Effect of electrical stimulation of the mamillary nuclei of the hypothalamus on skin vessel permeability in intact and capsaicin-treated rats.

Stimulation of the mamillary nuclei of the rat hypothalamus induced increases in the permeability of forelimb skin microvessels. This effect was not seen in rats stimulated after administration of capsaicin at a dose (150 mg/kg) sufficient to deplete vasoactive neuropeptides from the peripheral nerve terminals of capsaicin-sensitive neurons. These data indicate a role for the mamillary nuclei in central mechanisms modulating the effector functions of primary capsaicin-sensitive neurons.

Effect of lesion of the hypothalamic mamillary nuclei on skin blood vessel permeability in normal and capsaicin-pretreated rats.

Contralateral increased exudation of plasma proteins, as measured by Evans Blue leakage into the fore paws, was produced by unilateral electrocoagulation of the mamillary nuclei in rats. Ten days after adult capsaicin pretreatment (increasing doses/4 days total 200 mg/kg, s.c.

Trophic functions of primary sensory neurons: are they really local?

The results of the present study, in the rat and cat, indicate that not only a lesion of peripheral nerve or capsaicin pretreatment but also pharmacological deafferentation with local anaesthetic or disruption of the connections between primary sensory neurons and the central nervous system are effective in producing dystrophic changes in tissues. These effects of deafferentation do not seem to depend on the sympathetic or parasympathetic efferents. Dystrophic changes are connected with microcirculation disturbances: slow down of local blood flow, elevation of the vascular permeability, oedema and leucocyte infiltration.

Neuroparalytic keratitis and capsaicin.

Subcutaneous injection of 50 mg/kg capsaicin to newborn rats resulted in a marked decrease of heat pain sensitivity and neurogenic inflammation. There was, however, no significant difference between capsaicin-pretreated and control rats in the severity of neuroparalytic keratitis after surgical deafferentation of the eye. Retrobulbar injection of 100 microliters of 0.