Galanin-(1-15), but not galanin-(1-29), modulates 5-HT1A receptors in the dorsal hippocampus of the rat brain: possible existence of galanin receptor subtypes.
The aim of the present study was to evaluate whether galanin-(1-29) and galanin-(1-15) can modulate the 5-hydroxytryptamine1A (5-HT1A) receptors using [3H]8-OH-2-(di-n-propylamino)-tetralin ([3H]8-OH-DPAT) as a radioligand. Membrane preparations of the dorsal hippocampus, an area having the recently described [125I]galanin-(1-15) fragment binding sites, but having very few porcine [125I]galanin-(1-29) binding sites, were used. Galanin-(1-15) produced a concentration-dependent increase in the Kd value of [3H]8-OH-DPAT with a maximum effect of approximately 65% at 3 nM of galanin-(1-15), whereas galanin-(1-29) had no effect. This increase of the Kd value of [3H]8-OH-DPAT could be completely counteracted by the putative galanin antagonist M35 (1 nM). The Bmax values of [3H]8-OH-DPAT were not affected in any experiment. In conclusion, the present results give further evidence for the existence of a galanin receptor subtype mainly recognizing N-terminal galanin fragments, also having the ability to reduce the affinity of 5-HT1A receptors.
Hedlund
P B
PB
Department of Neuroscience, Karolinska Institute, Stockholm, Sweden.
Finnman
U B
UB
Yanaihara
N
N
Fuxe
K
K
D000818:Animals; D019004:Galanin; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology*; D010455:Peptides / Q000378:metabolism / Q000494:pharmacology*; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D044088:Receptors, Galanin; D011964:Receptors, Gastrointestinal Hormone / Q000378:metabolism*; D011985:Receptors, Serotonin / Q000187:drug effects*
D010446:Peptide Fragments; D010455:Peptides; D044088:Receptors, Galanin; D011964:Receptors, Gastrointestinal Hormone; D011985:Receptors, Serotonin; C086813:galanin (1-15); D019004:Galanin