The Partial M1 Muscarinic Cholinergic Receptor Agonist, CDD-0102A, Differentially Modulates Glutamate Efflux in Striatal Subregions during Stereotyped Motor Behavior in the BTBR Mouse Model of Autism

Abstract

The BTBR T⁺ Itpr3^tf/J (BTBR) mouse displays elevated repetitive motor behaviors. Treatment with the partial M₁ muscarinic receptor agonist, CDD-0102A, attenuates stereotyped motor behaviors in BTBR mice. The present experiment investigated whether CDD-0102A modifies changes in striatal glutamate concentrations during stereotyped motor behavior in BTBR and B6 mice. Using glutamate biosensors, change in striatal glutamate efflux was measured during bouts of digging and grooming behavior with a 1 s time resolution. Mice displayed both decreases and increases in glutamate efflux during such behaviors. Magnitude of changes in glutamate efflux (decreases and increases) from dorsomedial and dorsolateral striatum were significantly greater in BTBR mice compared to those of B6 mice. In BTBR mice, CDD-0102A (1.2 mg/kg) administered 30 min prior to testing significantly reduced the magnitude change in glutamate decreases and increases from the dorsolateral striatum and decreased grooming behavior. Conversely, CDD-0102A treatment in B6 mice potentiated glutamate decreases and increases in the dorsolateral striatum and elevated grooming behavior. The findings suggest that activation of M₁ muscarinic receptors modifies glutamate transmission in the dorsolateral striatum and self-grooming behavior.

Keywords: Striatum; acetylcholine; autism; biosensor; glutamate; muscarinic.

Figure 1

Biosensor electrode placements in the dorsal striatum of B6 and BTBR mice included in the neurochemical and behavioral analyses. Mouse brain section reproduced with permission from Paxinos G.; Franklin K. B.. Paxinos and Franklin’s The Mouse Brain in Stereotaxic Coordinates, compact 5th ed.; Elsevier Academic Press: San Diego, CA, 2019.(48) The black circles (●) represent biosensor placements for mice receiving saline treatment. The open circles (○) represent biosensor placements for mice receiving CDD-0102A treatment (1.2 mg/kg).

Figure 2

Timeline of experimental design illustrating the order of the procedures for biosensor recordings combined with behavioral testing. The biosensor was first calibrated and demonstrated to be sensitive and selective to varying concentrations of glutamate. Subsequently, a biosensor was inserted into the dorsal striatum and allowed to equilibrate in the brain for 3 h. After equilibration, a mouse received an intraperitoneal injection of saline or CDD-0102A (1.2 mg/kg). Thirty minutes after injection the nesting material was removed from the home cage and bouts of digging and grooming were measured along with glutamate efflux for 20 min. Finally, the biosensor was removed from the brain and a postcalibration of the biosensor was conducted.

Figure 3

Glutamate changes in the dorsolateral striatum during stereotyped motor behavior. (A) Saline-treated B6 and BTBR mice exhibited both decreases and increases in glutamate during stereotyped motor behavior with the magnitude change significantly greater in BTBR mice compared to that of B6 mice. CDD-0102A (1.2 mg/kg) injected intraperitoneally significantly reduced the decreased and increased changes in glutamate for BTBR mice, while the drug significantly increased the magnitude change in B6 mice. **P < 0.001 vs B6-Saline, ^#P < 0.05 vs BTBR-Saline. CDD = CDD-0102A 1.2 mg/kg. (B) The mean decrease in glutamate concentration across the 3 s preceding a behavioral bout (baseline) and first 3 s of a behavioral bout B6 and BTBR mice. BTBR controls had significantly greater decreases in glutamate efflux vs B6 controls. CDD-0102A treatment reduced the magnitude decrease at second 3 in BTBR mice and significantly potentiated decrease in the first 2 s in B6 mice. (C) The mean increase in glutamate concentration across the 3 s preceding a behavioral bout (baseline) and the first 3 s of a behavioral bout in B6 and BTBR mice. BTBR controls had significantly greater increases in glutamate efflux vs B6 controls. CDD-0102A treatment in BTBR mice significantly attenuated the glutamate increases in the first 3 s of a bout. (D) Mean decrease in glutamate during stereotyped motor behavior for short duration and long duration bouts. Short and long bouts were defined as being less than or equal to/greater than the median for that condition, respectively. Changes in glutamate concentration did not differ between short and long bouts within a treatment for both strains. (E) Mean increase in glutamate during stereotyped motor behavior for short duration and long duration bouts. Changes in glutamate concentration did not differ between short and long bouts within a treatment for both strains.

Figure 4

Glutamate changes in the dorsomedial striatum during stereotyped motor behavior. (A) Saline-treated B6 and BTBR mice exhibited both decreases and increases in glutamate during stereotyped motor behavior with the magnitude change significantly greater in BTBR mice compared to that of B6 mice. CDD-0102A (1.2 mg/kg) injected intraperitoneally did not affect glutamate changes in either strain. **P < 0.001 vs B6-Saline. CDD = CDD-0102A 1.2 mg/kg. (B) The mean decrease in glutamate concentration across the 3 s preceding a behavioral bout (baseline) and the first 3 s of a behavioral bout B6 and BTBR mice. BTBR controls had significantly greater decreases in glutamate efflux vs B6 controls. (C) The mean increase in glutamate concentration across the 3 s preceding a behavioral bout (baseline) and the first 3 s of a behavioral bout in B6 and BTBR mice. BTBR controls had significantly greater increases in glutamate efflux vs B6 controls. (D) Mean decrease in glutamate during stereotyped motor behavior for short duration and long duration bouts. Short and long bouts were defined as being less than or equal to/greater than the median for that condition, respectively. Changes in glutamate concentration did not differ between short and long bouts within a treatment for both strains. (E) Mean increase in glutamate during stereotyped motor behavior for short duration and long duration bouts. Changes in glutamate concentration did not differ between short and long bouts within a treatment for both strains.

Figure 5

CDD-0102A effects on stereotyped motor behavior. (A) CDD-0102A (1.2 mg/kg) significantly reduced grooming behavior in BTBR mice while significantly increasing grooming behavior in B6 mice. **P < 0.001 vs B6-Saline, ^##P < 0.01 vs BTBR-Saline. (B) CDD-0102A (1.2 mg/kg) effect on mean grooming bout duration. BTBR mice had higher mean grooming bout durations than B6 mice. CDD-0102A treatment did not affect mean bout duration. (C) CDD-0102A effect on total number of grooming bouts. Drug treatment significantly increased the total number of grooming bouts in B6 mice and significantly decreased the total number of grooming bouts in BTBR mice. **P < 0.001 vs B6-Saline, ^#P < 0.05 vs BTBR-Saline.