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Micromolar L-2-amino-4-phosphonobutyric acid selectively inhibits perforant path synapses from lateral entorhinal
Abstract:
Transverse slices of the rat hippocampus were used to examine the ability of phosphonate analogues of acidic amino acids to inhibit perforant path synaptic transmission. Micromolar concentrations of L-2-amino-4-phosphonobutyric acid (APB), an analogue of L-glutamic acid, inhibited transmission from the lateral entorhinal cortex. Two other less-sensitive components were detected in projections from the medial entorhinal cortex. The component from the lateral entorhinal cortex showed high stereospecificity for the L-isomer of APB and was relatively insensitive to phosphonate homologues of shorter and longer chain length.
Insights
L-2-amino-4-phosphonobutyric acid (APB), an L-glutamic acid analogue, inhibits synaptic transmission in rat hippocampus. This inhibition, particularly from the lateral entorhinal cortex, shows high stereospecificity for the L-isomer of APB.
Area of Science:
- Neuroscience
- Neuropharmacology
- Synaptic Plasticity
Background:
- The hippocampus plays a crucial role in learning and memory.
- Synaptic transmission in the hippocampus, particularly via the perforant path, is vital for information processing.
- Acidic amino acids are key neurotransmitters involved in excitatory synaptic transmission.
Purpose of the Study:
- To investigate the inhibitory effects of phosphonate analogues of acidic amino acids on perforant path synaptic transmission in rat hippocampus.
- To characterize the specificity and potency of L-2-amino-4-phosphonobutyric acid (APB) as an inhibitor.
Main Methods:
- Electrophysiological recordings from transverse slices of rat hippocampus.
- Application of phosphonate analogues, including L-APB, to assess inhibition of synaptic transmission.
- Analysis of stereospecificity and structure-activity relationships of APB analogues.
Main Results:
- Micromolar concentrations of L-APB significantly inhibited synaptic transmission originating from the lateral entorhinal cortex.
- Two less sensitive inhibitory components were identified in projections from the medial entorhinal cortex.
- The inhibitory effect from the lateral entorhinal cortex demonstrated high stereospecificity for the L-isomer of APB.
- APB showed relative insensitivity to phosphonate homologues of varying chain lengths.
Conclusions:
- L-APB is a potent inhibitor of perforant path synaptic transmission, particularly from the lateral entorhinal cortex.
- The findings suggest specific roles for different hippocampal pathways in response to acidic amino acid analogues.
- APB's stereospecificity offers insights into the structural requirements for inhibiting excitatory neurotransmission.