William G. Dail

The major ganglion in the pelvic plexus of the male rat: a histochemical and ultrastructural study.

SummaryTo further evaluate the role of autonomic ganglia in the regulation of pelvic visceral activity, the neural elements in the major pelvic ganglion of the male rat have been studied with histochemical and electron microscopic techniques. The principal findings are that the ganglion is composed of cholinergic and adrenergic ganglion cells as well as small intensely fluorescent (SIF) cells. Polarity in the ganglion is indicated by clustering of small ganglion cells which stain intensely for acetylcholinesterase (AChE) along the pelvic nerve while larger cells, with weak to moderate AChE activity, collect near small branches of the hypogastric nerve. Some cholinergic ganglion cells are enclosed by a plexus of adrenergic terminals. SIF cells appear to be in contact with both cholinergic and adrenergic cells, although many of the fluorescent beads around adrenergic neurons may be short dendrites of ganglion cells, rather than processes of SIF cells. Two types of SIF cells may be distinguished on the basis of size and morphology of their granulated vesicles. Afferent synapses of the cholinergic type were common on SIF cells of the large granule and small granule type. Portions of SIF cells with large granules occur within the capsule of ganglion cells. Contacts seen here were interpreted as efferent synapses from SIF cells to the dendrites of ganglion cells.

The locus coeruleus and cerebral metabolism: Recovery of function after cortical injury

Cerebral metabolic effects of locus coeruleus (LC) lesion or drugs affecting LC were investigated after unilateral injury of sensorimotor cortex in rats. Sensoriomotor cortex ablation produced a widespread depression of cerebral 14C-2-deoxyglucose utilization which was reversed by amphetamine (AMP, 2 mg/kg) and worsened by haloperidol (HAL, 0.4 mg/kg). Lesion of LC alone did not affect cerebral oxidative metabolism, measured by a stain for the enzyme alpha-glycerophosphate dehydrogenase (α-GPDH). Lesion of LC prior to undercut laceration of motor cortex shortened time to onset of α-GPDH cortical paling. Treatment with AMP (2 mg/kg) blocked cortical paling of the enzyme stain at 4 days postinjury, an effect prevented by concomitant HAL (0.3 or 0.6 mg/kg). Apomorphine (1 mg/kg) did not block cortical paling. These data parallel effects of these drugs on recovery of function. The results suggest that a metabolic “remote functional depression” (RFD) is alleviated by catecholamine activation after cortical injury, whereas onset of RFD is accelerated by LC lesions and exacerbated by catecholamine blockade.

The hypogastric nerve innervates a population of penile neurons in the pelvic plexus.

Retrograde dye staining, enkephalin immunocytochemistry and nerve lesion paradigms were used to determine if penile neurons in the pelvic plexus are innervated by fibers in the hypogastric nerve. In the intact major pelvic ganglion of the rat, some 80% of penile neurons are enclosed by an enkephalin-positive fiber plexus. Following surgical interruption of the pelvic nerve, 20% of penile neurons were still surrounded by an enkephalin plexus. After interruption of the pelvic nerve and the hypogastric nerve, the enkephalin plexus in the ganglion was virtually absent, including the plexus around penile neurons. Therefore, possible intrinsic sources of the enkephalin fibers such as enkephalin-positive principal neurons and small intensely fluorescent cells, do not account for the delicate enkephalin fiber system in the pelvic ganglion. It is concluded that the pelvic nerve is the major source of preganglionic innervation to penile neurons in the major pelvic ganglion. However, it is significant that the hypogastric nerve is preganglionic to about 20% of penile neurons. The pathway through the hypogastric nerve may represent an alternate vasodilator system to penile erectile tissue.

Penile erection in the rat: Stimulation of the hypogastric nerve elicits increases in penile pressure after chronic interruption of the sacral parasympathetic outflow

Penile erection, a vascular event mediated by the autonomic nervous system, is often adversely affected by injury to the spinal cord. To further characterize the laboratory rat as an animal model of penile erection and to investigate erectile responses following neural injury, the present study has examined pressor penile responses in intact rats and in animals deprived of sacral parasympathetic outflow. Increases in penile pressure result from graded stimulation of postganglionic parasympathetic fibers. The vasodilator response is insensitive to blockade with atropine, a cholinergic antagonist. Penile tumescence also results from stimulation of the pelvic nerve, but not the hypogastric nerve. However, beginning 3 days after unilateral interruption of the pelvic nerve, stimulation of the ipsilateral hypogastric nerve results in an increase in penile pressure. This novel response, which is blocked by a ganglionic antagonist, is maximally developed at 1 week post-lesion, is stable for at least 3 months and remains confined to the side of the lesion. These results suggest that the rat, although relatively small, can be used to obtain quantitative data on penile erection. Moreover, the model may lend itself to an analysis of the mechanisms of altered control of visceral tissues following injury to the nervous system.

Responses to cortical injury: II. Widespread depression of the activity of an enzyme in cortex remote from a focal injury

As a part of a broader study of the reaction of the brain to injury, we report here an interesting loss of the activity of an enzyme in areas quite remote from the site of direct injury. At 36 h following a laceration or contusion injury to the hindpaw area of the motor cortex, a peculiar loss of staining for the enzyme alpha glycerophosphate dehydrogenase (alpha-GPDH) was noted. alpha-GPDH activity was markedly depressed in cortical layers II and III throughout the hemisphere on the side of the injury. The depression of alpha-GPDH activity extended far laterally across the rhinal fissure into the pyriform cortex. The decrease in alpha-GPDH staining was prominent 4 days after the injury: however, the staining pattern had returned to normal at 9 days. Enzyme changes in animals lesioned in the occipital cortex paralleled that seen in animals with a lesion in the motor cortex. Animals which had received an undercut lesion in the motor cortex 56 days earlier were contused in the occipital cortex. The old injury site presented the same sequelae of changes as seen in other lesioned animals. Additionally, a suction ablation injury involving only a small part of motor cortex resulted in the same widespread reduction of staining for alpha-GPDH in layers II and III. The derangement in energy metabolism suggests that cells in layers II and III of the cerebral cortex may be particularly vulnerable to perturbations induced by cortical trauma. These findings may be related to the diffuse and transient functional losses observed after head injury in man.

Neural and endothelial nitric oxide synthase activity in rat penile erectile tissue

NADPH-diaphorase (NADPH-D) activity and immunoreactivity for neural and endothelial nitric oxide synthase (nNOS and eNOS, respectively) were used to investigate nitric oxide (NO) regulation of penile vasculature. Both the histochemical and immunohistochemical techniques for NOS showed that all smooth muscles regions of the penis (dorsal penile artery and vein, deep penile vessels, and cavernosal muscles) were richly innervated. The endothelium of penile arteries, deep dorsal penile vein, and select veins in the crura and shaft were also stained for NADPH-D and eNOS. However, the endothelium of cavernous sinuses was unstained by both techniques. Fewer fibers were seen in the glans penis, those present being associated with small blood vessels and large nerve bundles near the trabecular walls. All penile neurons in the pelvic plexus, located by retrograde transport of a dye placed in the corpora cavernosa penis, were stained by the NADPH-D method. Essentially similar results were obtained with an antibody to nNOS. These data suggest that penile parasympathetic neurons comprise a uniform population, as all seem capable of forming nitric oxide. However, in contrast to the endothelium of penile vessels, the endothelium lining the cavernosal spaces may not be capable of nitric oxide synthesis.

The hypogastric nerve pathway to penile erectile tissue: histochemical evidence supporting a vasodilator role

Retrograde dye staining, combined with histochemical and immunohistochemical techniques, were used to characterize penile neurons in the major pelvic ganglion of the rat. Of the penile neurons 92% were immunoreactive for vasoactive intestinal polypeptide, while 95% of penile neurons stained intensely for acetylcholinesterase. None of the neurons were immunoreactive for tyrosine hydroxylase. Penile neurons in the pelvic plexus receive preganglionic input from the pelvic and the hypogastric nerve, yet the shared histochemical features of the postganglionic neurons suggest that the two pathways have a similar role in penile erectile tissue.

Innervation of the anococcygeus muscle of the rat

SummaryThe innervation of the anococcygeus muscle of the rat was investigated with regard to the histochemical features of nerve fibers within the muscle and to the location of the postganglionic autonomic neurons which are the source of these fibers. Acetylcholinesterase-positive fibers and catecholaminergic fibers are abundant in the anococcygeus as well as the related retractor penis muscle. Neuronal somata, either between muscle bundles of the anococcygeus or in the connective tissue sheath, are also acetylcholinesterase-positive. Nerve fibers and a minority of the ganglion cells in the anococcygeus and retractor penis muscles are immunoreactive for vasoactive intestinal polypeptide. Injection of the retrogradely transported dye Fluorogold into the anococcygeus muscle filled neurons in the abdominopelvic sympathetic chain, pelvic plexus and a small number of neurons in the inferior mesenteric ganglion. In the pelvic plexus, some neurons were located in the major pelvic ganglion but most were found along the main penile nerve and its branches to the anococcygeus muscle. Immunocytochemistry of these identified neurons indicates that about one half of them are positive for vasoactive intestinal polypeptice. These results raise the possibility that both acetylcholine and vasoactive intestinal polypeptide are important neurotransmitters in autonomic nerves to the anococcygeus muscle.

NADPH diaphorase innervation of the rat anococcygeus and retractor penis muscles.

NADPH diaphorase histochemistry was used to determine whether the rat anoocccygeus (AC) and retractor penis (RP) muscles are innervated by nerves capable of synthesizing nitric oxide. In both tissues, muscle fascicles were enclosed by a varicose plexus of NADPH diaphorase positive (ND+) fibers. Perikarya of neurons on the surface of the AC muscle were also intensely stained for NADPH diaphorase. Many AC-RP ganglion cells in the pelvic plexus, located by the retrograde tracer Fluorogold, also stained for the enzyme. However, a significant population of AC-RP neurons in this location remained unstained. These results provide further evidence that nitric oxide may be an important neurotransmitter in these tissues.

Morphology and Physiology of the McLeod Erythrocyte

Abstract. The McLeod phenotype is a rare condition characterized by deficiencies in the Kell blood group antigens of erythrocytes. The present study has defined some of the morphological and physiological characteristics of these red cells.