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Biomedical subjects

R D Sewell

Publications and source records attributed to R D Sewell.

68 records · Page 4Linked to original sources
PubMed1981

Modification of convulsive behaviour and body temperature in mice by intracerebroventricular administration of prostaglandins, arachidonic acid and the soluble acetylsalicylic acid salt lysine acetylsalicylate.

The effects of centrally injected prostaglandins (PGE1 and PGF2 alpha), arachidonic acid and lysine acetylsalicylate were examined on the seizure activity and temperature changes produced by pentylentetrazole (PTZ) and also on maximal electroshock (MES) seizures. PGE1 antagonised both PTZ and MES seizures whilst PGF2 alpha had the reverse effect. In addition both PGs alone produced hyperthermia but attenuated PTZ hypothermia. Arachidonic acid protected against PTZ--but potentiated MES--seizures whilst lysine acetylsalicylate augmented the effects of both convulsive stimuli. Lysine acetylsalicylate and arachidonic acid alone were transiently hyperthermic and also antagonised PTZ hypothermia though the total net effect may have been due to a functional antagonism. It is suggested from these findings that PGE1 has anticonvulsant effects whilst PGF2 alpha promotes seizures neither of these properties correlating with thermoregulatory actions.

Animals↗
PubMed1980

Opiate receptors, endorphins and drug therapy.

A number of opioid peptides isolated from brain and peripheral tissue have been identified, and several types of opiate receptor postulated for these endogenous substances. In this study the effects of pharmacological manipulation of 5-hydroxytryptamine (5-HT) on the antinociceptive activity of morphine and two synthetic enkephalin analogus (D-ala2-leu-enkephalin and D-ala2-met-enkephalin) were investigated in mice and rats. Centrally injected 5-HT and peripheral clomipramine pretreatment potentiated both morphine and synthetic enkephalin analgesia whilst peripheral doses of cyproheptidine, lesions in the dorsal medial raphe (DMR) and reserpine pretreatment attenuated opioid analgesia. In the reserpine-pretreated group, centrally injected 5-HT restored the antinociceptive activity of morphine and D-ala2-leu-enkephalin. These results are discussed with respect to clomipramine therapy.

Analgesics↗
PubMed1975

Anti-nociceptive activity of narcotic agonists and partial agonists in mice given biogenic amines by intracerebroventricular injection.

Using a tail immersion technique in mice, the anti-nociceptive activity of some narcotic agonists (diamorphine, etorphine, morphine and pethidine), partial agonists (cyclazocine, nalorphine and pentazocine) and naloxone have been determined alone, and after the intracerbroventricular (ICV) injection of 5-hydroxytryptamine (5-HT) or noradrenaline (NA). In common with morphine, the anti-nociceptive effects of each agonist and partial agonist studied were significantly increased by ICV 5-HT, and significantly attenuated by ICV NA. The marginal anti-nociceptive activity of naloxone was not significantly affected by the ICV injection of either amine. It is concluded that the anti-nociceptive effects of all narcotic agonist and partial agonist agents are determined by the balance within the brain of the activities of the two amines, 5-HT and NA.

Analgesia↗
PubMedDate not supplied

Possible role for endogenous opiates in the regulation of food intake in the newborn rat.

The possible role of endogenous opiates in the regulation of food intake was investigated by studying their influence on body weight of rat pups. Subcutaneous injection of the opiate antagonist Mr 1452 to non-deprived 1 day old rats (1-4 mg/kg) and 1.5 hr deprived 5 day old rats (2-8 mg/kg) inhibited feeding. Its stereoisomer Mr 1453 increased intake when injected to nondeprived 1 day old rats (1-4 mg/kg), but was ineffective in altering feeding behavior in 1.5 hr deprived 5 day old rats (2-8 mg/kg). Subcutaneous injection of another opiate antagonist, levallorphan (6 and 9 mg/kg), to 3 hr deprived rats also decreased intake, while its stereoisomer dextrallorphan (3-9 mg/kg) was inactive in the same experimental conditions. Subcutaneous injection of the opiate agonist met5enkephalin (16 and 32 mg/kg) to 1.5 hr deprived 5 day old rats increased feeding but leu5enkephalin (8 and 16 mg/kg) did not alter feeding behavior in the same condition. Taken together, these findings suggest a role for endogenous opiates in the facilitation of feeding in the newborn rat.

Animals↗