Ventilatory sensitivity to CO(2) in awake adult Brown Norway (BN) rats is 50-75% lower than in adult Sprague-Dawley (SD) and salt-sensitive Dahl S (SS) rats. The purpose of the present study was to test the hypothesis that this difference would be apparent during the development of CO(2) sensitivity. Four litters of each strain were divided into four groups such that rats were exposed to 7% inspired CO(2) for 5 min in a plethysmograph every third day from postnatal day (P) 0 to P21 and again on P29 and P30. From P0 to P14, CO(2) exposure increased pulmonary ventilation (Ve) by 25-50% in the BN and SD strains and between 25 to over 200% in the SS strain. In all strains beginning around P15, the response to CO(2) increased progressively reaching a peak at P19-21 when Ve during hypercapnia was 175-225% above eucapnia. There were minimal changes in CO(2) sensitivity between P21 and P30, and at both ages there were minimal between-strain differences. At P30, the response to CO(2) in the SS and SD strains was near the adult response, but the response in the BN rats was 100% greater at P30 than in adults. We conclude that 1) CO(2)-sensing mechanisms, and/or mechanisms downstream from the chemoreceptors, change dramatically at the age in rats when other physiological systems are also maturing ( approximately P15), and 2) there is a high degree of age-dependent plasticity in CO(2) sensitivity in rats, which differs between strains.
A series of phenethylamine derivatives with various ring substituents and with or without N-methyl and/or C-alpha methyl or ethyl groups was synthesized and assayed for their ability reversibly to inhibit monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B). Several compounds showed potent and selective MAO-A inhibitory activity (IC(50) in the submicromolar range) but none showed appreciable activity toward MAO-B. A three-dimensional quantitative structure-activity relationship study for MAO-A inhibition was performed on the series using comparative molecular field analysis (CoMFA). The resulting model gave a cross-validated q(2) of 0.72 and showed that in this series of compounds steric properties of the substituents were more important than electrostatic effects. Molecular modeling based on the recently published crystal structure of inhibitor-bound MAO-A provided detailed evidence for specific interactions of the ligands with the enzyme, supported by previous references and consistent with results from the CoMFA. On the basis of these results, structural determinants for selectivity of substituted amphetamines for MAO-A are discussed.
The biogenetic hypothesis that the Lycopodium alkaloids are modified dimers of pelletierine (2, 3) was tested experimentally in Lycopodiumtristachyum, Pelletierine is indeed incorporated into lycopodine, but only one pelletierine unit entered the alkaloid, rather than two units, as predicted. The hypothesis thus requires modification.Δ1-Piperideine serves as a specific precursor of lycopodine. Two Δ1-piperideine moieties are incorporated in such a way that the identity of C-2 and -6 of each of the precursor units is maintained.
Baccharis linearis Ruiz et Pav, Baccharis rbomboidalis Remy, and Baccharis solieri Remy (Compositae). The ethanolic extracts afforded a novel chromene 1 along with seventeen known compounds (Table 1).Chromenes are of common occurrence in the Compositae (1), and the methyl ester of compound 1 was recently reported from a Wemeria species (2). In addition to chromene 1, oleanolic acid, stigmasterol, ß-amyrin, and friedelinol were also present in varying amounts in the three Baccharis species (Table 1). EXPERIMENTAL Plant materials.-The plants were collected at the base of the mountains near Santiago, Chile, in October 1984. Voucher specimens are kept at the
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