Teruyuki Hirakawa

Inhibition of cerebral metabolic and circulatory responses to nitrous oxide by 6-hydroxydopamine in dogs

PurposeTo determine whether cerebral metabolic and circulatory consequences of N2O result from activation of the sympathoadrenal system. The effects of pretreatment with intracistemal injection of 6-OHDA, which produces chemical sympathectomy, were studied in dogs.MethodSeven days before measurement dogs were pretreated with intracisternal injection of either saline vehicle (sham-group) or 100 μg· kg−1 6-hydroxydopamine (6-OHDA group). Cerebral blood flow (CBF) was measured using an electromagnetic flow-meter probe and cerebral metabolic rate for oxygen (CMRO2) was calculated as the product of CBF and arterial-sagittal sinus blood oxygen content difference [C(a-v)O2].ResultsIn the sham group, N2O (60%) increased CMRO2 from 6.11 ± 0.21 ml· 100 g−1· min−1 to 7.10 ± 0.39 ml· 100g−1· min−1 and CBF from 63 ± 5 ml· 100 g−1 · min−1 to 173 ± 26 ml· 100 g−1· min−1. In the 6-OHDA group, CMRO2 did not change during N2O exposure, whereas CBF increased from 61 ± 3 ml· 100 g−1· min−1 to 135 ±19 ml· 100 g−1· min−1 but less then in the sham group. The 6-OHDA group displayed a reduction in cortical noradrenaline (NA) concentration from 263.2 ± 35.6 ng·g−1 to 102.7 ± 16.5 ng· g−1. Cortical dopamine (DA) concentration was not affected by 6-OHDA administration.ConclusionThese results suggest that most of the increase in CMRO2 and, at least a part of, the increase in CBF during N2O exposure in the sham-group are related to sympathoadrenal-stimulating effects of N2O.RésuméObjectifVérifier si les effets metaboliques et circulatoires cérébraux provoqués par l’inhalation de N2O résultent de l’activation du système sympathico-surrénalien. Au cours de cette étude, on a étudié sur des chiens les effets de la sympathectomie chimique provoquée par l’administration intracistemale de 6-OHDA.MéthodesD’abord, les chiens ont negu des injections intracisternaJes de sol. phys. (Groupe factice) ou de 100 μg· kg−1 de 6-hydroxydopamine (groupe 6-OHDA). Sept jours plus tard, le débit sanguin cérébral (DSC) a été mesuré à l’aide d’un débitmètre électromagnétique; le métabolisme cérébral pour l’oxygène (CMRO2) a été calculé en multipliant le DSC par la différence artério-sinus sagittal du contenu en oxygène [C(a-v)O2].RésultatsDans le groupe factice, le N2O (60%) a augmente le CRMO2 de 6,11 ± 0.21 ml· 100 g−1· min−1 à 7,10 ± 0,39 ml 100· g−1· min−1 et le DSC de 63 ± 5 ml· 100 g−1· min−1 à 173 ± 26 ml· 100 g−1· min−1. Dans le groupe 6-OHDA, le CMRO2 n’a pas varié pendant l’exposition au N2O, alors que le DSC augmentait de 61 ±3 ml· 100 g−1 · min−1 à 135 ± 19 ml· 100· g−1· min−1 mats moins que dans le groupe factice. Dans le groupe 6-OHDA, la concentration de la noradrenaline corticale baissait de 263,2 ± 35,6 ng· g−1 à 102,7 ± 16,5 ng·g−1, L’administration de 6-OHDA n’a pas affecté la concentration de la dopamine corticale.ConclusionCes résultats suggèrent que, dans le groupe factice, pendant l’exposition au N2O, la presque totalité de l’augmentation du CMRO2 et, au moins une partie de l’augmentation du DSC, sont causées par la stimulation sympathico-surrénalienne.

Increase in the threshold of pain and touch sensation in the human face with clonidine plus 30% nitrous oxide

OBJECTIVE This study was undertaken to assess the effects of clonidine combined with 30% nitrous oxide on tactile and pain sensations in the human face. STUDY DESIGN Thirty-three subjects were involved in the study. The subjects were divided into 4 groups: 100% oxygen with placebo; 30% N2O with placebo; 100% oxygen with clonidine (0.075 mg), and 30% N2O with clonidine. Three tests for the threshold of pain sensation and tactile sensation were made at 60 minutes before and 0, 15, and 30 minutes during N2O or O2 inhalation. RESULTS (1) The N2O with clonidine significantly increased the threshold of pain and tactile sensation in comparison with the other 3 treatments. (2) In terms of pain sensation, both N2O and clonidine showed significant increases in threshold of pain in comparison with the control values. CONCLUSIONS These results indicate that the analgesic effects of 30% nitrous oxide are enhanced when use of the gas is combined with prior clonidine administration.

2302 Modulation of synaptic transmission in mouse supraoptic neurons by opioid agonists

Shinji Hayashi’ , Makoto Yokosuka2, Hiroshi Hayashi’ We examined presence of estrogen and androgen receptors in the ventral premammillary nucleus (PMv) in adult and newborn rats. By immunohistochemistry, we detected androgen receptor (AR) but no estrogen receptor (ER) immunoreactivity (-ir) in this nucleus. In addition, there was clear sex difference (male > female) in the AR-ir in the PMv, that was reversed by orchidectomy or subcutaneous injections of a non-aromatizable androgen (5 alpha dihydrotestosterone). Furthermore, no aromatase was detected in the PMv. Thus, we postulate that distinct from the other brain regions such as the preoptic, the ventromedial hypothalmic and/or the medial amygdala nuclei, the PMv is a target of direct action of androgen. Since direct projections between the PMv and the limbic structures involved in male specific behavior have been reported, it is possible that the PMv of the perinatal male rat is masculized directly by androgen independent from the aromatization.

2410 Calcium dependence of excitatory postsynaptic currents of supraoptic neurons in hypothalamic slice preparation of mice

We found that immobilization-induced stress increases nitric oxide synthase (NOB) enzyme activity in the adrenal cortex (Tsuchiya T. et al., Psychoneuroendocrinology, 1996 in press : Kishimoto J. et al., Brain Res., 1996 in press). In the present study, we investigated whether this increase of mS enzyms activity induced by stress csn modify the stress-induced corticosterone response. The NOS enzyme activity in the adrenal cortex of rats 2h after the 2-h immbilization with pre-injection of saline was significantly higher (p<O.Ol) than that in the non-stressed control. Hcwever. pre-injection of a specific NOS inhibitor, L-NAME (lOOw/kg, B.C.), cwletely abolished the activity (95% inhibition, camarea with basal level). This dose of L-M maintained a significantly elevated plasma corticosterone level (9~0.05, cmared with basal level) even 2h after the Zh-stress, whereas, the plasma corticosterone level in rats pre-injected saline returned to the basal level 2h after the stress. These findings suggest that the stress-induced increase in hx) synthesis in the adrenal cortex can modify the stress-induced corticosterone response to facilitate the recovery of the elevated corticosterone secretion frao adrenal cortex ky stress to the resting basal level.

Frog Taste Cells After Denervation

The structure of the taste organ and the physiological properties of the taste cell of the bullfrog (Rana catesbeiana) were investigated after glossopharyngeal nerve transection.