The immediate effect of the neurotoxin on the postsynaptic neuron is to inhibit control over ion concentrations across the cell membrane. The neurotoxin blocks nervous transmission at synapses which prevents the vesicles containing the neurotransmitter from fusing with the presynaptic membrane so the information does not transfer from one neuron to another and as a result the body is present at constant relaxation mode. The membrane potential of postsynaptic neuron will decrease due to neurotoxin.
The primary consumers like rabbits or other small animals that are normally eaten by the secondary consumers (snakes) would over populate and eat all of the producers (plants) and the plants would die out. This would eventually lead to the decrease of the primary consumer (rabbit/small animals) population.