EXISTENCE OF CAPSAICIN-SENSITIVE GLUTAMATERGIC TERMINALS IN RAT HYPOTHALAMUS

CAPSAICIN has been suggested to act not only on thin primary afferents but also on the hypothalamus, but the neurotransmitter(s) of central capsaicin-sensitive neurons are unknown. The present study was conduct ed to determine whether any central, especially hypothalamic, glutamat ergic terminals were sensitive to capsaicin. Capsaicin evoked glutamat e release from slices of hypothalamus and lumbar dorsal horn, but not cerebellum. Such capsaicin action was Ca2+ dependent and inhibited by the capsaicin antagonist capsazepine. Vanilloid receptor subtype 1 mRN A was widely distributed in the brain, with a marked level in the hypo thalamus and cerebellum, but not in the spinal cord. The results sugge st that there are glutamatergic terminals sensitive to capsaicin in th e hypothalamus. (C) 1998 Rapid Science Ltd.