Journal of Neuroscience, Vol 3, 2414-2419, Copyright © 1983 by Society for Neuroscience
Modulation by vasoactive intestinal peptide (VIP) of serotonin receptors in membranes from rat hippocampus
WH Rostene, CT Fischette and BS McEwen
The vasoactive intestinal peptide (VIP) has been located in various
structures of the rat brain, but few actions of the peptide have been
reported as yet. Because VIP might interact with classical neurotransmitter
systems in the central nervous system as it does in the periphery, we
investigated whether VIP can modulate serotonin (5- HT1) receptors in
membrane preparations obtained from brain areas which contain various
amounts of VIP and 5-HT receptors. The presence of bacitracin alone, which
protects VIP from proteolytic degradation, decreases the affinity of
[3H]5-HT binding in almost all of the structures tested. Scatchard analysis
indicates that, in the presence of bacitracin, VIP significantly decreases
the affinity and increases the number of specific high affinity binding
sites for [3H]5-HT in the dorsal hippocampus. VIP induces a dose-dependent
increase in the number of 5-HT1 receptors with a maximal response of 60%
with 10(-7) M VIP. At the same concentration, neither secretin nor glucagon
modifies 5-HT1 receptor density. No effect of VIP is observed in the
ventral hippocampus, parietal cortex, whole hypothalamus, and midbrain.
This effect of VIP is not observed when bacitracin is omitted, and the
presence of calcium ions does not alter the efficacy of the VIP effect. No
effect of VIP is obtained on [3H]spiperone binding assayed with 10 microM
mianserin to define specific binding. The present data suggest that some of
the effects of 5-HT in the hippocampus may be modulated by VIP.