increased as inclination increased from 0 degrees to 90 degrees. Lumbar durotomy plus repositioning to 90 degrees resulted in a significant reduction in cervical cerebrospinal fluid subarachnoid pressure, with pressures dropping by 46%. Lumbar cerebrospinal fluid subarachnoid pressure dropped to zero after lumbar durotomy plus repositioning to 90 degrees. CONCLUSIONS: Cerebrospinal fluid pressures in the subarachnoid space of both the cervical and lumbar spines are affected by changes in body position. Both patient positioning and lumbar drainage may be important in reducing cervical cerebrospinal fluid pressure, and may reduce the occurrence of cerebrospinal fluid leaks after primary dural repair in the neck.

Animals↗

PubMed2003

Sustained spinal cord compression: part I: time-dependent effect on long-term pathophysiology.

BACKGROUND: The objective of this study is to determine whether there is a relationship between the duration of sustained spinal cord compression and the extent of spinal cord injury and the capacity for functional recovery after decompression. METHODS: Sixteen dogs underwent sustained spinal cord compression for thirty or 180 minutes. The cords were compressed with use of a loading device with a hydraulic piston. A pressure transducer was attached to the surface of the piston, which transmitted real-time spinal cord interface pressures to a data-acquisition system. Somatosensory evoked potentials were monitored during a sixty-minute recovery period as well as at twenty-eight days after the injury. Functional motor recovery was judged throughout a twenty-six-day period after the injury with use of a battery of motor tasks. The volume of the lesion and damage to the tissue were assessed with both magnetic resonance imaging and histological analysis. RESULTS: Sustained spinal cord compression was associated with a gradual decline in interface pressure. Despite this, there was continuous decline in the amplitude of the somatosensory evoked potentials, which did not return until the cord was decompressed. Within one hour after the decompression, the dogs in the thirty-minute-compression group had recovery of somatosensory evoked potentials, but no animal had such recovery in the 180-minute group. Recovery of the somatosensory evoked potentials in the thirty-minute group was sustained over the twenty-eight days after the injury. Motor tests demonstrated rapid recovery of hindlimb motor function in the thirty-minute group, but there was considerable impairment in the 180-minute group. Within two weeks after the injury, balance, cadence, stair-climbing, and the ability to walk up an inclined plane were significantly better in the thirty-minute group than in the 180-minute group. The longer duration of compression produced lesions of significantly greater volume, which corresponded to the long-term functional outcome. CONCLUSIONS: The relatively rapid viscoelastic relaxation of the spinal cord during the early phase of sustained cord compression suggests that there are mechanisms of secondary injury that are linked to tissue displacement. Longer periods of displacement allow propagation of the secondary injury process, resulting in a lack of recovery of somatosensory evoked potentials, limited functional recovery, and more extensive tissue damage.

Animals↗