Marilyn Morehead

α-phenyl-tert-butyl-nitrone inhibits free radical release in brain concussion

Traumatic brain injury (TBI) is one of the important causes of mortality and morbidity. The pathogenesis of the underlying brain dysfunction is poorly understood. Recent data have suggested that oxygen free radicals play a key role in the primary and secondary processes of acute TBI. We report direct electron spin resonance (ESR) evidence of hydroxyl (.OH) radical generation in closed-head injury of rats. Moderate brain concussion was produced by controlled and reproducible mechanical, fixed, closed-head injury. A cortical cup was placed over one cerebral hemisphere within 20 min of the concussion, perfused with artificial cerebrospinal fluid (aCSF) containing the spin trap agent pyridyl-N-oxide-tert-butyl nitrone (POBN, 100 mM), and superfusate samples collected at 10 min intervals for a duration up to 130 min post brain trauma. In addition, POBN was administered systemically (50 mg/kg body wt.) 10 min pretrauma and 20 min posttrauma to improve our ability to detect free radicals. ESR analysis of the superfusate samples revealed six line spectra (alpha N = 15.4 G and alpha beta H = 2.5 G) characteristic of POBN-OH radical adducts, the intensity of which peaked 40 min posttrauma. The signal was undetectable after 120 min. Administration of alpha-phenyl-tert-butyl-nitrone (PBN), a spin adduct forming agent systemically (100 mg/kg body wt. IP 10 min prior to concussion) alone or along with topical PBN (100 mM PBN in aCSF), significantly (p < 0.001) attenuated the ESR signal, suggesting its possible role in the treatment of TBI.

Cerebrovascular permeability and cognition in the aging rat

Regional cerebrovascular permeability-capillary surface area products (rPS) and brain vascular space (BVS) were measured in aging, conscious, unrestrained Sprague-Dawley rats. Three groups of animals were examined: young-mature (6 months), middle-aged (12-14 months), and old (24-26 months) rats. Complex maze learning had been previously characterized in these same animals. Maze learning declined with age. Brain vascular space did not differ significantly with age in any brain region. However, small, but significant age-dependent decreases in rPS (25-33%) were observed. These decreases occurred mainly in the old animals in the basal ganglia and parietal cortex, and in the middle-aged and old rats in the olfactory bulbs. Significant and unexpected positive average correlations between brain permeability-capillary surface area products (PS) and learning errors occurred primarily in young rats and were attributable mainly to changes in 5 of 14 brain regions; hypothalamus, hippocampus, parietal cortex, septal area and superior colliculus. The higher correlations between maze learning errors and PS in young animals may indicate dynamic regulation of this cerebrovascular parameter which is lessened with aging. Average correlations between PS and cerebral blood flow also were determined and found to be generally small and not significant for most brain regions and age groups.

Oxypurinol inhibits free radical release from the cerebral cortex of closed head injured rats.

Traumatic brain injury (TBI) is a significant cause of mortality and morbidity. Although the sequence of events underlying the resultant neuronal loss is still poorly understood, there are indications that oxygen-free radical generation is critically involved. Free radical generation in the cerebral cortex of closed head injury rats was monitored by measuring free radical release into cortical superfusates containing the spin trap agent 4-pyridyl-1-oxide-N-tert-butylnitrone (POBN, 100 mM). ESR analysis of the superfusates revealed six line spectra (alpha N = 15.4 G and alpha H beta = 2.5 G) characteristic of POBN-OH adducts. Administration of oxypurinol (40 mg/kg) 15 min prior to TBI prevented the formation of these radical adducts.

Alterations in CNS gene expression in a rodent model of moderate traumatic brain injury complicated by acute alcohol intoxication

The combined effects of acute alcoholic intoxication and moderate traumatic brain injury (TBI) on zif/268, glial fibrillary acidic protein (GFAP), and preproenkephalin (PPE) mRNA expression were examined. Adult male Wistar rats received ip injections of a 5% alcohol solution (2.4 g/kg in a final volume of 20 ml isotonic saline) 10 min prior to fixed-head, mechanical injury. Using Northern analysis, a transient three- to fourfold induction of zif/268 mRNA levels was observed 45 min after injury in both TBI and alcohol-treated rats. This induction occurred in regions close to the impact site, namely, the olfactory bulb (OB) and frontal cortex (FTCTX) but not in the more distal piriform/amygdala cortex (P/A). No PPE mRNA changes were observed at 45 min for any experimental group. By 6 h, zif/268 transcript levels returned to or fell below basal levels in the OB and FTCTX while GFAP mRNA levels began to increase in TBI rats. At 24 h, GFAP mRNA levels were greatly increased in all three brain regions of TBI rats. However, alcohol inhibited the temporal induction of GFAP mRNA in the FTCTX and P/A triggered by TBI at 6 and 24 h. These results suggest that although acute alcohol intoxication prior to TBI does not influence gene expression patterns immediately after injury, it may minimize the transcriptional activation of astrocytes particularly in more distant brain regions that were influenced by the impact in nonintoxicated rats.

Stress-Induced Suppression of the Prolactin Afternoon Surge in Ovariectomized, Estrogen-Treated Rats and the Nocturnal Surge in Pseudopregnant Rats Are Accompanied by an Increase in Median Eminence Dihydroxyphenylacetic Acid Concentrations

Experiments were performed to determine whether the suppression of prolactin (PRL) surges during restraint was accompanied by changes in the activity of tuberoinfundibular dopamine (TIDA) neurons in the median eminence. Animals were either ovariectomized and estrogen-treated (OVX-PEP) or cervically stimulated to induce pseudopregnancy (PSP). Restraint stress was administered by tying the hind legs together with plastic-coated bell wire. Animals were decapitated following 15 or 30 min of restraint stress or immediately after removal from the animal room (control) when PRL levels were basal (10.00 h), at the peak of the afternoon PRL surge in OVX-PEP animals (17.00 h) or the nocturnal PRL surge in PSP animals (05.00 h). Median eminence dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) were significantly decreased in control rats at 17.00 h when compared to control rats at 10.00 h (103.1 +/- 3.7 vs. 85.8 +/- 3.3 and 11.4 vs. 7.1 +/- 0.4 pg/micrograms protein, respectively) and plasma PRL was markedly elevated. Restraint stress at 10.00 h resulted in a significant increase in serum PRL, but this increase was not accompanied by a change in DA or DOPAC when compared to control animals (103.1 +/- 3.7 vs. 107.9 +/- 4.8 and 11.4 +/- 0.4 vs. 10.4 +/- 0.6 pg/micrograms protein, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

The restraint stress-induced decrease of the nocturnal prolactin surge and the physiology of pseudopregnancy and pregnancy in the rat

Experiments were performed to determine whether the restraint stress-induced decrease of the nocturnal prolactin (PRL) surge affected the length of pseudopregnancy (PSP) and/or the outcome of pregnancy in rats. Vaginal cycles were monitored daily and animals were electro-mechanically cervically stimulated on the morning of metestrus to induce PSP. Animals were restraint stressed by tying the hind legs together with plastic coated bell wire beginning on day 1 of PSP from 0100-0700h with reapplication of stress at 0400h for 6-9 days and then blood sampled for PRL and progesterone plasma levels. Restraint stress significantly decreased plasma PRL (P less than 0.001) and progesterone (P less than 0.05) levels. The length of PSP was significantly decreased (P less than 0.01) for restraint animals and for control animals that were blood sampled compared to control animals that were not sampled. In the pregnancy experiment, animals were mated upon arrival into the laboratory and assigned to one of four groups. For the restraint group, stress was initiated on day 1 of pregnancy as indicated by the presence of sperm in the vaginal lavage. Animals were stressed for 6-9 days for 6 hours during the nocturnal PRL surge as described above. One control group had no treatment; a second control group was sampled only, and a third control group was injected daily with pimozide, a dopamine antagonist, and stressed for 6-9 days. The group which received no treatment had significantly greater (P less than 0.05) incidence of successful pregnancy compared to the other 3 groups; there were no differences (P greater than 0.05) between the sampled, restraint and restraint + pimozide groups in the incidence of successful pregnancy. We conclude that restraint stress during the nocturnal PRL surge minimally affects the length of PSP and that the effect of stress on the outcome of pregnancy is not due to the decrease in nocturnal PRL surge.

The lack of a physiologic effect of the stress-induced decrease of the proestrous prolactin surge in the rat☆

Experiments were performed to determine whether the restraint stress-induced decrease in the proestrous prolactin (PRL) surge blocked luteolysis of the corpora lutea (CL), affected ovulation, or prevented the induction of pregnancy/pseudopregnancy in the next cycle. In all experiments rats were either stressed on proestrus and estrus, administered daily sc injections of 1 mg/day of 2-Br-alpha-ergocryptine (CB-154) for 4 days starting on diestrus II or not treated. In one experiment animals were sampled on the afternoon of proestrus to determine the effect of restraint stress on plasma PRL values and sacrificed on the morning of proestrus in the next cycle. Ovaries were removed, weighed, fixed and examined for number of CL. Restraint stress resulted in a significant increase in ovarian weight when compared to controls; CB-154 resulted in significant increases in ovarian weight when compared to stress and control animals. However, only CB-154-treated animals had a significant increase in the number of CL when compared to controls. In another experiment, animals were sacrificed on estrus of the next cycle and the oviducts examined for the number of ova. There were no differences among groups. In the final experiment, animals were placed with males of proven fertility on proestrus of the next cycle and examined for evidence of sperm in the vaginal lavage and/or vaginal plugs. CB-154 prevented the induction of pregnancy or pseudopregnancy due to a carry over effect of the drug on PRL surges. Restraint stress had no significant effect on the induction of pregnancy or pseudopregnancy. We conclude that there is no physiological significance to the stress-induced decrease of the proestrous PRL surge with respect to ovarian function or fertility.

Use of adrenocorticotrophic hormone analog to minimize brain injury

STUDY OBJECTIVES To investigate the effects of a vasoactive analog of adrenocorticotrophic hormone (GMM2) on time-dependent disturbances in regional cerebral blood flow, permeability-capillary surface area products, and intracranial pressure in a rat model of moderate concussion/brain injury. SETTING AND DESIGN Regional permeability-capillary surface area products and cerebral blood flow were measured at two hours after trauma. Intracranial pressure was monitored for 120 hours after trauma. SUBJECTS Male Wistar rats (330 to 430 g) (regional cerebral blood flow studies, n = 35; permeability-capillary surface area product studies, n = 36; intracranial pressure studies, n = 32). INTERVENTIONS Post-traumatic subcutaneous administration of nanomolar concentrations of GMM2 (31 nmol per rat). MEASUREMENTS AND MAIN RESULTS Untreated trauma acutely increased average brain permeability-capillary surface area products for sucrose and decreased average brain cerebral blood flow. Moreover, it produced marked and prolonged increases in intracranial pressure. Post-traumatic subcutaneous administration of nanomolar concentrations of GMM2 effectively reduced the early hypoperfusion, blood-brain barrier leakiness, and pathologic elevation of intracranial pressure. CONCLUSION Post-traumatic administration of GMM2, in nanomolar amounts, can prevent or reverse significantly the serious cerebrovascular sequelae of moderate head injury in this animal model. In view of its potency, low toxicity, and other neuroprotective properties, in both rats and human beings, these data suggest that GMM2 may have considerable clinical benefits in the treatment of central nervous system trauma.