M A Miguel Asai

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Several experiments have revealed an Endogenous Opioid System (EOS)-circadian rhythm. The brain-borne hormone, melatonin (MEL) has been shown to regulate the organism photoperiodic activity and may be implicated in the EOS-circadian rhythm. To explore this hypothesis, we studied the effect of functional pinealectomy on the EOS-circadian rhythm by measuring(More)
Established amygdaloid kindling causes an increase in the immunoassayable content of both Leuenkephalin and Met-enkephalin in the rat brain. Control and sham-operated (electrode implanted but not stimulated) rats do not show statistically significant differences in brain enkephalin content, while kindled rats show a 40% enkephalin increase in both(More)
Brain content of leucine-enkephalin and methionine-enkephalin changes independently during kindling of the amygdala. Both peptides were measured after 4, 8, 15 and 21 days of stimulation. Leu-enkephalin showed a progressive increase during the kindling: the results on the 4th day did not differ significantly from the controls, whereas those on the 8th day(More)
Wistar rats were injected daily with convulsant doses of PTZ (40 mg/kg). The brain content of immunoreactive (IR) enkephalins was measured after repetitive clonic convulsions and after the 'kindling' state was reached. In both instances we found a significant increase of IR [Leu5]enkephalin and IR [Met5]enkephalin in septum, striatum and amygdala 24 h after(More)
Pentylenetetrazol (PTZ) kindling was induced in male Wistar rats by daily i.p. injections of 40 mg/kg of the convulsant agent. IR-Met-enkephalin and IR-Leu-enkephalin were quantified in several brain regions 16 days after the last stimulus. In addition other rats received another PTZ dose on the sixteenth day and the samples were analyzed 1 and 24 h later.(More)
Possible relationships between dominance rank and brain methionine-enkephalin content were studied by using a method of consecutive rank determination in groups of mice reassembled according to their initial ordinal dominance rank. Thus, 10 groups of 3 Balb/c AnN mice of identical ordinal rank were formed with the consecutive dominants of 3 groups of 10(More)
Indirect evidence suggests that ejaculation might activate endogenous opioid systems, which exert an inhibitory influence on male rat sexual behaviour. The objective of the present study was to search for putative long-term changes in the contents of immunoreactive (IR) Met-enkephalin (IR-Met), Leu-enkephalin (IR-Leu) and opioid octapeptide(More)
Pentylenetetrazol (PTZ) kindling was induced in male Wistar rats (250-300 g) by daily intraperitoneal injections of 35 mg/kg of the convulsant agent. Immunoreactive (IR)-Met-enkephalin (IR-ME), IR-Leu-enkephalin (IR-LE), IR-heptapeptide (IR-HE), IR-octapeptide (IR-OC) and IR-synenkephalin (IR-Syn) in vitro release was measured from amygdala slices 24 h(More)
Penicillin-G has been used as a common agent to produce epileptic foci and interictal activity. The development of the interictal spikes has been associated with enhanced inhibitory effects. There is evidence that the opioid peptides play an important role in the production of some transient postictal behaviors. In order to test whether enkephalins are(More)
Using amygdaloid kindling in chronic rats, we were able to observe behavioral, electrographic and IR-Met- and IR-Leu-enkephalin changes throughout the progress of different stages of convulsive activity. Rats presenting the initial stages of kindling, rats presenting the first generalized motor seizure, and rats with at least 10 generalized seizures were(More)