Effects of exercise on male copulatory behavior after β-adrenoreceptor blockade

Chronic activity-wheel running enhances male copulation and is associated with brain noradrenergic adaptations that may be modulated by the neuropeptide galanin (GAL). When injected into the medial pre-optic area (MPOA) of the hypothalamus, norepinephrine facilitates, and the β-adrenoreceptor antagonist propranolol inhibits, male copulation. The present experiment tested whether chronic exercise mitigates copulatory decrements induced by adrenergic blockade in the MPOA. It was hypothesized that 3 weeks of activity-wheel running would (1) reverse deficits in male copulatory performance and (2) increase GAL mRNA in the MPOA after β-adrenoreceptor blockade with propranolol.Materials and methodsLong–Evans male rats were randomly assigned to three experimental groups: sedentary/propranolol, activity-wheel/propranolol, and home-cage control. Animals were chronically administered propranolol in saline vehicle (6 μm/day) via an osmotic mini-pump connected to a cannula implanted into the third ventricle. After 3 weeks of activity-wheel running, rats underwent copulatory testing. After rapid decapitation 24 h later, rat brains were analyzed utilizing in situ hybridization histochemistry for GAL mRNA in the MPOA.ResultsChronic exercise mitigated reductions in the percentage of males that intromitted and ejaculated after propranolol treatment, but there was no effect of exercise on GAL mRNA.ConclusionThe findings are consistent with noradrenergic adaptations in the MPOA that facilitate male copulation after wheel running independently of GAL mRNA expression.