Kristal, M.B.  (1973). Effects of lateral hypothalamic lesions on placentophagia in virgin, primiparous, and multiparous rats. Journal of Comparative and Physiological Psychology, 84:53-62.

Kristal, M.; Wampler, R.S. (1973). Food and water intake prior to parturition in the rat. Physiological Psychology, 1:297-300.  

Kristal, M.B.; Williams, C.L. (1973).  The effects of strain, reproductive condition and strain of placenta donor, on placentophagia in nonpregnant mice.  Physiological Psychology, 1:354-356. 

Kristal, M.B.; Graber, G.C. (1976).  Placentophagia in nonpregnant rats:  Influence of estrous cycle stage and birthplace. Physiology & Behavior, 17:599-605. 

Engwall, D.B.; Kristal, M.B. (1977).  Placentophagia in rats is modifiable by taste aversion conditioning. Physiology & Behavior, 18:495-502. 

Graber, G.C.; Kristal, M.B. (1977). Uterine distention facilitates the onset of maternal behavior in pseudopregnant but not in cycling rats. Physiology & Behavior, 19:133-137. 

Kristal, M.B.; Axelrod, S.; Noonan, M. (1978). Learning in escape/avoidance tasks in female rats does not vary with reproductive condition. Physiology & Behavior, 21:251-156.

Noonan, M.; Kristal, M.B. (1978).  Nonparturitional exposure to donor placenta and placentophagia after lateral hypothalamic lesions in rats.  Bulletin of the Psychonomic Society, 12:140-142.

Kristal, M.B.; Noonan, M. (1979). Perinatal maternal behavior and neonatal behavior in the captive reticulated giraffe. South African Journal of Zoology, 14:103-107.

Kristal, M.B.; Noonan, M. (1979).  A note on sleep in captive giraffes (Giraffa camelopardalis reticulata). South African Journal of Zoology (formerly Zoologica Africana), 14:108.

Noonan, M.; Kristal, M.B. (1979). The effects of medial preoptic lesions on placentophagia and on the onset of maternal behavior in the rat. Physiology & Behavior, 22:197-1202. 

Kristal, M.B.; Steuer, M.A.; Nishita, J.K.; Peters, L.C. (1980). Neophobia and water intake after repeated pairings of novel flavors with toxicosis. Physiology & Behavior, 24:979-982. 

Kristal, M.B. (1980). Placentophagia: A biobehavioral enigma (or De gustibus non disputandum est). Neuroscience and Biobehavioral Reviews, 4:141-150. 

Kristal, M.B.; Whitney, J.F.; Peters, L.C. (1981).  Placenta on pups' skin accelerates onset of maternal behaviour in nonpregnant rats. Animal Behaviour, 29:81-85. 

Kristal, M.B.; Peters, L.C.; Franz, J.R.; Whitney, J.F.; Nishita, J.K.; Steuer, M.A. (1981).  Effect of pregnancy and stress on onset of placentophagia in Long-Evans rats.  Physiology & Behavior, 27:591-595. 

Kristal, M.B.; Nishita, J.K. (1981).  Observing birth and placentophagia affects placentophagia but not maternal behavior of virgin rats.  Animal Learning and Behavior, 9:545-550. 

Peters, L.C.; Kristal, M.B. (1983). The suppression of infanticide in mother rats. Journal of Comparative Psychology, 97:167-177. 

Kristal, M.B.; Thompson, A.C.; Grishkat, H.L. (1985). Placenta ingestion enhances opiate analgesia in rats. Physiology & Behavior, 35:481-486. 

Franz, J.R.; Leo, R.J.; Steuer, M.A.; Kristal, M.B. (1986). Effects of hypothalamic knife cuts and experience on maternal behavior in the rat. Physiology & Behavior, 38:629-640. 

Kristal, M.B.; Thompson, A.C.; Heller, S.B.; Komisaruk, B.R. (1986).  Placenta ingestion enhances analgesia produced by vaginal/cervical stimulation in rats.  Physiology & Behavior, 36:1017-20. 

Kristal, M.B.; Thompson, A.C.; Abbott, P. (1986).  Ingestion of amniotic fluid enhances opiate analgesia in rats. Physiology & Behavior, 38:809-815. 

Steuer, M.A.; Thompson, A.C.; Doerr, J.C.; Youakim, M.; Kristal, M.B. (1987). Induction of maternal behavior in rats: Effects of pseudopregnancy termination and placenta-smeared pups. Behavioral Neuroscience, 101:219-227. 

Peters, L.C.; Kristal, M.B.; Komisaruk, B.R. (1987). Sensory innervation of the external and internal genitalia of the female rat. Brain Research, 408:199-204. 

Kristal, M.B.; Abbott, P.; Thompson, A.C. (1988). Dose-dependent enhancement of morphine-induced analgesia by ingestion of amniotic fluid and placenta. Pharmacology, Biochemistry & Behavior, 31:351-356. 

Doerr, J.C.; Kristal, M.B. (1989).  Enhancement of opioid-mediated analgesia by ingestion of amniotic fluid: Onset latency and duration.  Physiology & Behavior, 46:913-915. 

Kristal, M.B.; Thompson, A.C.; Abbott, P.; DiPirro, J.M.; Ferguson, E.J.; Doerr, J.C. (1990). Amniotic fluid ingestion by parturient rats enhances pregnancy-mediated analgesia. Life Sciences, 46:693-698. 

Kristal, M.B.; Tarapacki, J.A.; Barton, D. (1990).  Amniotic fluid ingestion enhances opioid-mediated but not nonopioid-mediated analgesia.  Physiology & Behavior, 47:79-81. 

Kristal, M.B. (1991) Enhancement of opioid-mediated analgesia: A solution to the enigma of placentophagia. Neuroscience and Biobehavioral Reviews, 15:425-435. 

Thompson, A.C.; Abbott, P.; Doerr, J.C.; Ferguson, E.J.; Kristal, M.B. (1991) Amniotic-fluid ingestion before vaginal/cervical stimulation produces a dose-dependent enhancement of analgesia and blocks pseudopregnancy. Physiology & Behavior , 50, 11-15. 

Peters, L.C.; Sist, T.C.; Kristal, M.B. (1991). Maintenance and decline of infanticide-suppression in maternal rats. Physiology & Behavior, 50:451-456. 

DiPirro, J.M.; Thompson, A.C.; Kristal, M.B. (1991)  Amniotic-fluid ingestion enhances the central analgesic effect of morphine. Brain Research Bulletin, 26:851-855. 

Doerr, J.C.; Kristal, M.B. (1991)  Amniotic-fluid ingestion enhances morphine analgesia during morphine tolerance and withdrawal in rats. Physiology & Behavior, 50:633-635. 

Abbott, P.; Thompson, A.C.; Ferguson, E.J.; Tarapacki, J.A.; Kostyniak, P.J.; Syracuse, J.A.; Cartonia, D.M.; Kristal, M.B. (1991).  Placental opioid-enhancing factor (POEF): Generalizability of effects. Physiology & Behavior, 50:933-940. 

Tarapacki, J.A.; Thompson, A.C.; Kristal, M.B. (1992).  Gastric vagotomy blocks opioid-analgesia enhancement produced by placenta ingestion. Physiology & Behavior, 52:179-182. 

Tarapacki, J.A.; Piech, M.; Kristal, M.B. (1995). Ingestion of amniotic fluid by postpartum rats enhances morphine analgesia without liability to maternal behavior. Physiology & Behavior, 57:209-212. 

Robinson, T.M.; Abbott, P.; Kristal, M.B. (1995)  Blockade of digestion by famotidine pretreatment does not interfere with the opioid-enhancing effect of ingested amniotic fluid.  Physiology & Behavior, 57:261-263. 

Thompson, A.C.; Kristal, M.B. (1996). Opioid stimulation in the ventral tegmental area facilitates the onset of maternal behavior in rats. Brain Research, 743:184-201. 

Horowitz, J.M.; DiPirro, J.M.; Kristal, M.B.; Torres, G. (1997).  Dopaminergic, glutamatergic but not opioidergic mechanisms mediate induction of FOS-like protein by cocaethylene.  Brain Research Bulletin, 42:393-398.

Horowitz, J.M.; Kristal, M.B.; Torres, G. (1997).  Differential behavioral responses to cocaethylene of Long-Evans and Sprague-Dawley rats: Role of serotonin. Synapse, 26:11-21.

Robinson-Vanderwerf, T.M.; DiPirro, J.M.; Caggiula, A.R.; Kristal, M.B. (1997).  The analgesia-enhancing component of ingested amniotic fluid does not affect nicotine-induced antinociception in naltrexone-treated rats. Pharmacology Biochemistry & Behavior, 58:147-151.

Baumann, M.H.; Horowitz, J.M.; Kristal, M.B.; Torres, G. (1998). Effects of cocaethylene on dopamine and serotonin synthesis in Long-Evans and Sprague-Dawley brains. Brain Research, 804:316-319.

Kristal, M.B. (1998): Participation of Placental Opioid-Enhancing Factor in opioid-modulated events at parturition. In invited symposium: "Genital Sensation: CNS Target and Functions in Females." On-line Proceedings of the 5th Internet World Congress on Biomedical Sciences '98 at McMaster University, Canada.

Corpening, J.W.; Doerr, J.C.;  Kristal, M.B. (2000).  Ingested bovine amniotic fluid enhances morphine antinociception in rats. Physiology & Behavior, 70:15-18. 

INVITED ARTICLE: Kristal, M.B. (2000). "Anarchy Rules." The Buffalo News, Sunday, June 18, 2000.

Martin, L.B.E.; Thompson, A.C.; Martin, T.; Kristal, M.B. (2001). Analgesic efficacy of orally administered buprenorphine in rats. Comparative Medicine, 51:43-48.

Dodge, J.C.; Kristal, M.B.; Badura, L.L. (2002). Male-induced estrus synchronization in the female Siberian hamster (Phodopus sungorus sungorus). Physiology & Behavior, 77:227-231.

DiPirro, J.M.; Kristal, M.B. (2004). Placenta ingestion by rats enhances delta- and kappa- opioid antinociception, but suppresses mu-opioid antinociception. Brain Research, 1014:22-33.

Corpening, J.W.; Doerr, J.C.; Kristal, M.B. (2004). Ingested placenta blocks the effect of morphine on gut transit in Long-Evans rats. Brain Research, 1016:217-221.

Thompson, A.C.; Kristal, M.B.; Sallaj, A.; Acheson, A.; Martin, L.B.E.; Martin, T. (2004). Analgesic efficacy of oral buprenorphine in rats: Methodological considerations. Comparative Medicine, 54:293-300.

Kristal, Mark B.  (2005). Advice for Graduate Students: The 10 Suggestions for a Basic-Research Career. IBNS Newsletter, 9(2).

INVITED ARTICLE: Kristal, M.B. (2006). "Darwin Under Attack." The Buffalo News, Sunday, January 29, 2006.

Thompson, A.C.; DiPirro, J.M.; Sylvester, A.R.; Martin, L.B.E.; Kristal, M.B. (2006). Lack of analgesic efficacy in females of the commonly recommended dose of oral buprenorphine. Journal of the American Association for Laboratory Animal Science, 45:13-16.

INVITED ARTICLE: Kristal, M.B. (2009). The biopsychology of maternal behavior in nonhuman mammals. ILAR Journal (Institute for Laboratory Animal Research - NAS/NRC), 50:51-63.

Neumann, A.; Hoey, R.F.; Daigler, L.B.; Thompson, A.C.; Kristal, M.B. (2009).  Ingestion of amniotic fluid enhances the facilitative effect of VTA morphine on the onset of maternal behavior in virgin rats. Brain Research, 1261:29-36.

Curtin, L.I.;  Grakowsky, J.A.; Suarez, M.; Thompson, A.C.; DiPirro, J.M.; Martin, L.B.E.; Kristal, M.B. (2009). Evaluation of buprenorphine in a post-operative pain model in  rats. Comparative Medicine, 59:60-71.

Hoey, R.F.; Hurley, S.W.; Daniels, D.; Kristal, M.B. (2011). Effect of amniotic-fluid ingestion on vaginal/cervical-stimulation-induced Fos expression in female rats during estrus. Brain Research, 1376:51-59. 

INVITED ARTICLE: Kristal, M.B.; DiPirro, J.M.; Thompson, A.C. (2012). Placentophagia in humans and nonhuman mammals: Causes and consequences. Ecology of Food and Nutrition, 51: 177-197.  

INVITED ARTICLE: Kristal M.B. (2012). "Placenta: To Eat or Not to Eat?" The Huffington Post

Thompson, A.C.; Feeney, C.; Kristal M.B. (2018). Amniotic-fluid ingestion enhances central δ-opioid-induced hypoalgesia in rats in the cold-water tail-flick assay in a repeated-measures design.  Brain Research, 1697: 53-58.

Kristal, M.B.; DiPirro, J.M.; Thompson, A.C.; Wood, T.D. (2023). Placentophagia and the Tao of POEF. Neuroscience & Biobehavioral Reviews, 145: 104992.

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