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M M Behbehani

Publications and source records attributed to M M Behbehani.

59 records · Page 4Linked to original sources
PubMed1979

Evidence that an excitatory connection between the periaqueductal gray and nucleus raphe magnus mediates stimulation produced analgesia.

Both electrical stimulation and injection of morphine into the midbrain periaqueductal gray (PAG) produce analgesia in the rat. There is evidence that this analgesic effect is mediated by a descending system that involves nucleus raphe magnus (NRM) and adjacent reticular formation. In the studies reported here, the activity of the cells in the PAG was increased by microinjection of glutamate in this area and its effect on both the activity of single cells in the NRM and on a flexion reflex elicited by noxious heat was measured. It is shown that an increase in the firing rate of the cells in the PAG is associated with a raised threshold for flexion and is also correlated with an increase in the firing rate of a majority of the cells in the NRM. This effect on the flexion reflex can be abolished by (a) lesion of the nucleus raphe magnus and a small area of the reticular formation surrounding this nucleus and (b) by nalazone 20 min after its i.v. injection. It is concluded that there is an excitatory connection between the periaqueductal gray and the nucleus raphe magnus and that activation of this system can cause analgesia.

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PubMedDate not supplied

Preservation of retinal function in the RCS rat by laser treatment.

The Royal College of Surgeons (RCS) rats have been used as a model for human retinitis pigmentosa. Studies on these animals have shown that the degeneration of the retina is associated with a buildup of debris produced by shed rod outer segment discs. It has been reported that localized laser lesions can increase phagocytosis in these rats. This study examined the effect of laser burns on the function of the retina of the RCS rats. One eye of 19-day-old RCS rats was treated with laser and the other eye used as control. The retinal function was measured by electroretinography at 5, 10, 15, 20, 25, 30, and 40 days after lesioning. The morphology of the retina was examined at 24 and 43 days after laser treatment. The results show that the retinal function in the treated eye was improved at all intervals and that this improvement was significant at 15, 20, and 25 days. Morphologic examination showed a significant reduction in debris accumulation in the area of the laser spot. However, at sites distal to the laser burns, no morphologic difference between the treated and untreated eyes was noted. It is concluded that the progress of retinal dysfunction in the RCS rats can be retarded by laser treatment.

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PubMedDate not supplied

Enantiomer-specific effects of an intravenously administered arrhythmogenic dose of bupivacaine on neurons of the nucleus tractus solitarius and the cardiovascular system in the anesthetized rat.

BACKGROUND AND OBJECTIVE: This investigation was designed to determine whether the effects on the cell firing rate (CFR) at the nucleus tractus solitarius (NTS) and on the cardiovascular system, which are associated with a toxic dose of bupivacaine, have an enantiomer-specific component. METHODS: Adult Sprague-Dawley rats were anesthetized with chloral hydrate, and a femoral artery and vein were cannulated. After the cranial surface was exposed, a 3-mm hole was drilled 2 mm caudal and 1.5 mm lateral with respect to lambda for placement of a 1-microns tungsten microelectrode. Cells of the NTS were located 6-6.5 mm from the brain surface, and CFR was continuously recorded. Lead II electrocardiogram and arterial blood pressure were also recorded. Twenty-four animals received either d- or l-bupivacaine (2 mg/kg) in random order. RESULTS: Cell firing rates decreased from 21 +/- 13 to 0 +/- 0 impulses/second (p < 0.001) at 34 +/- 15 seconds after the injection of d-bupivacaine. Cell firing rates decreased from 22 +/- 17 to 2 +/- 4 impulses/second (p < 0.01) at 68 +/- 45 seconds after injection of l-bupivacaine. In addition to the decreases in blood pressure and heart rate that were found, all animals exhibited an inversion in electrical axis beginning within 2-3 seconds after bupivacaine administration. Mild bradycardia was noted in four of the animals receiving the l-bupivacaine, whereas severe bradycardia was observed in all animals receiving d-bupivacaine. Most important, this severe bradycardia was accompanied by progressive hypotension. In addition, all animals receiving d-bupivacaine became apneic and died, whereas all animals receiving l-bupivacaine continued to breathe and all but two of the animals survived. CONCLUSIONS: Data in the current report support the hypothesis that effects of bupivacaine on neurons of the NTS and on the cardiovascular system have an enantiomer-specific component.

Anesthesia↗
PubMedDate not supplied

Effects of an intravenously administered arrhythmogenic dose of bupivacaine at the nucleus tractus solitarius in the conscious rat.

This study was designed to further investigate the CNS-mediated cardiovascular toxicity of local anesthetics and to determine any effect of anesthesia on the firing rate of cells in the nucleus tractus solitarius (NTS) of conscious animals. Adult Sprague-Dawley rats were anesthetized with chloral hydrate. A femoral artery and vein were cannulated. A 3-mm hole was then drilled for placement of a unidirectional microdrive. The animal was removed from the stereotactic instrument, and EKG electrodes, pressure transducer and the microdrive containing a 1-micron tungsten electrode were attached. Animals were then placed in a canvas sling for recovery from the anesthetic. Cells of the NTS were located and cell firing rate (CFR) was continuously recorded. None of the animals exhibited any sign of discomfort upon recovery from anesthesia. CFRs decreased from 19 +/- 13 to 4 +/- 4 impulses/second at 20 +/- 16 seconds after the IV injection of bupivacaine (p less than 0.01). Maximum decreases in blood pressures were 26 +/- 15% of control and occurred at 32 +/- 14 seconds after the injection of bupivacaine. The maximum decrease in heart rate was 38 +/- 16% and occurred at 13 +/- 10 seconds after the injection of bupivacaine. Maximum heart rate changes occurred significantly earlier than maximum decreases in CFR (p less than 0.01). On the other hand, maximum blood pressure changes occurred significantly later than maximum decreases in CFR (p less than 0.01). The data reported here demonstrate that conscious animals respond similarly to animals anesthetized with chloral hydrate with respect to the medullary effect of local anesthetics.

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