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σ Receptor Modulation of Noradrenergic‐Stimulated Pineal Melatonin Biosynthesis in Rats
Author(s) -
Steardo L.,
Monteleone P.,
D'Istria M.,
Serino I.,
Maj M.,
Cuomo V.
Publication year - 1996
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1996.67010287.x
Subject(s) - melatonin , pineal gland , medicine , endocrinology , receptor , chemistry , receptor antagonist , biology , antagonist
Because σ receptors are richly concentrated in the rat pineal gland, the present study was performed to investigate their possible role in the modulation of melatonin production. To this purpose, we assessed in vivo the effects of the σ‐receptor ligands 1,3‐di(2‐tolyl)guanidine and (+)‐ N ‐allylnormetazocine on the rat pineal gland activity during either the daytime or the nighttime. Compared with vehicle, 1,3‐di(2‐tolyl)guanidine and (+)‐ N ‐allylnormetazocine potentiated the enhancement of N ‐acetyltransferase activity and pineal melatonin content induced by isoproterenol administration during the daytime, whereas they did not affect the diurnal basal biosynthetic activity of the gland. Conversely, at night, 1,3‐di(2‐tolyl)guanidine and (+)‐ N ‐allylnormetazocine enhanced significantly the physiological increases in both pineal N ‐acetyltransferase activity and melatonin levels. This enhancement was prevented by pretreatment with rimcazole, a specific σ‐receptor antagonist. These findings suggest that, in rats, the activation of pineal σ‐receptor sites does not affect the biosynthetic activity of the pineal gland during daytime, whereas it pontentiates the production of melatonin when the gland is noradrenergically stimulated either by isoproterenol administration or by the endogenously released norepinephrine at nighttime.