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T Durkin

Publications and source records attributed to T Durkin.

26 records · Page 2Linked to original sources
PubMed1980

Changes in hippocampal cholinergic activity following learning in mice.

A short bar-press operant conditioning acquisition session with food reward on continuous reinforcement was shown to induce a decrease (13.5%) of hippocampal choline acetyltransferase activity in mice. Such an effect seems to be specific to this kind of learning since no change was observed in several control groups, including a group of mice submitted to another type of conditioning in the same apparatus. It is suggested that these enzymatic modifications might be responsible for the delayed improvement of performance observed on retention of this task.

Acetylcholinesterase↗
PubMed1979

Cholinergic involvement in ethanol intoxication and withdrawal-induced seizure susceptibility.

The enzymes of the cholinergic system have been investigated in discrete brain areas in alcohol-dependent rats, which were still intoxicated or were undergoing withdrawal. The ethanol intoxication resulted in a slight, but significant increase in choline acetyltransferase (CAT) activity in the caudate nucleus both 1 and 7 h after the last dose of ethanol. We also found a significant decrease in CAT activity in the temporal limbic cortex while rats were highly intoxicated. All other brain regions investigated, e.g., cerebellum, pons-medulla, frontoparietal cortex, hypothalamus and septum showed unchanged CAT activity. Rats were also analysed immediately following the onset of a withdrawal-induced audiogenic convulsive seizure where, in addition to the striatum, depressed CAT activity was observed in the hippocampus. In all the analysed situations acetylcholinesterase activity remained unchanged. These results show that ethanol intoxication leads to a perturbation in the synthetic capacity of acetylcholine in certain defined brain structures and that this may have some correlation to the observed behavioural impairments.

Acetylcholinesterase↗
PubMed1977

Regional acetylcholine turnover rates in the brains of three inbred strains of mice: correlation with some interstrain behavioural differences.

The hypothesis that the genetically determined behavioural differences which exist between the inbred mouse strains Balb/c, DBA/2 and C57Bl/6 may be related to differences in acetylcholine metabolism in certain regions of the brain has been tested. In vivo ACh turnover rates have been measured in three regions (hippocampus, caudate nucleus and frontal-parietal cortex) of the brains of each strain by following the rate of formation of labelled ACh, in these regions, after a pulse intravenous injection of a tracer dose of 3H labelled choline. Focused microwave procedures were used for the rapid fixation of brain tissue and Ch and ACh radioactivities were determined following their electrophoretic separation. Steady-state concentrations of Ch and ACh were measured by a sensitive radio-enzymatic method. Significant interstrain differences in ACh turnover rates are reported for each of the brain regions studied with the order of metabolic activity being Balb/c greater than DBA/2 greater than C57 Bl/6 in each case. These results are interpreted as being in agreement with previous reports on correlations between learning ability or locomotor activity and regional activities of choline acetyltransferase in the brains of these inbred strains. The correlations between the in vivo ACh turnover rates and (1) interstrain differences in behavioural measures and (2) regional choline acetyltransferase activities are discussed.

Acetylcholine↗
PubMed1977

Effects of hippocampal electrical stimulation on longterm memory and on cholinergic mechanisms in three inbred strains of mice.

Two sets of experiments have been carried out in an attempt to determine the role of hippocampal cholinergic mechanisms in a long-term memory storage. Three inbred strains of mice were presented with two different learning tasks in order to estimate their long-term retention abilities as well as changes in this ability after a post-trial hippocampal stimulation. In parallel experiments the enzymes involved in acetylcholine metabolism were studied under different experimental conditions. Our results indicate: (a) The capacity for long-term memory of the BALB/c line is much greater than that of either the C57BL/6 or C57BR strain. (b) Hippocampal post-trial electrical stimulation leads to an improvement of this capacity in the BALB/c strain. This phenomenon is less pronounced in C57BL/6 and non-existent in C57BR mice. (c) Choline acetyltransferase activity in the hippocampus is significantly higher in BALB/c than in the other two strains. In BALB/c this enzyme activity is greatly changed by the post-trial stimulation whereas in the C57BL/L strain only a slight variation of enzyme activity is observed. No modification occurs in C57BR. The results suggest that the more active acetylcholine synthesizing enzyme in the hippocampus of BALB/c may be related to a greater acetylcholine availability, thus favoring the establishment of a long-term memory, perhaps by releasing greater amounts of acetylcholine in the hippocampus immmediately after the learning session. The electrical stimulation of the hippocampus acts to magnify or accelerate this phenomenon. It is suggested that the efficiency of the stimulation would be related to the genetically determined higher cholinergic activity of the hippocampus.

Acetylcholine↗