291
Preliminary
Communication
ENDOGENOUS OPIOID PEPTIDES
IN NEURONS OF THE HUMAN BRAIN
mation has been obtained in laboratory animals there are indications that opiate-like substances are present in the human brain.13 The present report describes the direct microscopical visualisation of .neurons in the human brain containing an opiate-like peptide, as revealed by
immunocytochemistry.
A. C. CUELLO MATERIALS AND METHODS
Medical Research Council Neurochemical Pharmacology Unit,
Department of Pharmacology, Medical School, Hills Road, Cambridge CB2 2QD Immunoreactive leucine-encephalin has been found in nerve terminals and cell bodies of neurons in the human brain. The most intense reaction was found in the globus pallidus, followed by the spinal nucleus of the trigeminal nerve. These observations suggest that in man endogenous opioid substances may play an important part in neurotransmission in areas of the central nervous system related to pain and locomotor activity.
Summary
INTRODUCTION
RECEPTORS to morphine have been well characterised in a variety of peripheral organs.1,2 The presence in the mammalian brain of receptors which respond specifically to opiates has also been proposed.3,4 These observations led to the speculation that mammalian brains produce an opioid substance as the natural ligand for such receptors. Hughes et al. demonstrated the existence of two brain pentapeptides, leucine-encephalin and methionine-encephalin, with opiate-like pharmacological actions which were blocked by morphine antagonists. Other opiate-like substances have been also described in the mammalian brain, and they, like Met-encephalin, correspond to 7different portions of the larger peptide p-lipotrophin. 6, Of all endogenous opiate-like substances, the encephalins seem to be the most abundant in the brain. They have been found by radioimmunoassay and immunocytochemistry,8-12 to be unevenly distributed in the central nervous system of laboratory animals. They are particularly concentrated in areas related to pain perception, but they are also found in the extrapyramidal system. Although the bulk of this infor-
obtained up to 32 h after death, and diffixed in cold 4% paraformaldehyde in 0.11 mol/I phosphate buffer (pH 7-0). Brains from Wistar adult male rats were also fixed by immersion or by intracardiac perfusion with the same fixative. The tissue samples were fixed for 2-4 h and kept for up to 5 days in the same phosphate buffer containing 5% sucrose. Sections 10 .m thick were obtained at - 20°C in a cryostat and stained with the indirect immunofluorescent technique.14 A rabbit leucine-encephalin antiserum prepared by Dr Richard Miller (Chicago University) was used in this study. This antiserum did not cross-react with p-Iipotrophin or the adrenocorticotrophic hormone. The cross-reactivity with methionine-encephalin was 1% and with &bgr;-endorphin
Preliminary
Communication
ENDOGENOUS OPIOID PEPTIDES
IN NEURONS OF THE HUMAN BRAIN
mation has been obtained in laboratory animals there are indications that opiate-like substances are present in the human brain.13 The present report describes the direct microscopical visualisation of .neurons in the human brain containing an opiate-like peptide, as revealed by
immunocytochemistry.
A. C. CUELLO MATERIALS AND METHODS
Medical Research Council Neurochemical Pharmacology Unit,
Department of Pharmacology, Medical School, Hills Road, Cambridge CB2 2QD Immunoreactive leucine-encephalin has been found in nerve terminals and cell bodies of neurons in the human brain. The most intense reaction was found in the globus pallidus, followed by the spinal nucleus of the trigeminal nerve. These observations suggest that in man endogenous opioid substances may play an important part in neurotransmission in areas of the central nervous system related to pain and locomotor activity.
Summary
INTRODUCTION
RECEPTORS to morphine have been well characterised in a variety of peripheral organs.1,2 The presence in the mammalian brain of receptors which respond specifically to opiates has also been proposed.3,4 These observations led to the speculation that mammalian brains produce an opioid substance as the natural ligand for such receptors. Hughes et al. demonstrated the existence of two brain pentapeptides, leucine-encephalin and methionine-encephalin, with opiate-like pharmacological actions which were blocked by morphine antagonists. Other opiate-like substances have been also described in the mammalian brain, and they, like Met-encephalin, correspond to 7different portions of the larger peptide p-lipotrophin. 6, Of all endogenous opiate-like substances, the encephalins seem to be the most abundant in the brain. They have been found by radioimmunoassay and immunocytochemistry,8-12 to be unevenly distributed in the central nervous system of laboratory animals. They are particularly concentrated in areas related to pain perception, but they are also found in the extrapyramidal system. Although the bulk of this infor-
obtained up to 32 h after death, and diffixed in cold 4% paraformaldehyde in 0.11 mol/I phosphate buffer (pH 7-0). Brains from Wistar adult male rats were also fixed by immersion or by intracardiac perfusion with the same fixative. The tissue samples were fixed for 2-4 h and kept for up to 5 days in the same phosphate buffer containing 5% sucrose. Sections 10 .m thick were obtained at - 20°C in a cryostat and stained with the indirect immunofluorescent technique.14 A rabbit leucine-encephalin antiserum prepared by Dr Richard Miller (Chicago University) was used in this study. This antiserum did not cross-react with p-Iipotrophin or the adrenocorticotrophic hormone. The cross-reactivity with methionine-encephalin was 1% and with &bgr;-endorphin
