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B Thorne

Publications and source records attributed to B Thorne.

8 recordsLinked to original sources
PubMed1997

Modulation of hippocampal norepinephrine release by cholinergic agonists is altered by AF64A lesion.

The effect of lesioning hippocampal cholinergic neurons with the neurotoxin AF64A on the ability of cholinergic agonists to modulate stimulation-induced release of 3H-norepinephrine (NE) from rat hippocampal slices was studied. Rats received intracerebroventricular injections of either AF64A (ethylcholine mustard aziridinium, 2 nmol) or vehicle (sham operated). Six weeks after treatment, release of 3H-NE evoked by electrical stimulation (2 Hz, 2 min) in the presence or absence of cholinergic agonists and/or antagonists was measured. Activation of M2 receptors with oxotremorine (in the presence of the M1 antagonist pirenzepine) caused a small inhibition of NE release, which was abolished in hippocampi from AF64A-treated rats. The Kd for high-affinity binding of the selective M2 ligand [3H] AF-DX 384 was increased 10-fold in lesioned tissues. The M1 selective agonist McN-A-343 produced a significant enhancement of NE release, which was unchanged by AF64A lesion. Binding studies with [3H] pirenzepine showed no change in the affinity or number of M1 receptors. Nicotine also caused a significant enhancement of evoked NE release, but this effect was markedly reduced in tissues from AF64A-treated rats. AF64A treatment caused a twofold decrease in the number of [3H] nicotine binding sites. This study suggests that long-term lesion of hippocampal cholinergic neurons with AF64A alters the function of postsynaptic muscarinic M2 and nicotinic cholinergic receptors that modulate the release of NE in the hippocampus.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗
PubMed1995

Lesion with the neurotoxin AF64A alters hippocampal cholinergic receptor function.

The effect of selective lesion of cholinergic inputs to the hippocampus on the function of hippocampal cholinergic receptors was examined. Hippocampal cholinergic neurons were lesioned in the rat by administration of the selective cholinergic neurotoxin AF64A (ethylcholine mustard aziridinium). Cholinergic receptor function was examined by assessing the ability of cholinergic agonists and antagonists to modulate the evoked release of radiolabelled acetylcholine (ACh) from hippocampal slices. Nicotine enhanced release, with a bell-shaped dose-response curve. The dose-response curve and EC50 for nicotine was shifted 10-fold to the left in lesioned rats, suggesting an increased sensitivity to nicotine. However, there were no differences in either the number of affinity of nicotinic receptors as determined with binding studies. The muscarinic agonist oxotremorine inhibited the evoked release of ACh in control tissues, but had much less effect in AF64A-lesioned tissues. Binding to the M1 receptor subtype was not changed. However, the Kd for binding to the high affinity subtype of the M2 receptor was increased 10-fold, suggesting that the receptor has become less sensitive to stimulation. Loss of M2 function may allow an increase in the effect of stimulating nicotinic receptors that modulate ACh release.

Acetylcholine↗
PubMed1991

Diphenylhydantoin attenuates hypoxia-induced release of [3H]glutamate from rat hippocampal slices.

The ability of diphenylhydantoin (DPH) to prevent hypoxia-induced [3H]glutamate release was examined in perfused rat hippocampal slices. Hypoxia (25 min; 95% N2/5% CO2) caused a prolonged release of [3H]glutamate, which was reduced significantly if DPH (20 microM) was present from the beginning of the perfusion. Perfusion with oxygenated medium (reoxygenation) following hypoxia also caused a pronounced release of glutamate. A therapeutic concentration of DPH, added before, during, or after hypoxia, decreased this release of glutamate. These results suggest that DPH may protect against glutamate-mediated neurotoxicity associated with stroke.

Animals↗
PubMed1991

Isolation of hippocampal synaptosomes on Percoll gradients: cholinergic markers and ligand binding sites.

The S1 Percoll procedure, devised empirically for cortical tissue, provides highly purified, functionally viable synaptosomes on a four-step Percoll gradient. Here, for the first time, the procedure has been applied to rat hippocampus, and the gradient fractions have been analysed with respect to cholinergic markers and the synaptosomal index, lactate dehydrogenase. The presynaptic cholinergic markers choline acetyltransferase and [3H]choline uptake were most enriched in fraction 4. In contrast, acetylcholinesterase activity was broadly distributed across the gradient, consistent with the separation of synaptic plasma membranes (in fractions 1 and 2) from synaptosomes (in fractions 3 and 4). This is supported by the recovery of muscarinic binding sites labelled with [3H]quinuclidinylbenzilate in fractions 1 and 2. (-)-[3H]-Nicotine binding sites, however, were most enriched in fraction 4, consistent with their predominantly presynaptic localisation in the CNS. These results demonstrate the applicability of the S1 Percoll method to discrete brain regions for the recovery of homogeneous and viable synaptosome fractions. The separation of presynaptic terminals from post-synaptic membranes is a further advantage of this technique.

Acetylcholinesterase↗