Low copulatory activity in selectively bred Sardinian alcohol-nonpreferring (sNP) relative to alcohol-preferring (sP) rats

Figures & data

Table I. Ethogram of the behaviors scored by direct observation or calculated during the copulatory activity tests.

Parameters	Definitions
Latency mount	The time (s) from the introduction of the receptive female until the first mount was observed
Latency intromission	The time (s) from the introduction of the receptive female until the first intromission was observed
Latency ejaculation	The time (s) from the introduction of the receptive female until an ejaculation was observed
Frequency mount	The total number of observed mounts
Frequency intromission	The total number of observed intromissions
Frequency ejaculation ^a	The total number of observed ejaculations
Post-ejaculatory interval	The time (s) from ejaculation until the next observed intromission
Mounts + intromissions	The sum of observed mounts and intromissions
Mounts + intromissions/min	The sum of observed mounts and intromissions calculated per minute
Intromission ratio	The number of observed intromissions calculated in relation to the total number of observed mounts and intromissions
Time from first intromission to ejaculation	The elapsed time (s) from the first observed intromission until an observed ejaculation
Mounts + intromissions/ejaculation	The sum of mounts and intromissions required to reach ejaculation
Inter-intromission rate III	The latency (s) from the introduction of the receptive female until ejaculation divided by the total number of intromissions
Copulatory rate	The sum of mounts and intromissions divided by the elapsed time (s) from the first mount until an observed ejaculation

^aThe number of ejaculations was only scored in the first two tests, which lasted for 15 min each. Only one sP rat ejaculated twice, and this was in the first test. The third test lasted for a maximum of 30 min but was interrupted after scoring the post-ejaculatory interval.

Figure 2. Latency to first mount (A), intromission (B), and ejaculation (C) in the three copulatory behavior tests in male sP (n = 15) and Wistar (n = 10) rats. The latency to first mount (A) in the third test is also shown in the insert for a better illustration of the difference between sP and Wistar rats. Values represent individual data points with the median value marked as a line, and in the insert values represent median and quartile range. * p < 0.05 comparing sP and Wistar rats (Mann–Whitney U test); # p < 0.05, ## p < 0.01 compared to the first copulatory behavior test within the respective group (Wilcoxon signed rank test).

Figure 3. The number of mounts (A), intromissions (B), and sum of mounts and intromissions (C) in the three copulatory behavior tests in male sP (n = 15) and Wistar (n = 10) rats. Values represent individual data points with the median value marked as a line. # p < 0.05 compared to the first copulatory behavior test within the respective group (Wilcoxon signed rank test).

Figure 1. The percentage number of sNP (n = 15) and sP (n = 15) rats mounting (A), intromitting (B), and achieving ejaculation (C) over the three copulatory behavior tests. Due to the low number of sNP rats engaging in copulatory activity also in the third test, they were excluded from further detailed statistical analyses of copulatory behavior. Wistar (n = 10) rats were included as a reference strain. **p < 0.01, *** p < 0.001, **** p < 0.0001 compared to sP rats (chi-square test).

Table II. Copulatory behavior in sexually experienced sP and Wistar rats.

Parameters	sP				Wistar
	Median	Min	Max	Occ	Median	Min	Max	Occ
Latency mount	20.0	5.0	75.0	13/15	10.0	5.0	60.0	10/10	U = 37.5, p = 0.088
Frequency mount	16.0	6.0	61.0	13/15	23.5	2.0	73.0	10/10
Mounts/min	1.1	0.4	2.4	13/15	1.6	0.2	2.4	10/10
Latency intromission	90.0	25.0	1245.0	11/15	45.0	10.0	170.0	9/10
Frequency intromission	6.0	1.0	10.0	11/15	8.0	1.0	11.0	9/10
Intromissions/min	0.3	0.03	0.7	11/15	0.6	0.03	0.8	9/10
Mounts + intromissions	21.0	7.0	67.0	13/15	33.5	10.0	83.0	10/10
Mounts + intromissions/min	1.4	0.5	2.8	13/15	2.2	0.8	2.8	10/10	U= 35.0, p = 0.067
Intromission ratio	17.6	7.1	58.8	11/15	28.1	2.0	80.0	9/10
Latency ejaculation	395.0	130.0	780.0	8/15	435.0	280.0	750.0	5/10
Time from first intromission to ejaculation	280.0	40.0	725.0	8/15	425.0	225.0	735.0	5/10
Mounts + intromissions/ejaculation	18.5	7.0	28.0	8/15	22.0	10.0	35.0	5/10
Post-ejaculatory interval	312.5	230.0	520.0	8/15	245.0	190.0	340.0	5/10	U = 7.0, p = 0.065
Inter-intromission rate III ^a	98.2	54.5	130.0	8/15	48.3	43.8	74.4	5/10	U = 6.0, p < 0.050
Copulatory rate	0.06	0.03	0.1	8/15	0.05	0.03	0.06	5/10

Copulatory behavior in sP and Wistar rats during the third sexual behavior test, i.e. when the rats were sexually experienced from two previous tests. Values are expressed as median, min, and max. Occurrence (Occ), i.e. the number of animals displaying each behavior, is shown since behaviors that did not occur were considered missing values.

^ap < 0.05 comparing sP and Wistar rats, additional trends are shown (Mann–Whitney U test).