Participation of opiatergic, GABAergic, and serotonergic systems in the expression of copulatory analgesia in male rats.

Copulation in the male rat provoked an abrupt and significant rise in the threshold to induce vocalization by electrical shock to the tail (copulatory analgesia, CA). The possible effect on CA of the intrathecal (IT) administration of receptor antagonists to neurotransmitters participating in nociception was ascertained in this study. CA was significantly reduced, though not abolished, by IT injections of either naloxone, picrotoxin, or methysergide, but not by strychnine or yohimbine.

Momentary analgesia produced by copulation in female rats.

To assess possible changes in nociception during copulation in estrous rats, electric shocks that were 20% suprathreshold for eliciting vocalization in response to tail shock (STS), were applied to the tail before the initiation of copulation and, thereafter, coincident with the onset of mounting bouts by the male (Experiment 1). Females vocalized significantly less during non-intromittive mounts (M; P < 0.001), intromissions (I; P < 0.

Copulatory analgesia in male rats ensues from arousal, motor activity, and genital stimulation: blockage by manipulation and restraint.

The effect of copulation on the vocalization threshold to tail shock (VTTS) was assessed in freely-moving, sexually experienced, Wistar male rats. Mean VTTS during the first copulation was 40% above the baseline values and slightly decreased during the first postejaculatory interval (PEI; 28% above baseline). VTTS mean values further increased during the second copulatory series (93% above baseline and 63% during the PEI).

Lordosis facilitation in estrogen primed rats by intrabrain injection of pregnanes.

Progesterone (P) and nine of its natural metabolites were bilaterally injected (5 micrograms in 0.5 microliter oil) into either the ventromedial hypothalamus (VMH) or the medial preoptic area (MPOA) of estrogen primed rats to assess their relative potencies for stimulating lordosis. P, 5 alpha-pregnanedione and 5 beta, 3 beta-pregnanolone elicited lordosis when injected at either VMH or MPOA.

Prevention of the convulsant and hyperalgesic action of strychnine by intrathecal glycine and related amino acids.

Intrathecal administration of 25 micrograms strychnine induced consistent sensory and motor behavioral events in rats. Sensory events included scratching and biting the lower half of the body, spontaneous vocalizations and skin hyperalgesia, evidenced by vocalization and reflex scratching in response to stimulation with a 5.5 g von Frey fiber.