Biomedical subjects
Publications and source records attributed to M C McNamara.
The concentrations of DOPA and 5 hydroxytryptophan in rat brain were decreased by freezing on dry ice rather than in liquid nitrogen, and by a 5 minute delay in removing and freezing the brain by either method. The effect of post-mortem delay in freezing was greater for 5 HTP than for DOPA.
Squirrels learned to escape from a water bath by making a visual discrimination. Twenty-four hours after reaching criterion for learned behavior, the animals were exposed to the first of two 11-day cold exposures. The animals that hibernated had better retention of the learned behavior.
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Treatment with the serotonin (5-HT) reuptake inhibitor zimelidine, 20 mg/kg/24 hr, SC, for 14 days increased the duration of vaginal cycles in 3 month-old Long Evans hooded rats. It induced persistent vaginal estrus in 12 of 16 ten-month-old animals, and blocked reinitiation of vaginal cycles by L-dopa in 10 of 10 twenty-month-old rats. A single injection of zimelidine at 1400 hr did not alter the vaginal smear pattern of young or middle-aged cycling females or old constant estrus females. Also, a single dose of zimelidine at 1400 hr on the day of vaginal proestrus had no effect on serum LH values in young females. The serotonergic neurotoxin 5,7-dihydroxytryptamine, 4 micrograms, injected into the ventral and dorsal raphe areas (after desipramine, 25 mg/kg IP) reinitiated vaginal cycling in 8 of 13 twenty-month-old rats. These results suggest that age-dependent changes in serotonin metabolism may contribute to the age-dependent changes in luteinizing hormone secretion which eventually lead to the cessation of ovarian function in the rat and that alterations in serotonin function are an important component of the mechanism by which treatments with catecholamine precursors reinstate ovarian function in the old female rat.