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The effect of hypophysectomy and arginin-vassofressin on pain sensitivity in the rat
S416 SEXUAL RESPONSIVENESS AND ITS RELATIONSHIP 'TO VAGINAL STIMULATION-PRODUCED ANALGl$SIA IN THE RAT. J.?l. Rothfeld? L.R. Watkins and D.S. Gross? Departments of Anrmal rny siologY and Human Anatomy(DSG), Unlversitp of California. Davis CA 95616:
612 Poster Wednesday Adams l@
Increasing amounts of pressure applied LC the cervix produce a dosr response-like elevation of pain threshold in rats. This vaginal stimulation produced analgesia (VSPA) is facilitated in animals given estrogen(E) doses sufficient to induce high levels of sexual receptivity. Tt has been proposed that enhancement of VSPA may serve to decrease any noxious input associated with multiple intromissions by the male. In this study the antinociceptive effect of VSPA was compared in animals given E doses insufficient to increase receptivity with animals made receptive using suhthreshold E levels + progesterone(P) in an attempt to determine if enhancement of VSPA is due to the receptive state of the animal or the dose of E used. Tail flick latencies(TFL) and tail shock vocalization thresholds(TSVT) were measured in groups of E, E+P & oil treated rats during application of 0, 100 & 200gms of force on the cervix. Within oil, E 6 EP treated animals significant increases in TFL were observed at 100 & 200gm with respect to baseline (Ogm). Moreover at 1OOgm of force E treated animals displayed a significant increase in TFL over oil & E+P treated rats. In contrast, TSVT was increased at 100 d 200gm levels of probing in oil 6 E+P groups hut was not facilitated by E. In the present study, as in previous work, VSPA was potentiated by E; however this potentiation was not correlated with steroid induced receptivThat E was found to enhance TSL and not TSVT suggests that these reity. sponses are influenced by different control systems. Since it has been previously shown that naloxone antagonizes the effectiveness of VSPA in TFL but not TSVT tests, the differential responses to E observed here maybe a reflection of steroid interaction with endogenous opiate systems.
THE EFFECT OF HYPOPHYSECTOMY AND ARGININ-VASSOPRESSINON 613 Poster PAIN SENSITIVITY IN THE RAT. K.Sasaki, Y.Gotoh, K.Furukawa. Wednesday Adams 11 Hokkaido University School of Department of Anesthesiology, I ~~ Medicine., Sapporo, Japan. Aim of investigation: The relationship between hypophysectomy, arginin -vasopressin(AVP) and pain sensitivity was investigated in the rat. The effects of hypophysectomy and intra-ventricular administMethods: ration 05 AVP on pain sensitivity was tested in rats using the hot plate test.(56-1°C) The latency to exhibit a paw-lick response and subsequently Materials were 64 male a jump response was measured with a stopwatch. (1) Latency was measured 7 days after Wister rats weighing 170g to 18Og. Thereafter naloxone lmg/kg i.p. was injected to cerebra hypophysectomy. ventricular cannulated rats and latency was measured 30 min. later. (2) Latency was measured at 20 min and 30 min after injection of AVP O.Olug, O.lug, l.Oug and normal saline in 4~1 volume, i.c.v. AVP was administered i.c.v. 30 min after the injection of naloxone lmg/kg i.p. and latency was measured same as above. Latency of paw-lick and jump response of hypophysectomized + Results: ratzased significantly compared ty control rats. (15.6-1.6 vs. 9.71.5, paw-lick latency; 24.5-4.5 vs. 9.7-1.5, jump latency:p<0.05) After the injection of naloxone lmg/kg i.p., paw-lick and jump latency returned After the iqjection of AVP i.c.v+, latency increasto the control level. ed dqse-dependently. (salipe, 16.6~2.2;O.Olug AVP, 19.7-3.8; O.lug AVP, 54.8-21.7; l.Oug AVP, 72.1-5.3:X0.01 vs. saline) With pretreatment of naloxone lmg/kg i.p., prolonged latency due to AVP all returned to the control level. These results suggest that alternation of response to heat Conclusion: stimulation after hypophysectomy and administration of AVP i.c.v. is related with endogenous opiate-like substances.
612 Poster Wednesday Adams l@
Increasing amounts of pressure applied LC the cervix produce a dosr response-like elevation of pain threshold in rats. This vaginal stimulation produced analgesia (VSPA) is facilitated in animals given estrogen(E) doses sufficient to induce high levels of sexual receptivity. Tt has been proposed that enhancement of VSPA may serve to decrease any noxious input associated with multiple intromissions by the male. In this study the antinociceptive effect of VSPA was compared in animals given E doses insufficient to increase receptivity with animals made receptive using suhthreshold E levels + progesterone(P) in an attempt to determine if enhancement of VSPA is due to the receptive state of the animal or the dose of E used. Tail flick latencies(TFL) and tail shock vocalization thresholds(TSVT) were measured in groups of E, E+P & oil treated rats during application of 0, 100 & 200gms of force on the cervix. Within oil, E 6 EP treated animals significant increases in TFL were observed at 100 & 200gm with respect to baseline (Ogm). Moreover at 1OOgm of force E treated animals displayed a significant increase in TFL over oil & E+P treated rats. In contrast, TSVT was increased at 100 d 200gm levels of probing in oil 6 E+P groups hut was not facilitated by E. In the present study, as in previous work, VSPA was potentiated by E; however this potentiation was not correlated with steroid induced receptivThat E was found to enhance TSL and not TSVT suggests that these reity. sponses are influenced by different control systems. Since it has been previously shown that naloxone antagonizes the effectiveness of VSPA in TFL but not TSVT tests, the differential responses to E observed here maybe a reflection of steroid interaction with endogenous opiate systems.
THE EFFECT OF HYPOPHYSECTOMY AND ARGININ-VASSOPRESSINON 613 Poster PAIN SENSITIVITY IN THE RAT. K.Sasaki, Y.Gotoh, K.Furukawa. Wednesday Adams 11 Hokkaido University School of Department of Anesthesiology, I ~~ Medicine., Sapporo, Japan. Aim of investigation: The relationship between hypophysectomy, arginin -vasopressin(AVP) and pain sensitivity was investigated in the rat. The effects of hypophysectomy and intra-ventricular administMethods: ration 05 AVP on pain sensitivity was tested in rats using the hot plate test.(56-1°C) The latency to exhibit a paw-lick response and subsequently Materials were 64 male a jump response was measured with a stopwatch. (1) Latency was measured 7 days after Wister rats weighing 170g to 18Og. Thereafter naloxone lmg/kg i.p. was injected to cerebra hypophysectomy. ventricular cannulated rats and latency was measured 30 min. later. (2) Latency was measured at 20 min and 30 min after injection of AVP O.Olug, O.lug, l.Oug and normal saline in 4~1 volume, i.c.v. AVP was administered i.c.v. 30 min after the injection of naloxone lmg/kg i.p. and latency was measured same as above. Latency of paw-lick and jump response of hypophysectomized + Results: ratzased significantly compared ty control rats. (15.6-1.6 vs. 9.71.5, paw-lick latency; 24.5-4.5 vs. 9.7-1.5, jump latency:p<0.05) After the injection of naloxone lmg/kg i.p., paw-lick and jump latency returned After the iqjection of AVP i.c.v+, latency increasto the control level. ed dqse-dependently. (salipe, 16.6~2.2;O.Olug AVP, 19.7-3.8; O.lug AVP, 54.8-21.7; l.Oug AVP, 72.1-5.3:X0.01 vs. saline) With pretreatment of naloxone lmg/kg i.p., prolonged latency due to AVP all returned to the control level. These results suggest that alternation of response to heat Conclusion: stimulation after hypophysectomy and administration of AVP i.c.v. is related with endogenous opiate-like substances.