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17 Neuropeptide I General

THE IN SITU RELEASE OF IMMUNOREACTIVE SOMATOSTATIN FROM THE RABBIT SPINAL DORSAL HORN EVOKED BY NOXIOUS HEAT STI~IULI

MASAMICHI SATOH, YASUSHI KURAISHI*, NAOYOSHI HIROTA*, HARUKAZU SUZUKI* and IIIROSHI TAKAGI, Department of Pharmacology, Faculty of Pharma- ceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606, Japan

We previously reported that the in situ release of immmoreactive substance P (iSP) from the rabbit dorsal horn was increased by noxious mechanical, but not thermal, stimuli. In the present experiments, the effects of various types of natural stimuli in the periphery and morphine on the in situ release of inTnuno- reactive sc~atostatin(iSST) from the dorsal horn were studied in rabbits with similar in situ perfusion methods. The superficial dorsal horn of lumbar en- largement of the male rabbit decerebrated under pentobarbital anesthesia was perfused with artificial cerebrospinal fluid using a push-pull eannula system. Perfused sanples(l.0 ml) were oollected at 20-min intervals and assayed by radioirm~noassay for SST. Noxious thermal stimuli(ra~nt heat unilaterally applied to the skin of hind leg) increased the release of iSST from the ipsi- lateral dorsal horn but not from the contralateral one. The increase was Ca z+- dependent. Noxious mechanical (pinching a fold of skin), cold(putting a piece of ice on the skin) and innocuous(jetting air to the skin) stimuli did not alter the iSST release. Syst~nic morphine(10 mg/kg sc) inhibited the heat-evoked iSST release without affecting the spontaneous one. The inhibitory effect of morphine was diminished by locally applied naloxone(50 ~M) and methysergide(50 ~M) but not prazosin(50 ~M).

These results suggest that on the contrary to iSP, iSST may be released from the terminals of the thermo-, but not mechano-, nociceptive primary afferents, and that the serotonergic, but not noradrenergic, system in the spinal cord is probably involved in the inhibitory action of syst6mic morphine on the heat- evoked iSST release.

THE REGIONAL DISTRIBUTION OF NEUROPEPTIDES IN THE CEREBRAL CORTEX OF THE MACAQUE MONKEY

MOTOHARU HAYASHI and KIYOSHI OSHIMA~ Primate Research Institute, Kyoto University, Kanrin, Inuyama, Aichi 484, Japan

The regional distribution of vasoactive intestinal polypeptide (VIP), somatostatin (SRIF) and substance P (SP) was determined in the cortical subdivision of 4 adult Japanese monkeys (Macaca fuscata fuscata) by specific radioimmunoassays. The highest VIP level occured in the postcentral gyrus (136.9±23.8 fmol/mg pro- tein), and the lowest level was found in the occipital cortex (46.2±11.4 fmol/mg protein). The concentration in the association cortex, prefrontal, parietal and temporal cortex ranged between 50.6 and 90.7 fmol/mg protein. On the other hand, SRIF levels were higher in the association cortex (601.5-752.4 fmol/mg protein) than in the premotor, precentral gyrus and postcentral gyrus (379.4-432.6 fmol/mg protein). The highest value of SRIF was found in the amygdala (2338.6±203.8 fmol/mg protein), and the lowest level was found in the occipital cortex (135.5±11.2 fmol/mg pro- tein). As for SP, the highest concentration occured in the amyg- dala (389.1±90.7 fmol/mg protein). Among the cortex, the temporal lobe, superior temporal gyrus (131.2±27.1 fmol/mg protein) and anterior inferotemporal cortex (179.5±29.5 fmol/mg protein) showed about 2-3 times higher levels than in the precentral gyrus (56.5 ±9.1 fmol/mg protein) and postcentral gyrus (63.4±10.8 fmol/mg protein). The levels in the dorsolateral prefrontal cortex and orbital prefrontal cortex were 86.9±9.4 fmol/mg protein and 82.6±7.9 fmol/mg protein, respectively.