|Year : 2013 | Volume
| Issue : 1 | Page : 14-17
Evaluation of memory status following administration of depo-provera in female wistar rats
Oyekunle Akinloye Olanrewaju1, MA Alabi2, Okojie Akhabue Kenneth2
1 Physiology Department, Ladoke Akintola University of Technology, Ogbomoso, Oyo State, Nigeria
2 University of Nigeria, Enugu Campus, Enugu State, Nigeria
|Date of Web Publication||30-Dec-2013|
Okojie Akhabue Kenneth
Physiology Department, University of Nigeria, Enugu Campus, Enugu State
Source of Support: None, Conflict of Interest: None
Background: Medroxyprogesterone acetate (MPA) is the most commonly used progestin component of hormone therapy (HT). In vitro, MPA negatively impacts markers of neuronal health and exacerbates experimentally induced neurotoxicity. There is in vitro evidence that these factors are driven by GABAergic and neurotrophic systems. Whether these effects translate to a negative impact on brain function has not been tested in vivo, clinically or preclinically. Aim: The goal of the present study was to determine whether MPA exerts detrimental effects on cognitive function in actively reproducing rats using Y-maze apparatus. Materials and Methods: Twenty-four female rats were randomly selected into three groups. Control group, Low dose (100 mg/1 ml MPA) group, and High dose (200 mg/1 ml MPA) group, respectively. Dose was delivered by intramuscular injection for the period of 3 weeks. Result: Intramuscular administration of MPA resulted in a dose-dependent decrease in memory and locomotion activities of the female wistar rats (P < 0.05). Discussion: These findings suggest that MPA, the most commonly used progestin in HT, is detrimental to learning and two types of memory, and possibly modulates the GABAergic system in cognitive brain regions, in actively reproducing rats. These findings, combined with in vitro evidence that MPA is detrimental to neuronal health, indicates that MPA has negative effects for brain health and function. Conclusion: Therefore, MPA despite being effective in modulating hormonal interaction to prevent conception in actively reproducing females, learning and memory depression could be one of its adverse effects.
Keywords: Depo-Provera (medroxyprogesterone), memory, Y-maze
|How to cite this article:|
Olanrewaju OA, Alabi M A, Kenneth OA. Evaluation of memory status following administration of depo-provera in female wistar rats. Niger J Exp Clin Biosci 2013;1:14-7
|How to cite this URL:|
Olanrewaju OA, Alabi M A, Kenneth OA. Evaluation of memory status following administration of depo-provera in female wistar rats. Niger J Exp Clin Biosci [serial online] 2013 [cited 2020 Sep 28];1:14-7. Available from: http://www.njecbonline.org/text.asp?2013/1/1/14/123957
| Introduction|| |
Depo-Provera (medroxyprogesterone acetate; (MPA) 150 mg intramuscular injection every 12 weeks is one of the most common methods of contraception used by female population in the advanced and advancing countries.  The endometrial thickness of the uterus is affected by Depo-Provera amidst other effects of its usage, to such an extent that it creates an unfavorable environment for implantation of a fertilized ovum, should ovulation occur.  It is therefore regarded as one of the most effective contraceptive methods available. During the postpartum period it has some influence on lactation yet allows the mother to continue with breast feeding. This specific contraceptive method has both benefits as well as disadvantages. Currently some of the disadvantages of Depo-Provera are actually utilized from a therapeutic prospective. Therefore, patients regularly present to the general practitioner with signs and symptoms related to side effects of Depo-Provera 150 mg injection. Some of its side effects, for example, amenorrhea, may be a cause of concern to some patients, while in others, for example, women who suffer from endometriosis, it may have a therapeutic effect.  Other side-effects of Depo-Provera include acne, fluid retention, changes in weight and libido, depression, breast tenderness, and breakthrough bleeding, which represent the most common reasons for seeking medical attention. 
Memory, one of the most astonishing capabilities of the brain, is the consequence of learning. Whereas learning is the acquisition of new knowledge, memory is the persistence of that learning, with the ability to access it at a later time. Two types of memory, short-term and long-term, have been recognized for many years, and researchers are now beginning to realize that they differ in characteristics other than duration.  Clinical studies in menopausal and postmenopausal women have demonstrated positive effects of estrogen-containing hormone therapy (HT) on memory and cognition. , However, the cognitive effectiveness of HT has been of much debate, due to the unexpected findings of the large, placebo-controlled, randomized Women's Health Initiative Memory Study (WHIMS) conducted by the National Institute of Health. Menopausal women taking Premarin alone did not differ significantly from those taking placebo for dementia diagnoses.  In contrast, twice as many women receiving Prempro were diagnosed with dementia as compared with the placebo group, a significant effect. 
MPA may be a key factor in Prempro that caused cognitive impairments, although many variables could be involved in this negative outcome.  There has been no study directly testing the hypothesis that MPA is detrimental to cognition in women or an animal model, however, there is indirect evidence that MPA is detrimental to the brain and its function.  Indeed, MPA exacerbated neuronal death by glutamate-induced excitotoxicity,  reduced estrogen-mediated neural protection against excitotoxicity,  and completely blocked the glutamate-stimulated calcium increase produced by 17 β-estradiol, a positive mechanism by which estrogens may modulate cognitive functioning. 
Therefore, the aim of this study was to assess memory status using Y-maze following administration of MPA in female wistar rats.
| Materials and Methods|| |
Twenty-four female reproducing Wistar rats weighing 140-180 g were used. All animals were kept under standard vivarium conditions (preclinical animal house of Ladoke Akintola University of Technology) at 23 ± 2°C and 12 h light/dark cycle. The animals were fed with standard rat pellet food, and normal saline for drinking was provided ad libitum. They were acclimatized in the laboratory for at least 1 week before the experimental session. All experimental procedures were carried out following the experimental guidelines of the Institutional Animal Ethics Committee (IAEC).
The animals were divided equally into three groups. Group I served as control and received 10 ml normal saline/kg body, group II received 100 mg/1 ml MPA while group III received 200 mg/1 ml Depo-Provera. Depo-Provera was administered once a week for 3 weeks intramuscularly. Animals were allowed 1 week rest to allow for uniformity of the drug in circulation before the test procedure. Depo-Provera was procured from Pfizer. The ampoule was shaken vigorously for about 10 seconds to allow for uniform concentration. A total of 20% and 50% of the recommended dosage of 150 mg/ml were prepared for intramuscular injection and given in 100 mg/ml and 200 mg/ml to the two test groups, respectively.
Y-maze apparatus is composed of three equally spaced arms (120°; 41 cm long × 15 cm high). The floor of each arm consists of wood (5 cm wide). An arm entry is defined as the body of a rat except for its tail completely entering into an arm compartment.  An alternation is defined as an entry into all three arms on consecutive choices.  Y-Maze is a gross test for spatial memory. It tests to see if the mouse remembers the arm it has just explored and will therefore enter one of the other arms of the maze. The experiment is carried out by introducing each rat at the center of the apparatus. As the rat moves, the spontaneous alternation (memory) and locomotor activity is recorded for 6 minutes without reinforcing. The apparatus is cleaned with methylated spirit and allowed to dry between sessions.
Differences between the three groups were analyzed using one-way analysis of variance (ANOVA). If significant, a posthoc test was carried out for multiple comparisons between the groups. A probability value of P < 0.05 was considered significant.
| Results|| |
As shown in [Figure 1], Depo-Provera significantly (P < 0.05) reduced memory in female wistar rats after a term of 3 weeks intramuscular administration (once in every week for 3 weeks). This reduction in memory was observed in dose-dependent manner when compared with control group.
As shown in [Figure 2], Depo-Provera also significantly (P < 0.05) reduced locomotor activities in female wistar rats after a term of 3 weeks intramuscular administration (once in every week for 3 weeks). This reduction in locomotor was observed in dose-dependent manner when compared with control group.
| Discussion|| |
The current study test the synthetic progestin MPA, the most commonly utilized progestin component of HT,  for learning and memory in the female wistar rats. We observed that MPA impaired memory and locomotive activities. Specifically, MPA impaired the ability to handle an increasing working memory on the Y-maze test over a period of 6 minutes. MPA effects were dose dependent, with the highest dose showing more detrimental effects. Bimonte-Nelson showed that natural progesterone also impaired memory, which is in agreement with this finding. 
Progesterone's detrimental effects on cognition have also been seen in women. Data suggest that in pregnant women the "maternal amnesia" phenomenon is due to high circulating progesterone levels.  Moreover, as demonstrated by the WHIMS collective findings, there is evidence that the combination of estrogen and MPA has a greater negative impact on cognition,  than estrogen alone. 
One of the possible mechanisms through which MPA brings about cognitive impairment could be alteration in glutamic acid decarboxylase (GAD) levels. Current findings demonstrate that both natural progesterone and the synthetic MPA either significantly or marginally alter GAD levels in the hippocampus and entorhinal cortex. GAD is the synthesizing enzyme and rate limiting step of GABA synthesis. There is a strong positive correlation between GAD mRNA levels and GABA neuronal activity,  making GAD a good neuronal marker for GABAergic function. 
The ring-A reduced metabolites of progesterone have a very high affinity for the GABA A receptor.  Progesterone-induced memory impairments are related to GABAergic system alterations. Providing support for this, the hippocampus and related brain regions affected by aging and mediating memory processing are largely controlled by the GABAergic system,  and experimental manipulation of progesterone alters the GABAergic system. For example, progesterone administration decreases GAD, the synthesizing enzyme and rate limiting step of GABA production, activity in the rodent dorsal hippocampus.  Progesterone metabolite, allopregnanolone, impairs reference memory in young male rats  and can impair reference memory and working memory in female rats. 
Additionally, MPA pretreatment exacerbates neuronal death induced by glutamate excitotoxicity in cultured hippocampal neurons.  Therefore, while the specific mechanism(s) by which progestins alter GAD levels in the hippocampus and entorhinal cortex is unknown, several neuronal actions of these compounds are documented this could independently or interactively contribute to altered GAD levels. Further studies manipulating the GABAergic system after progestin administration will be integral to this mechanistic understanding.
| Conclusion|| |
The current study showed that not only natural progesterone, but also the synthetic progestin MPA, the most common progestin included in HT, impairs memory and possibly bring about this effect through the alteration of the GABAergic system in cognitive brain regions in the menopausal rat. The current study has significant implications for the components of HT that might impact cognitive functioning, and suggest that MPA is detrimental within this region.
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[Figure 1], [Figure 2]