title: Relative potency of synthetic analogs of Ptychodiscus brevis toxin in depressing synaptic transmission evoked in neonatal rat spinal cord in vitro.
abstract: Effects of Ptychodiscus brevis toxin (PbTx) analogs on the spinal synaptic transmission in neonatal rats in vitro were evaluated. PbTx1/PbTx2 had aromatic groups and PbTx3/PbTx4 had aliphatic groups. All the analogs depressed monosynaptic reflex (MSR) and polysynaptic reflex (PSR) in a concentration-dependent manner. The maximal depression of MSR (75% from initial) and PSR (96%) was at 84 microM for PbTx1. Concentration to produce 25% inhibition from initial (IC25) by PbTx1 for MSR and PSR was < or =2.8 microM. The maximal depression of MSR (80%) was at 96 microM and PSR (100%) was at 32 microM by PbTx2. IC25 for MSR and PSR were 5.5 microM and <3.2 microM, respectively. PbTx3 decreased MSR by 25% maximally (=IC25) at 36 microM. The depression of PSR fluctuated and was maximal (75%) at 108 microM and IC25 was 6.2 microM. PbTx4 depressed MSR and PSR at the maximum of 35% at 32 microM and IC25 for MSR was 8.3 microM and for PSR was 35 microM. Rank order of potency of toxins for depressing MSR was PbTx1>PbTx2>>PbTx4>PbTx3; and for PSR it was PbTx2>PbTx1>PbTx3>>PbTx4. Results indicate that the toxins having aromatic groups exhibited greater neurotoxicity.
authors.affiliation: Department of Physiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi 221005, India.
authors.forename: J N
authors.initials: JN
authors.lastname: Singh
authors.forename: S
authors.initials: S
authors.lastname: Das Gupta
authors.forename: A K
authors.initials: AK
authors.lastname: Gupta
authors.forename: S N
authors.initials: SN
authors.lastname: Dube
authors.forename: S B
authors.initials: SB
authors.lastname: Deshpande
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D003864:Depression, Chemical; D004141:Dinoflagellida / Q000737:chemistry / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008387:Marine Toxins / Q000633:toxicity*; D035964:Oxocins; D051381:Rats; D013116:Spinal Cord / Q000187:drug effects* / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects*
chemical_list: D008387:Marine Toxins; D035964:Oxocins; C051732:Ptychodiscus brevis T2 toxin