RESUMO
Recently histamine is being considered as an important neurotransmitter/neuromodulator in the central nervous system. This has been supported from the present observations with regard to thermoregulatory responses elicited following histamine administration into different CSF compartments. Administration of histamine into the right lateral cerebral ventricle of rats showed a dose dependent fall in rectal temperature. This hypothermic response was evident only at moderately low or at thermoneutral ambient temperature. Administration of histamine into fourth ventricle produced hypothermic response at low ambient temperature and hyperthermia at thermoneutral ambient temperature, which was no longer observed when the ambient temperature remained above the thermoneutral zone. Infusion of histamine into spinal subarachnoid space produced hyperthermia which developed very slowly. However, the infusion of histamine into the subarachnoid space around the brain stem did not exhibit any change in rectal temperature. The significance of these observations has been discussed.