ISSN:
1432-1912
Keywords:
Key words N-methyl-D-aspartate (NMDA)
;
Trans-4-hydroxy-(S)-pipecolic acid-4-sulfate (t-HPIS)
;
(2S
;
3R
;
4S) cyclopropylglutamate (L-CGA C)
;
(R
;
S)-(tetrazol-5-yl)-glycine (TG)
;
1-aminocyclobutane-cis-1
;
3-dicarboxylic acid (ACBD)
;
L-[3H] GLU binding
;
Myenteric plexus
;
Cortex
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Several potent and selective agonists of the glutamate (L-GLU) receptors of N-methyl-D-aspartate (NMDA) type have been tested on the L-[3H]GLU binding to rat cortical membranes, on the depolarization of mouse cortical wedges and on the contraction of guinea pig longitudinal muscle myenteric plexus preparations with the aim of comparing the NMDA receptors present in the cortex and those present in the gut. When the depolarization of the cortical wedges was evaluated, the EC5 0 values of the agonists were (μM): (R,S)-(tetrazol-5-yl)-glycine (TG) 0.3; trans-4-hydroxy-(S)-pipecolic acid-4-sulfate (t-HPIS) 0.7; 1-aminocyclobutane-cis-1,3-dicarboxylic acid (ACBD) 0.8; NMDA 8; (2S,3R,4S) cyclopropylglutamate (L-CGA C) 12; quinolinic acid (QUIN) 400. When the contraction of the longitudinal muscle myenteric plexus was evaluated, the EC5 0 values were (μM): L-CGA C 1; TG 8; ACBD 50; t-HPIS 100; QUIN 500 and NMDA 680. When the displacement of NMDA specific L-[3H]GLU binding from rat cortical membranes was evaluated, the IC5 0 values were (μM): L-CGA C 0.003; TG 0.005; ACBD 0.044; t-HPIS 0.062; NMDA 0.31 and QUIN 15. No significant correlation was found when the EC5 0 values obtained in the ileum were plotted against the EC5 0 values obtained in the cortex (r=0.47). In particular it was noted that L-CGA C was approximately three orders of magnitude more potent than NMDA when tested in the ileum but had a potency not significantly different from that of NMDA when tested in the cortex. On the contrary, t-HPIS was particularly potent in cortical wedges. The results of these experiments suggest that different populations of NMDA receptors are present in the tissues of the three mammalian species investigated. In particular, the receptors present in the mouse cortical wedges are selectively stimulated by t-HPIS while those present in the guinea pig myenteric plexus are preferentially stimulated by L-CGA C. Thus at least two functional subtypes of NMDA receptors may be identified in mammalian tissues by using the order of potency of selective agonists.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00169077
Permalink
