Neurotrophic action of VIP on spinal cord cultures.

Vasoactive intestinal peptide-like immunofluorescence was observed in 3-5% of the neurons in 4 week old dissociated cultures from fetal mouse spinal cord and dorsal root ganglion. Radioimmunoassay indicated that VIP was spontaneously released into the culture medium. This release was inhibited by tetrodotoxin (TTX). Previous studies indicated that 50-60% of the spinal cord neurons die between days 7 and 21 in vitro. Blockade of electrical activity with TTX during days 8-15 resulted in a 30% decrease in the number of neurons as compared to control cultures. Addition of VIP (0.1 nM) to TTX-treated cultures prevented neuronal cell death. When VIP alone was added to the cultures, no significant difference in the number of neurons from controls was observed. The possibility that VIP influences cholinergic neurons was tested by measuring choline acetyltransferase (CAT) activity at various periods during development. A 48 hour treatment with 0.1 nM VIP increased CAT activity by 50%. The CAT stimulation was observed only during a period in development when naturally occurring neuronal cell death was taking place. The increases in CAT activity were dose dependent within a range of 10(-12) M to 10(-10) M VIP; however, higher concentrations of VIP attenuated the increases in enzyme activity.