@entity35 were taught to self-administer Leu-E (10, 25 and 100 micrograms/microliters) or Met-E (0.5, 10 and 100 micrograms/microliters) through a cannula implanted in the lateral cerebral ventricle (i.c.v.). Their self-injection behaviour was studied before, during and after nociceptive stimulation. In the course of the control period of the experiment, the @entity35 rapidly learned lever pressing for self-injection of @entity10971 but they did not increase their self-administration of Leu-E or Met-E during the nociceptive electrical stimulation period. Also studied were the acute effect of i.c.v. @entity10971 and @entity1286 on tail-flick latency (sec) and electrical threshold vocalization (mA). The analgesic effect of Leu-E and Met-E was of short duration (less than 2-6 min). The mean rise (i.e., analgesia) of the tail-flick threshold showed a significant difference after i.c.v. Met-E only. The acute i.c.v. effect of 20 or 30 micrograms of @entity1286 induced a long-lasting analgesia, greater than 40 min. These results show that Leu-E and Met-E are not rewarding during a nociceptive stimulus. This may be due to the short and inconstant analgesic action of i.c.v. enkephalins.

A study of intracerebroventricular self-administration of leucine or methionine @entity10971 by XXXX in response to intermittent electric shocks.

@entity35 :: ('10116', 'Species') :: ['Rats', 'rats'] @entity10971 :: ('29237(Tax:10116)', 'Gene') :: ['enkephalin'] @entity1286 :: ('MESH:D009020', 'Chemical') :: ['morphine']
@entity35 :: (10116,Species) :: ['rats']
