Destructive Effects of Prenatal WIN 55212-2 Exposure on Central Nervous System of Neonatal Rats

Abstract

Background: Cannabinoid, particularly hashish and WIN 55212-2 (WIN), consumption during embryonic period may affect fetal growth, and the development of motor functioning, memory and cognitive functions. Therefore, the present study aimed to evaluate the effects of WIN 55212-2 during embryonic period on behavioral responses, as well as tissue and memory changes among neonatal rats.

Methods: WIN treated groups subcutaneously received daily doses of 0.5 or 1 mg/kg WIN suspended in 1% Tween-80-saline (1 ml/kg) from days 5 to 20 of pregnancy. The vehicle group received 1% Tween-80-saline from days 5 to 20 of pregnancy. Three, five and seven weeks after birth, the effects of maternal WIN consumption on infants' body weight, mortality, histological changes, motor functioning, and memory function were assessed.

Findings: Prenatal WIN consumption was associated with atrophy of cerebellum cortex in granular and Purkinje cells layers. WIN treatment of pregnant rats produced a significant decrease in the rearing frequency of the offspring, but significantly increased the grooming frequency at 22, 36 and 50 days of age. During the acquisition trials, approach latencies were not significantly different between all groups of rats (50 days old). When the trial was repeated 24 hours and seven days later (retention trial), the avoidance latencies of the WIN-exposed group were significantly shorter than those of the control and vehicle animals. The mortality percent was increased significantly and litter size was decreased significantly in WIN (1 mg/kg) treated rats compared to the control, vehicle and WIN (0.5 mg/kg) treatment groups.

Conclusion: These findings suggested that prenatal exposure to WIN probably induces long-term alterations in histological, motor functioning, and learning and memory parameters.

Keywords: Cerebellum; Hashish; Memory; Motor functioning; Prenatal exposure; WIN 55212-2.

Figure 1

Comparison of pregnancy duration and number of litter size for born rats in the studied groups; Results are illustrated as mean ± SEM (n = at least 8) ***: Significant difference with the control group (P < 0.001) †††, ††††: Significant differences with the vehicle group (P < 0.001 and P< 0.0001, respectively) ‡‡, ‡‡‡: Significant differences with the 0.5 mg/kg and 1 mg/kg WIN treated groups, respectively (P < 0.01 and P < 0.001, respectively)

Figure 2

The survival rate of born rats in the studied groups on day 1 and at the end of first to fifth postnatal weeks (The numbers were different: from 35 neonate rats in WIN 1 mg/kg group and maximum 61 rats in the control group)

Figure 3

Figure A illustrates the order of cerebellar cortical layers and high density of Purkinje cells in the control rats (molecular layer (M), Purkinje cell layer (P) and granular layer (G). Figure B illustrates different cerebellar cortex layers 30 days after birth of rats treated with WIN 55212-2 during embryonic period. In the treated group, Purkinje neuron cells are irregular and shattered and with lower density than the control group. The red arrowhead indicates the places damaged and the blue arrowhead indicates cell bodies from healthy Purkinje cells.

Figure 4

Comparison of the interval between rearing and grooming in the studied groups on 22, 36 and 50 postnatal days in figures A and B, respectively (n = 8) (Values are expressed as mean ± SEM.) *, **, ***, **** indicate significant differences with the control group (P < 0.05, P < 0.01, P < 0.001, and P < 0.0001, respectively) †, ††, †††, †††† indicate significant differences with the vehicle group (P < 0.05, P < 0.01, P < 0.001, and P < 0.0001, respectively)

Figure 5

Comparison of memory retrieval, the frequency of entrance into dark compartment and duration of staying in dark zone in the studied groups on days 1 and 7 after acquisition, and at the end of the seventh week after birth in Figures A, B, and C, respectively (n = 8) (Values are expressed as mean ± SEM.) *, **, ***, **** indicate significant differences with the control group (P < 0.05, P < 0.01, P < 0.001, and P < 0.0001, respectively) †, ††, ††† indicate significant differences with the vehicle group (P < 0.05, P < 0.01, and P < 0.001, respectively)