Location of sympathetic postganglionic and sensory neurons innervating the testis in the male chicken

Sympathetic postganglionic and sensory neurons were labelled by injections of horseradish peroxidase into the testis of the male chicken. The total number of labelled neurons in the paravertebral, prevertebral, dorsal root and nodose ganglia was 943 on average for five chickens. Sympathetic postganglionic neurons were located in the paravertebral ganglia T3-LS3 (10% of the total number of labelled neurons), especially in T6 and T7, and in the prevertebral ganglia adjacent to the adrenal glands and aorta (19%). They were found almost ipsilaterally. No labelled neurons were observed in the dorsal motor nucleus of the vagus. Sensory neurons were found bilaterally in the dorsal root ganglia T2-LS3 (71%), especially in T5 to T7. Over a quarter of labelled sensory neurons were located in the contralateral dorsal root ganglia. In the nodose ganglia, only a few labelled sensory neurons were observed (much less than 1%). These results indicate that, unlike the ovary, the testis of the chicken tends to be innervated by ipsilaterally located sympathetic postganglionic and sensory neurons, with the sensory neurons being more numerous than the sympathetic postganglionic neurons.