Table 1. Results of meta-analysis.
| MCH Signaling Function | Behavioral/Physiological/Biochemical Parameters | Sample Size | Number of Studies | r | 95% Confidence Interval | P value vs. 0 | |
| Lower Limit | Upper Limit | ||||||
| Anxiety- and Mood-Related Behavior | |||||||
| Elevated Plus Maze | 232 | 11 | 0.26 | 0.12 | 0.38 | <0.05 | |
| Elevated Plus Maze (Habituated Environment) | 84 | 4 | 0.26 | 0.03 | 0.46 | <0.05 | |
| Emergence Test | 42 | 2 | −0.33 | −0.02 | −0.58 | <0.05 | |
| Emergence Test (Habituated Environment) | 42 | 4 | −0.12 | 0.21 | −0.42 | N.S. | |
| Exploratory Behavior | 84 | 4 | 0.13 | −0.10 | 0.34 | N.S. | |
| Forced Swim test | 68 | 2 | 0.23 | −0.01 | 0.45 | N.S. | |
| Open Field Test | 330 | 9 | 0.26 | 0.15 | 0.36 | <0.05 | |
| Open Field Test (Habituated Environment) | 168 | 8 | 0.31 | 0.15 | 0.45 | <0.05 | |
| Response to Handling | 84 | 4 | 0.12 | −0.11 | 0.34 | N.S. | |
| Response to Novelty | 84 | 4 | 0.25 | 0.03 | 0.45 | <0.05 | |
| Response to Supine Restraint | 42 | 2 | 0.00 | −0.32 | 0.32 | N.S. | |
| Startle Response | 42 | 2 | 0.35 | 0.04 | 0.60 | <0.05 | |
| Stress−Induced Hyperthermia | 52 | 2 | 0.68 | 0.49 | 0.81 | <0.05 | |
| Body Weight and Energy Metabolism | |||||||
| Body Length | 54 | 3 | 0.17 | −0.12 | 0.44 | N.S. | |
| Body Temperature | 68 | 3 | −0.64 | −0.46 | −0.76 | <0.05 | |
| Body Temperature (Dark Phase) | 32 | 2 | −0.18 | 0.20 | −0.51 | N.S. | |
| Body Temperature (Light Phase) | 32 | 2 | −0.52 | −0.19 | −0.75 | <0.05 | |
| Body Weight | 192 | 11 | 0.25 | 0.10 | 0.39 | <0.05 | |
| Body Weight (High Fat Diet) | 90 | 5 | 0.49 | 0.30 | 0.64 | <0.05 | |
| Fat Mass | 143 | 11 | 0.67 | 0.55 | 0.76 | <0.05 | |
| Fat Mass (High Fat Diet) | 30 | 3 | 0.73 | 0.47 | 0.88 | <0.05 | |
| Food Intake | 129 | 7 | −0.26 | −0.08 | −0.43 | <0.05 | |
| Food Intake (High Fat Diet) | 116 | 7 | −0.21 | −0.02 | −0.40 | <0.05 | |
| Lean Mass | 82 | 5 | 0.19 | −0.04 | 0.41 | N.S. | |
| Lean Mass (High Fat Diet) | 16 | 2 | 0.17 | −0.42 | 0.66 | N.S. | |
| Liver Weight | 24 | 1 | 0.70 | 0.42 | 0.86 | <0.05 | |
| Oxygen Consumption | 24 | 3 | −0.96 | −0.90 | −0.99 | <0.05 | |
| Oxygen Consumption (High Fat Diet) | 15 | 2 | −0.98 | −0.94 | −1.00 | <0.05 | |
| Cardiovascular System | |||||||
| Heart Rate | 16 | 1 | −0.89 | −0.71 | −0.96 | <0.05 | |
| Heart Rate (Dark Phase) | 16 | 1 | −0.86 | −0.64 | −0.95 | <0.05 | |
| Heart Rate (Light Phase) | 16 | 1 | −0.68 | −0.28 | −0.88 | <0.05 | |
| Mean Arterial Pressure | 16 | 1 | −0.85 | −0.61 | −0.95 | <0.05 | |
| Mean Arterial Pressure (Dark Phase) | 16 | 1 | −0.24 | 0.29 | −0.66 | N.S. | |
| Mean Arterial Pressure (Light Phase) | 16 | 1 | −0.08 | 0.43 | −0.55 | N.S. | |
| Endocrinology and Lab Data | |||||||
| Blood Ethanol Kinetics | 72 | 4 | −0.06 | 0.19 | −0.30 | N.S. | |
| Corticosterone Level | 52 | 3 | −0.50 | −0.25 | −0.69 | <0.05 | |
| CRF Level in CE | 10 | 1 | 0.03 | −0.61 | 0.65 | N.S. | |
| CRF Level in PVN | 10 | 1 | 0.55 | −0.13 | 0.88 | N.S. | |
| Estrous Cycling | 20 | 1 | −0.18 | 0.28 | −0.58 | N.S. | |
| Free Fatty Acid Level | 24 | 1 | 0.05 | −0.36 | 0.44 | N.S. | |
| Ghrelin Level | 34 | 2 | 0.13 | −0.23 | 0.46 | N.S. | |
| Glucose Level | 124 | 7 | 0.18 | −0.01 | 0.36 | N.S. | |
| Glucose Level (High Fat Diet) | 64 | 6 | 0.08 | −0.21 | 0.35 | N.S. | |
| Insulin Level | 140 | 8 | 0.13 | −0.05 | 0.30 | N.S. | |
| Insulin Level (High Fat Diet) | 30 | 3 | 0.49 | 0.11 | 0.75 | <0.05 | |
| Leptin Level | 130 | 8 | 0.57 | 0.42 | 0.68 | <0.05 | |
| Leptin Level (High Fat Diet) | 30 | 3 | 0.65 | 0.33 | 0.83 | <0.05 | |
| Leptin Level (per gram Fat) | 17 | 2 | −0.17 | 0.39 | −0.65 | N.S. | |
| Leptin Level (per gram Fat) (High Fat Diet) | 36 | 4 | 0.51 | 0.16 | 0.74 | <0.05 | |
| Liver Triglyceride Level | 24 | 1 | 0.60 | 0.26 | 0.81 | <0.05 | |
| Liver Triglyceride Level (High Fat Diet) | 14 | 1 | 0.77 | 0.40 | 0.92 | <0.05 | |
| T4 Level | 66 | 3 | 0.54 | 0.33 | 0.70 | <0.05 | |
| Total Cholesterol Level | 24 | 1 | 1.00 | 1.00 | 1.00 | <0.05 | |
| Triglyceride Level | 72 | 3 | 0.20 | −0.05 | 0.42 | N.S. | |
| Learning and Memory | |||||||
| Spatial Learning Function | 42 | 2 | −0.21 | 0.12 | −0.49 | N.S. | |
| Locomotion | |||||||
| Locomotor Activity | 609 | 10 | −0.18 | −0.10 | −0.26 | <0.05 | |
| Locomotor Activity (High Fat Diet) | 15 | 2 | −0.93 | −0.77 | −0.98 | <0.05 | |
| Locomotor Activity (Dark Phase) | 56 | 5 | −0.59 | −0.36 | −0.75 | <0.05 | |
| Locomotor Activity (Dark Phase) (High Fat Diet) | 15 | 2 | −0.87 | −0.60 | −0.96 | <0.05 | |
| Locomotor Activity (Light Phase) | 32 | 2 | −0.30 | 0.07 | −0.60 | N.S. | |
| Reward System | |||||||
| Alcohol Preference | 30 | 2 | −0.59 | −0.26 | −0.79 | <0.05 | |
| Conditioned Place Preference | 14 | 1 | 0.66 | 0.20 | 0.88 | <0.05 | |
| Motor Activation by Psychostimulants | 38 | 1 | −0.44 | −0.13 | −0.66 | <0.05 | |
| Sensitization to Psychostimulants | 31 | 1 | −0.11 | 0.28 | −0.46 | N.S. | |
| Sucrose Preference | 15 | 1 | 0.39 | −0.15 | 0.75 | N.S. | |
| Sensorimotor Function | |||||||
| Motor Coordination | 210 | 10 | −0.11 | 0.03 | −0.25 | N.S. | |
| Olfaction | 13 | 1 | 0.60 | 0.08 | 0.87 | <0.05 | |
| Sleep-Wakefulness | |||||||
| Non-REM Sleep (24 h) | 68 | 3 | 0.54 | 0.33 | 0.70 | <0.05 | |
| Non-REM Sleep (Dark Phase) | 52 | 3 | 0.50 | 0.24 | 0.69 | <0.05 | |
| Non-REM Sleep (Light Phase) | 52 | 3 | 0.26 | −0.03 | 0.51 | N.S. | |
| REM Sleep (24 h) | 52 | 3 | −0.07 | 0.23 | −0.35 | N.S. | |
| REM Sleep (Dark Phase) | 52 | 3 | 0.01 | −0.28 | 0.30 | N.S. | |
| REM Sleep (Light phase) | 52 | 3 | −0.18 | 0.11 | −0.45 | N.S. | |
| Wakefulness (24 h) | 68 | 4 | −0.51 | −0.30 | −0.68 | <0.05 | |
| Wakefulness (Dark Phase) | 52 | 3 | −0.38 | −0.10 | −0.60 | <0.05 | |
| Wakefulness (Light Phase) | 52 | 3 | −0.22 | 0.08 | −0.48 | N.S. | |
| Social Behavior | |||||||
| Resident-Intruder Test | 16 | 1 | −0.70 | −0.32 | −0.89 | <0.05 | |
| Male Mating Behavior | 10 | 1 | −0.83 | −0.43 | −0.96 | <0.05 | |
| Social Interaction Test | 30 | 1 | −0.36 | 0.00 | −0.64 | <0.05 | |
| Aminergic and Peptidergic Signaling | |||||||
| Agouti-Related Protein Level in Hypothalamus | 12 | 1 | 0.19 | −0.43 | 0.69 | N.S. | |
| DA Level in NAc | 25 | 1 | 0.08 | −0.32 | 0.46 | N.S. | |
| DAT Level in CPu | 24 | 2 | −0.21 | 0.24 | −0.59 | N.S. | |
| DAT Level in GP | 10 | 1 | 0.00 | −0.63 | 0.63 | N.S. | |
| DAT Level in NAc | 34 | 3 | −0.21 | 0.18 | −0.54 | N.S. | |
| DAT Level in OT | 10 | 1 | 0.00 | −0.63 | 0.63 | N.S. | |
| DAT Level in SN | 10 | 1 | −0.16 | 0.53 | −0.72 | N.S. | |
| DAT Level in VTA | 10 | 1 | −0.29 | 0.42 | −0.78 | N.S. | |
| D1R Level in CPu | 24 | 2 | −0.03 | 0.41 | −0.45 | N.S. | |
| D1R Level in GP | 10 | 1 | 0.00 | −0.63 | 0.63 | N.S. | |
| D1R Level in NAc | 34 | 3 | 0.47 | 0.11 | 0.71 | <0.05 | |
| D1R Level in OT | 10 | 1 | 0.24 | −0.46 | 0.76 | N.S. | |
| D1R Level in SN | 10 | 1 | 0.24 | −0.46 | 0.76 | N.S. | |
| D1R Level in VTA | 10 | 1 | 0.63 | 0.00 | 0.90 | <0.05 | |
| D2R Level in CPu | 24 | 2 | 0.52 | 0.12 | 0.78 | <0.05 | |
| D2R Level in GP | 10 | 1 | 0.00 | −0.63 | 0.63 | N.S. | |
| D2R Level in NAc | 34 | 3 | 0.32 | −0.06 | 0.62 | N.S. | |
| D2R Level in OT | 10 | 1 | 0.63 | 0.00 | 0.90 | <0.05 | |
| D2R Level in SN | 10 | 1 | 0.24 | −0.46 | 0.76 | N.S. | |
| D2R Level in VTA | 10 | 1 | 0.24 | −0.46 | 0.76 | N.S. | |
| NE Level in NAc | 25 | 1 | 0.08 | −0.32 | 0.46 | N.S. | |
| NET Level in CPu | 10 | 1 | −0.14 | 0.53 | −0.71 | N.S. | |
| NET Level in GP | 10 | 1 | −0.78 | −0.30 | −0.95 | <0.05 | |
| NET Level in NAc | 20 | 2 | −0.64 | −0.24 | −0.86 | <0.05 | |
| NET Level in OT | 10 | 1 | −0.30 | 0.41 | −0.78 | N.S. | |
| NET Level in SN | 10 | 1 | −0.62 | 0.02 | −0.90 | N.S. | |
| NET Level in VTA | 10 | 1 | −0.51 | 0.18 | −0.86 | N.S. | |
| Neuropeptide Y Level in Hypothalamus | 12 | 1 | 0.19 | −0.43 | 0.69 | N.S. | |
| NR1 Subunit Level in HPC | 36 | 3 | 0.58 | 0.28 | 0.78 | <0.05 | |
| NR2A Subunit Level in HPC | 36 | 3 | 0.22 | −0.16 | 0.53 | N.S. | |
| NR2B Subunit Level in HPC | 36 | 3 | 0.22 | −0.16 | 0.53 | N.S. | |
| Orexin Level in Hypothalamus | 12 | 1 | −0.19 | 0.43 | −0.69 | N.S. | |
| Pro-Opiomelanocortin Level in Hypothalamus | 12 | 1 | 0.79 | 0.40 | 0.94 | <0.05 | |
| 5HT Level in NAc | 25 | 1 | 0.08 | −0.32 | 0.46 | N.S. | |
| 5HT Level in PFC | 18 | 1 | 0.83 | 0.60 | 0.94 | <0.05 | |
| 5HTT Level in CPu | 10 | 1 | 0.00 | −0.63 | 0.63 | N.S. | |
| 5HTT Level in GP | 10 | 1 | 0.32 | −0.39 | 0.79 | N.S. | |
| 5HTT Level in NAc | 20 | 2 | 0.25 | −0.26 | 0.65 | N.S. | |
| 5HTT Level in OT | 10 | 1 | 0.60 | −0.05 | 0.89 | N.S. | |
| 5HTT Level in SN | 10 | 1 | 0.43 | −0.27 | 0.83 | N.S. | |
| 5HTT Level in VTA | 10 | 1 | 0.00 | −0.63 | 0.63 | N.S. | |
| Others | |||||||
| Litter Size | 304 | 2 | 0.05 | −0.06 | 0.17 | N.S. | |
| Mean Pup Mass | 304 | 2 | 0.09 | −0.02 | 0.20 | N.S. | |
| Pup Mortality | 163 | 1 | −0.14 | 0.01 | −0.29 | N.S. | |
r = mean effect size, P value was calculated by Z test. CE, central amygdaloid nucleus; CPu, caudate-putamen; CRF, corticotropin-releasing factor; D1R, dopamine D1 receptor; D2R, dopamine D2 receptor; DA, dopamine; DAT, dopamine transporter; GP, globus pallidus; HPC, hippocampus; 5HTT, 5HT transporter; NAc, nucleus accumbens; NE, norepinephrine; NET, norepinephrine transporter; OT, olfactory tubercle; PFC, prefrontal cortex; PVN, paraventricular nucleus; SN, substantia nigra; VTA, ventral tegmental area.