1.Acute effects of lead at central synapses in vitro.
Spence I, Drew C, Johnston GA, Lodge D. Brain Res. 1985 Apr 29;333(1):103-9.
The acute effects of lead in the rat CNS in vitro were studied on synaptic transmission in the isolated hemisected spinal cord from newborn rats and on the transport of exogenous GABA, acetylcholine and cis-3-aminocyclohexane carboxylic acid (ACHC) from slices of cerebral cortex from adult rats. Lead had quite variable effects on monosynaptic reflexes and synaptic potentials. When it occurred, the depression of synaptic transmission by lead (typically at 18.5 mumol/liters of added lead acetate) was reversible provided exposure times were less than 15 min; furthermore, depression could be antagonised by increasing the external calcium concentration. Lead had no effect on the postsynaptic responses of motoneurons to the putative transmitters L-glutamate, GABA and glycine or to eledoisin-related peptide. The effects of lead on uptake and release of exogenous GABA and ACHC were dependent on the perfusion buffer employed: minimal effects were seen in solutions buffered with either phosphate or carbonate.
2.Uptake inhibitors potentiate gamma-aminobutyric acid-induced contractile responses in the isolated ileum of the guinea-pig.
Ong J. Br J Pharmacol. 1987 May;91(1):9-15.
The gamma-aminobutyric acid (GABA)-induced contractile responses in the guinea-pig isolated ileum, maintained in Krebs-bicarbonate solution (pH 7.4, 37 degrees C), were significantly potentiated by inhibitors of GABA uptake, with a greater potentiation of the responses in the presence of (+/-)-cis-3-aminocyclohexane-carboxylic acid (ACHC) greater than L-2,4-diaminobutyric acid (DABA) greater than (+/-)-nipecotic acid greater than beta-alanine, whilst simultaneous addition of DABA with beta-alanine caused a greater potentiation of the GABA-induced responses than did nipecotic acid with beta-alanine, or any of the uptake blockers applied alone. The concentration-response curves for the GABA-induced ileal contraction were shifted to the left in the presence of the uptake inhibitors, this shift being more prominent over the lower concentration range of GABA (1-20 microM). By contrast, contractile responses to muscimol or 3-amino-1-propanesulphonic acid (3APS) were not potentiated by the uptake blockers, neither were their concentration-response curves altered.
3.Thrombin receptor-activating peptides (TRAPs): investigation of bioactive conformations via structure-activity, spectroscopic, and computational studies.
Ceruso MA1, McComsey DF, Leo GC, Andrade-Gordon P, Addo MF, Scarborough RM, Oksenberg D, Maryanoff BE. Bioorg Med Chem. 1999 Nov;7(11):2353-71.
The thrombin receptor (PAR-1) is an unusual transmembrane G-protein coupled receptor in that it is activated by serine protease cleavage of its extracellular N-terminus to expose an agonist peptide ligand, which is tethered to the receptor itself. Synthetic peptides containing the agonist motif, such as SFLLRN for human PAR-1, are capable of causing full receptor activation. We have probed the possible bioactive conformations of thrombin receptor-activating peptides (TRAPs) by systematic introduction of certain conformational perturbations, involving alpha-methyl, ester psi(COO), and reduced-amide psi(CH2N) scans, into the minimum-essential agonist sequence (SFLLR) to probe the importance of the backbone conformation and amide NH hydrogen bonding. We performed extensive conformational searches of representative pentapeptides to derive families of putative bioactive structures. In addition, we employed 1H NMR and circular dichroism (CD) to characterize the conformational disposition of certain pentapeptide analogues experimentally.
4.Role of the ventromedial nucleus of the thalamus in motor behaviour--I. Effects of focal injections of drugs.
Starr MS, Summerhayes M. Neuroscience. 1983 Dec;10(4):1157-69.
An assortment of drugs was injected into one or both ventromedial nuclei of the thalamus, to see how these influenced stereotypy, locomotion and posture in spontaneously behaving and actively rotating rats. Unilateral intrathalamic muscimol promoted weak ipsiversive circling, while bilateral treatment gave catalepsy. Similar injections of 4-amino-hex-5-enoic acid, which inhibits gamma-aminobutyrate metabolism, raised gamma-aminobutyrate levels in the ventromedial nuclei more than three-fold yet had none of these behavioural effects. The indirectly acting gamma-aminobutyrate agonists flurazepam and cis-1,3-aminocyclohexane carboxylic acid had little effect on posture and locomotion and, like muscimol and 4-amino-hex-5-enoic acid, elicited only very weak stereotypies. Procaine behaved like the gamma-aminobutyrate antagonist bicuculline, provoking vigorous locomotor hyperactivity and teeth chattering if given uni- or bilaterally. Pretreatment of one ventromedial nucleus with muscimol or 4-amino-hex-5-enoic acid, and to a lesser extent flurazepam or cis- 1,3-aminocyclohexane carboxylic acid, gave rise to pronounced ipsilateral asymmetries when combined with a large systemic dose of apomorphine.