Dual effects of the lichen glucan PB-2, extracted from Flavoparmelia baltimorensis, on the induction of long-term potentiation in the dentate gyrus of the anesthetized rat: possible mediation via adrenaline beta- and interleukin-1 receptors.
We have previously found that oral or intravenous (i.v.) administration of the polysaccharide fraction PB-2, extracted from the lichen Flavoparmelia baltimorensis, facilitated the induction of long-term potentiation (LTP) in the dentate gyrus (DG) in vivo. In this study, the mechanism underlying the effect of PB-2 on the induction of LTP was investigated in the DG of anesthetized rat focusing on the contribution of the interleukin-1 (IL-1) receptor and the adrenaline beta-receptor. An i.v. injection of IL-1ra (10(-9) g/kg), an antagonist of the IL-1 receptor, had no effect on the basal response in the DG; however, this treatment augmented the enhancement of LTP induced by a single i.v. injection of PB-2 (10(-3) g/kg). This potentiating effect was also observed following intracerebroventricular (i.c.v.) injection of IL-1ra (10(-15)-10(-11) g). An i.v. injection of IL-1beta (3.5 x 10(-15)-3.5 x 10(-9) g/kg) inhibited the induction of LTP, which was diminished by the previous application of IL-1ra. These results suggest that the activation of the IL-1 receptor induces the suppression of LTP in PB-2-treated rats, and that endogenous IL-1beta contributes to the IL-1 receptor activation. An i.c.v. infusion of metoprolol (7.5 x 10(-6) g), an antagonist of the adrenaline beta(1)-receptor, attenuated the enhancement of LTP induced by an i.v. injection of PB-2. These results suggest that PB-2 has two different effects on the LTP, an enhancing effect and an inhibiting one, and that it exhibited the significant enhancing effect on the LTP as a total balance of these effects.
Edagawa
Yoshikuni
Y
Department of Pharmacology, College of Pharmacy, Nihon University, 7-7-1 Narashinodai, Funabashi, Chiba 274-8555, Japan. edagaway@pha.nihon-u.ac.jp
Sato
Fumiyuki
F
Saito
Hiroshi
H
Takeda
Tadahiro
T
Shimizu
Noriko
N
Narui
Takao
T
Shibata
Shoji
S
Ito
Yoshihisa
Y
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D018891:Dentate Gyrus / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1 / Q000494:pharmacology; D008011:Lichens / Q000737:chemistry*; D017774:Long-Term Potentiation / Q000187:drug effects* / Q000528:radiation effects; D008297:Male; D008790:Metoprolol / Q000494:pharmacology; D008955:Models, Cardiovascular; D010936:Plant Extracts / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D017472:Receptors, Interleukin-1 / Q000037:antagonists & inhibitors / Q000502:physiology*; D012795:Sialoglycoproteins / Q000494:pharmacology; D013997:Time Factors; D047071:beta-Glucans / Q000494:pharmacology*
D000319:Adrenergic beta-Antagonists; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D010936:Plant Extracts; D011943:Receptors, Adrenergic, beta; D017472:Receptors, Interleukin-1; D012795:Sialoglycoproteins; D047071:beta-Glucans; D008790:Metoprolol