Enkephalinergic System Research Articles

Relationships between the catecholaminergic and enkephalinergic systems demonstrated by a combined technique of formaldehyde-induced fluorescence and immunocytochemistry

A technique for the localization of catecholamines and enkephalin in the same tissue section is described. Sections from rat brains prepared according to the Falck-Hillarp technique were examined by dark field fluorescence microscopy and then processed for immunocytochemistry for leucine-enkephalin (leu-enk) using the unlabeled antibody technique. In the medial hypothalamus the distribution of the catecholamines and enkephalin is complementary, while in the lateral hypothalamus the patterns are similar but not identical. Enkephalin terminals are also observed in and around the locus coeruleus, while enkephalin cell bodies are adjacent to the nucleus.

Behavioural dissociation of the enkephalinergic systems of nucleus accumbens and nucleus caudatus

The intracranial bilateral injection of naltrexone (0.5 μg) blocks analgesia and catalepsy elicited by morphine (15 mg/kg s.c.) when the opiate antagonist is injected in the N. accumbens. The injection of naltrexone in the N. caudatus and globus pallidus failed to modify the analgesia and catalepsy. The injection of morphine (22.5 μg) into the N. accumbens causes catalepsy and analgesia; the injection of the same dose of morphine into the N. caudatus is without any effect.