Examination of the role of adrenergic receptor stimulation in the sensitization of neuroinflammatory-based depressive-like behavior in isolated Guinea pig pups

Figures & data

Figure 1. A Representation of experimental timeline. (A) Guinea pig pups received no surgery or injections (UN), or surgery to implant telemetry devices and two injections of saline and saline (SS), low dose ephedrine and saline (LES), low dose ephedrine and cortisol (LEC), high dose ephedrine and saline (HES), or high dose ephedrine and cortisol (HEC) prior to isolation on the day after injection and at a comparable age for non-injected pups. (B) Guinea pig pups were treated with saline vehicle (VEH), or low dose propranolol (LP), or high dose propranolol (HP), prior to first isolation. They were then isolated again without injection 1 and 4 days later.

Schematic illustrating the timeline in which pups in each experiment received telemetry implants, injections, and isolation.

Table 1. Mean (standard error) for vocalizations, depressive-like behavior, core temperature (°C), and activity for Experiment 1.

	UN	SAL	LES	LEC	HES	HEC
Vocalizations	3157.1	4145.2	3366.7	3852.1	3229.7	3377.6
	(409.8)	(411.8)	(575.8)	(561.7)	(328.0)	(551.5)
Crouch	49.1	40.5	43.3	42.3	43.8	47.5
	(4.0)	(3.9)	(3.1)	(5.2)	(3.6)	(4.4)
Full Passive	19.9	14.3	12.5	13.0	14.5	11.4
	(3.2)	(4.0)	(3.5)	(2.6)	(3.2)	(3.2)
Core Temperature (^οC)	–	39.8	39.4	39.9	39.3	39.5
	–	(0.2)	(0.1)	(0.3)	(0.1)	(0.1)
Activity Counts	–	32.5	26.8	29.2	29.0	26.5
	(3.6)	(4.0)	(3.3)	(2.9)	(5.4)

Figure 2. Mean (A) core temperature and (B) activity across the 12, 15-min Time blocks for Experiment 1. Vertical lines indicated standard errors of the means. N’s = 10-12/Condition. The effect of Time Block was significant for core temperature, p < 0.001.

Line graphs showing that core temperature of all groups with telemetry probes in Experiment one rose and then fell during the three-hour test, while the activity of all groups declined. There were no differences among groups for either measure.

Figure 3. Mean number of vocalizations across isolations in Experiment 2. Guinea pig pups treated with high dose propranolol (HP) showed significantly reduced vocalizing during the first isolation. N’s = 13 or 14/Condition. Vertical lines indicate standard errors and dots illustrate individual values. * p < 0.05 vs VEH.

Histograms depicting the vocalizing of all three groups of Experiment two on all three test days. The high dose of propranolol significantly reduced vocalizing relative to the group injected with vehicle on the first day.

Figure 4. Mean number of 1-min intervals in which the depressive-like measures of (A) crouch and (B) full passive were Observed across isolations. Vertical lines indicate standard errors. N’s = 13 or 14/condition. The overall pattern of increasing behavior with repeated isolations was significant for both measures, p’s < 0.001.

Line graphs illustrating the level of crouching and full passive behavior of all three groups of Experiment 2 on all three test days. There was a significant sensitization of both measures across days, but no differences among groups.

Figure 5. Mean (A) core temperature and (B) activity counts across the 12, 15-min Time blocks for the three isolations of Experiment 2. Data points represent averages across drug conditions (N’s = 41/isolation). Vertical lines indicate standard errors of the means. The Isolation × Time Block interaction was significant for core temperature, p < 0.001.

Line graphs depicting changes in core temperature and activity across the three isolations. While temperature rose and then fell, and activity decreased, over the three hours of each isolation, overall temperature significantly increased from the first to third isolation.

Data availability statement

The data that support the findings of this study are available from the corresponding author, MBH, upon reasonable request.